v10.3.3 release notes

Fixes #607

.coveragerc

@@ -1,9 +1,16 @@
-# Coverage isn't really compatible with subprocesses so results are unreliable
+[paths]
+source =
+	src
+	*/site-packages
 
 [run]
-branch = True
-#concurrency = multiprocessing
-source = ocrmypdf/
+branch = true
+parallel = true
+concurrency =
+	thread
+	multiprocessing
+source =
+	src/ocrmypdf
 
 [report]
 exclude_lines =
@@ -14,3 +21,4 @@ exclude_lines =
 	if 0:
 	if False:
 	if __name__ == .__main__.:
+	if TYPE_CHECKING:

.docker/Dockerfile

@@ -1,16 +1,60 @@
 # OCRmyPDF
 #
-FROM      ubuntu:18.04
+FROM ubuntu:20.04 as base
+
+FROM base as builder
+
+ENV LANG=C.UTF-8
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
   build-essential autoconf automake libtool \
   libleptonica-dev \
   zlib1g-dev \
-  libexempi3 \
-  ocrmypdf \
+  python3 \
+  python3-distutils \
+  ca-certificates \
+  curl \
+  git
+
+# Get the latest pip (Ubuntu version doesn't support manylinux2010)
+RUN \
+  curl https://bootstrap.pypa.io/get-pip.py | python3
+
+# Compile and install jbig2
+# Needs libleptonica-dev, zlib1g-dev
+RUN \
+  mkdir jbig2 \
+  && curl -L https://github.com/agl/jbig2enc/archive/ea6a40a.tar.gz | \
+  tar xz -C jbig2 --strip-components=1 \
+  && cd jbig2 \
+  && ./autogen.sh && ./configure && make && make install \
+  && cd .. \
+  && rm -rf jbig2
+
+COPY . /app
+
+WORKDIR /app
+
+RUN pip3 install --no-cache-dir \
+  -r requirements/main.txt \
+  -r requirements/webservice.txt \
+  -r requirements/test.txt \
+  -r requirements/watcher.txt \
+  .
+
+FROM base
+
+ENV LANG=C.UTF-8
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+  ghostscript \
+  img2pdf \
+  liblept5 \
+  libsm6 libxext6 libxrender-dev \
+  zlib1g \
   pngquant \
-  python3-pip \
-  python3-venv \
+  python3 \
+  qpdf \
   tesseract-ocr \
   tesseract-ocr-chi-sim \
   tesseract-ocr-deu \
@@ -18,55 +62,20 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   tesseract-ocr-fra \
   tesseract-ocr-por \
   tesseract-ocr-spa \
-  unpaper \
-  wget
+  unpaper
 
+WORKDIR /app
 
-ENV LANG=C.UTF-8
+COPY --from=builder /usr/local/lib/ /usr/local/lib/
+COPY --from=builder /usr/local/bin/ /usr/local/bin/
 
-# Compile and install jbig2
-# Needs libleptonica-dev, zlib1g-dev
-RUN \
-  mkdir jbig2 \
-  && wget -q https://github.com/agl/jbig2enc/archive/0.29.tar.gz -O - | \
-      tar xz -C jbig2 --strip-components=1 \
-  && cd jbig2 \
-  && ./autogen.sh && ./configure && make && make install \
-  && cd .. \
-  && rm -rf jbig2
+COPY --from=builder /app/misc/webservice.py /app/
+COPY --from=builder /app/misc/watcher.py /app/
 
-RUN apt-get remove -y autoconf automake libtool
+# Copy minimal project files to get the test suite.
+COPY --from=builder /app/setup.cfg /app/setup.py /app/README.md /app/
+COPY --from=builder /app/requirements /app/requirements
+COPY --from=builder /app/tests /app/tests
+COPY --from=builder /app/src /app/src
 
-RUN python3 -m venv --system-site-packages /appenv
-
-# This installs the latest binary wheel instead of the code in the current
-# folder. Installing from source will fail, apparently because cffi needs
-# build-essentials (gcc) to do a source installation
-# (i.e. "pip install ."). It's unclear to me why this is the case.
-RUN . /appenv/bin/activate; \
-  pip install --upgrade pip \
-  && pip install --upgrade ocrmypdf
-
-# Now copy the application in, mainly to get the test suite.
-# Do this now to make the best use of Docker cache.
-COPY . /application
-RUN . /appenv/bin/activate; \
-  pip install -r /application/requirements/test.txt
-
-# Remove the junk, including the source version of application since it was
-# already installed
-RUN rm -rf /tmp/* /var/tmp/* /root/* /application/ocrmypdf \
-  && apt-get remove -y build-essential \
-  && apt-get autoremove -y \
-  && apt-get autoclean -y
-
-RUN useradd docker \
-  && mkdir /home/docker \
-  && chown docker:docker /home/docker
-
-USER docker
-WORKDIR /home/docker
-
-# Must use array form of ENTRYPOINT
-# Non-array form does not append other arguments, because that is "intuitive"
-ENTRYPOINT ["/application/.docker/docker-wrapper.sh"]
+ENTRYPOINT ["/usr/local/bin/ocrmypdf"]

.docker/alpine.dockerfile

@@ -1,84 +0,0 @@
-FROM alpine:3.9 as base
-
-FROM base as builder
-
-ENV LANG=C.UTF-8
-
-RUN \
-  echo '@testing http://nl.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories \
-  # Add runtime dependencies
-  && apk add --update \
-    python3-dev \
-    py3-setuptools \
-    jbig2enc@testing \
-    ghostscript \
-    qpdf \
-    tesseract-ocr \
-    unpaper \
-    pngquant \
-    libxml2-dev \
-    libxslt-dev \
-    zlib-dev \
-    qpdf-dev \
-    libffi-dev \
-    leptonica-dev \
-    binutils \
-  # Install pybind11 for pikepdf
-  && pip3 install pybind11 \
-  # Install flask for the webservice
-  && pip3 install flask \
-  # Add build dependencies
-  && apk add --virtual build-dependencies \
-    build-base \
-    git
-
-COPY . /app
-
-WORKDIR /app
-
-RUN pip3 install .
-
-FROM base
-
-ENV LANG=C.UTF-8
-
-RUN \
-  echo '@testing http://nl.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories \
-  # Add runtime dependencies
-  && apk add --update \
-    python3 \
-    jbig2enc@testing \
-    ghostscript \
-    qpdf \
-    tesseract-ocr \
-    tesseract-ocr-data-deu \
-    tesseract-ocr-data-chi_sim \
-    unpaper \
-    pngquant \
-    libxml2 \
-    libxslt \
-    zlib \
-    qpdf \
-    libffi \
-    leptonica-dev \
-    binutils \
-  && mkdir /app
-
-WORKDIR /app
-
-# Copy build artifacts (python site-packages9
-COPY --from=builder /usr/lib/python3.6/site-packages /usr/lib/python3.6/site-packages
-COPY --from=builder /usr/bin/ocrmypdf /usr/bin/dumppdf.py /usr/bin/latin2ascii.py /usr/bin/pdf2txt.py /usr/bin/img2pdf /usr/bin/chardetect /usr/bin/
-
-# Copy
-COPY --from=builder /app/.docker/webservice.py /app/
-
-# Copy minimal project files to get the test suite.
-COPY --from=builder /app/setup.cfg /app/setup.py /app/README.md /app/
-COPY --from=builder /app/requirements /app/requirements
-COPY --from=builder /app/tests /app/tests
-COPY --from=builder /app/src /app/src
-# Copy PKG-INFO from build artifact in app dir to make setuptools-scm happy
-RUN cp /usr/lib/python3.6/site-packages/ocrmypdf-*.egg-info/PKG-INFO /app
-
-ENTRYPOINT ["/usr/bin/ocrmypdf"]

.docker/docker-wrapper.sh

@@ -1,5 +0,0 @@
-#!/bin/bash
-
-. /appenv/bin/activate
-cd /home/docker
-exec ocrmypdf "$@"

.docker/polyglot.dockerfile

@@ -1,17 +0,0 @@
-# OCRmyPDF polyglot
-#
-FROM      jbarlow83/ocrmypdf:latest
-
-USER root
-
-# Update system and install our dependencies
-RUN apt-get update && apt-get install -y --no-install-recommends \
-  tesseract-ocr-all 
-
-RUN apt-get autoremove -y && apt-get clean -y
-
-USER docker
-
-# Must use array form of ENTRYPOINT
-# Non-array form does not append other arguments, because that is "intuitive"
-ENTRYPOINT ["/application/.docker/docker-wrapper.sh"]

.docker/webservice.dockerfile

@@ -1,24 +0,0 @@
-# OCRmyPDF webservice
-#
-FROM      jbarlow83/ocrmypdf-polyglot:latest
-
-USER root
-
-# Update system and install our dependencies
-RUN apt-get update && apt-get install -y --no-install-recommends \
-  python3-flask
-
-RUN apt-get autoremove -y && apt-get clean -y
-
-EXPOSE 5000
-
-COPY .docker/webservice.py /application
-
-USER docker
-
-VOLUME ["/config"]
-
-# This config file is optional
-ENV OCRMYPDF_WEBSERVICE_SETTINGS "/config/config.py"
-
-ENTRYPOINT ["python3", "/application/webservice.py"]

.dockerignore

@@ -1,26 +1,44 @@
+# dotfiles
+.*
+!.coveragerc
+!.dockerignore
+!.git_archival.txt
+!.gitattributes
+!.gitignore
+!.pre-commit-config.yaml
+!.readthedocs.yml
+
+# Dev scratch
 *.ipynb
-*.pdf
-*.pyc
-*.rst
-*.sublime*
 **/*.pyc
-.*/
-!.git/
-!.docker/
-.ruffus_history.sqlite
-bin/
-build/
-docs/
-dist/
-htmlcov/
-include/
-lib/
-MANIFEST.in
-ocrmypdf.egg-info/
-staging/
-tests/cache/
-tests/output/
+/*.pdf
+/*.qdf
+/*.png
+/scratch.py
+IDEAS
+log/
 tests/resources/private/
 tmp/
 venv*/
+/debug_tests.py
+*.traineddata
+/private
+
+# Package building
+*.egg-info/
+build/
+dist/
 wheelhouse/
+pip-wheel-metadata/
+
+# Code coverage
+htmlcov/
+
+# Docker specific
+bin/
+docs/
+include/
+lib/
+
+# Docker include .git/
+!.git/

.gitattributes

@@ -9,5 +9,6 @@
 *.png	binary
 *.jpg	binary
 *.bin   binary
+*.afdesign  binary
 
 .git_archival.txt  export-subst

.github/FUNDING.yml

@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+patreon: # Replace with a single Patreon username
+open_collective: james-barlow
+ko_fi: # Replace with a single Ko-fi username
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+otechie: # Replace with a single Otechie username
+custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,40 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+What command line or API call were you trying to run?
+
+```bash
+ocrmypdf  ...arguments... input.pdf output.pdf
+```
+
+Run with verbosity or higher `-v1` to see more detailed logging. This information may be helpful.
+
+**Example file**
+Include an input PDF or image that demonstrates your issue.
+
+Please provide an input file with no personal or confidential information. At your option you may `GPG-encrypt the file <https://github.com/jbarlow83/OCRmyPDF/wiki>` for OCRmyPDF's author only.
+
+Links to files hosted elsewhere are perfectly acceptable. You could also look in ``tests/resources`` and see if any of those files reproduce your issue.
+
+(Exceptions: Issues with installation, command line argument parsing, test suite failures.Issues without example files usually cannot be resolved.)
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**System**
+ - OS: [e.g. Linux, Windows, macOS]
+ - OCRmyPDF Version: ``ocrmypdf --version``
+ - How did you install ocrmypdf? Did you use a system package manager, `pip`, or a Docker image?

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,17 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: enhancement
+assignees: ''
+
+---
+
+**Is your feature request related to a problem? Please describe.**
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+
+**Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.

.gitignore

@@ -1,18 +1,38 @@
-# Development environment
-.bash_history
-.pylintrc
-.pytest_cache/
-.ruffus_history.sqlite
-.venv/
-*.pyc
-*.sublime-*
+# dotfiles
+.*
+!.coveragerc
+!.dockerignore
+!.git_archival.txt
+!.gitattributes
+!.gitignore
+!.pre-commit-config.yaml
+!.readthedocs.yml
+
+# Dev scratch
+*.ipynb
+**/*.pyc
+/*.pdf
+/*.qdf
+/*.png
+/scratch.py
+IDEAS
+log/
+tests/resources/private/
+tmp/
+venv*/
+/debug_tests.py
+*.traineddata
+/private
 
 # Package building
-.eggs/
 *.egg-info/
 build/
 dist/
 wheelhouse/
+pip-wheel-metadata/
+
+# Code coverage
+htmlcov/
 
 # Automatically generated files
 docs/_build/
@@ -20,24 +40,3 @@ docs/_static/
 docs/_templates/
 docs/Makefile
 ocrmypdf/lib/_*.py
-
-# Code coverage
-.coverage*
-htmlcov/
-
-# Testing
-.ipynb_checkpoints/
-.vscode/
-*.ipynb
-*.profile
-/*.pdf
-/*.qdf
-/*.png
-/scratch.py
-IDEAS
-log/
-tests/output/
-tests/resources/private/
-tmp/
-/debug_tests.py
-*.traineddata

.pre-commit-config.yaml

@@ -1,6 +1,23 @@
 repos:
--   repo: https://github.com/ambv/black
-    rev: stable
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.1.0
     hooks:
-    - id: black
-      language_version: python3.6
+      - id: check-case-conflict
+      - id: check-merge-conflict
+      - id: check-toml
+      - id: check-yaml
+      - id: debug-statements
+  - repo: https://github.com/asottile/seed-isort-config
+    rev: v2.2.0
+    hooks:
+      - id: seed-isort-config
+  - repo: https://github.com/pre-commit/mirrors-isort
+    rev: v5.0.5 # pick the isort version you'd like to use from https://github.com/pre-commit/mirrors-isort/releases
+    hooks:
+      - id: isort
+  - repo: https://github.com/psf/black
+    rev: 19.10b0
+    hooks:
+      - id: black
+        language_version: python3.8
+        exclude: ^src/ocrmypdf/lib/_leptonica.py

.travis.yml

@@ -1,146 +0,0 @@
-cache:
-  pip: true
-  directories:
-  - $HOME/Library/Caches/Homebrew
-
-matrix:
-  include:
-    - os: linux
-      dist: trusty
-      sudo: required
-      language: python
-      python: "3.6"
-      env:
-        - DIST=trusty
-      addons: &trusty_apt
-        apt:
-          update: true
-          sources:
-          - sourceline: 'ppa:alex-p/tesseract-ocr'
-          - sourceline: 'ppa:heyarje/libav-11'
-          - sourceline: 'ppa:vshn/ghostscript'
-          packages:
-          - ghostscript
-          - libavcodec56
-          - libavformat56
-          - libavutil54
-          - libexempi3
-          - libffi-dev
-          - pngquant
-          - poppler-utils
-          - qpdf
-          - tesseract-ocr
-          - tesseract-ocr-deu
-          - tesseract-ocr-eng
-          - tesseract-ocr-fra
-    - os: linux
-      dist: xenial
-      sudo: required
-      language: python
-      python: "3.7"
-      env:
-        - DIST=xenial
-      addons:
-        apt:
-          update: true
-          sources:
-          - sourceline: 'ppa:alex-p/tesseract-ocr'
-          packages:
-          - ghostscript
-          - libexempi3
-          - libffi-dev
-          - pngquant
-          - poppler-utils
-          - qpdf
-          - tesseract-ocr
-          - tesseract-ocr-deu
-          - tesseract-ocr-eng
-          - tesseract-ocr-fra
-          - unpaper
-    - os: osx
-      osx_image: xcode9.2
-      language: generic
-      addons:
-        homebrew:
-          update: true
-          packages:
-            - exempi
-            - ghostscript
-            - jbig2enc
-            - leptonica
-            - openjpeg
-            - pngquant
-            - python
-            - qpdf
-            - tesseract
-            - unpaper
-    - os: osx
-      osx_image: xcode9.2
-      language: generic
-      env:
-        - ADD_PDFMINER=1
-      addons:
-        homebrew:
-          update: true
-          packages:
-            - exempi
-            - ghostscript
-            - jbig2enc
-            - leptonica
-            - openjpeg
-            - pngquant
-            - python
-            - qpdf
-            - tesseract
-            - unpaper
-
-before_cache:
-- rm -f $HOME/.cache/pip/log/debug.log
-
-before_install: |
-  mkdir -p bin
-  if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
-    pip3 install --upgrade pip
-    pip3 install --upgrade wheel
-    if [[ "$DIST" == "trusty" ]]; then
-      mkdir -p packages
-      wget -q 'https://www.dropbox.com/s/vaq0kbwi6e6au80/unpaper_6.1-1.deb?raw=1' -O packages/unpaper_6.1-1.deb
-      sudo dpkg -i packages/unpaper_6.1-1.deb
-    fi
-  elif [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
-    pip3 install --upgrade pip
-    pip3 install wheel
-  fi
-
-install:
-- export PATH=$PWD/bin:$PATH
-- pip3 install pycparser  # py3.7 workaround for https://github.com/eliben/pycparser/issues/251
-- pip3 install -r requirements/main.txt
-- pip3 install --no-deps .
-- |
-  if [[ "$ADD_PDFMINER" == "1" ]]; then
-    pip3 install --no-deps .[pdfminer]
-  fi
-- pip3 install -r requirements/test.txt
-
-script:
-- tesseract --version
-- qpdf --version
-- pytest -n auto
-
-deploy:
-  # release for main pypi
-  # 3.6 is considered the build leader and does the deploy, otherwise there is
-  # a race and all versions will try to deploy
-  # OTOH if we ever need separate binary wheels then each version needs its
-  # own deploy
-- provider: pypi
-  user: ocrmypdf-travis
-  password:
-    secure: "DTFOmmNL6olA0+yXvp4u9jXZlZeqrJsJ0526jzqf4a3gZ6jnGTq5UI6WzRsslSyoMMfXKtHQebqHM6ogSgCZinyZ3ufHJo8fn9brxbEc2gsiWkbj5o3bGwdWMT1vNNE7XW0VCpw87rZ1EEwjl4FJHFudMlPR1yfU5+uq0k0PACo="
-  distributions: "sdist bdist_wheel"
-  on:
-    branch: master
-    tags: true
-    condition: $TRAVIS_PYTHON_VERSION == "3.6" && $TRAVIS_OS_NAME == "linux"
-  skip_upload_docs: true

MANIFEST.in

@@ -1,43 +0,0 @@
-# requirements
-recursive-include requirements *
-
-# git
-include .git_archival.txt
-
-# docker
-include .dockerignore
-recursive-include .docker *
-
-# tests
-include .coveragerc
-recursive-include tests *.bin
-recursive-include tests *.jpg
-recursive-include tests *.jsonl
-recursive-include tests *.png
-recursive-include tests *.pdf
-recursive-include tests *.py
-recursive-include tests *.rst
-recursive-include tests *.txt
-recursive-exclude tests/resources/private *
-
-# documentation
-include LICENSE
-include *.rst
-recursive-exclude .github *
-recursive-include docs *.py
-recursive-include docs *.rst
-recursive-include docs *.svg
-recursive-exclude docs/_build *
-
-
-# support files
-recursive-include src/ocrmypdf/data *
-include *.py
-exclude tasks.py
-recursive-exclude .travis *
-exclude .travis*
-
-
-# code
-exclude src/ocrmypdf/lib/_leptonica.py
-exclude scratch.py

README.md

@@ -1,15 +1,13 @@
-OCRmyPDF
-========
+<img src="docs/images/logo.svg" width="240" alt="OCRmyPDF">
 
-[![Travis build status][travis]](https://travis-ci.org/jbarlow83/OCRmyPDF) [![PyPI version][pypi]](https://pypi.org/project/ocrmypdf/) ![Homebrew version][homebrew] ![ReadTheDocs][docs]
+[![Build Status][azure]](https://dev.azure.com/jim0585/ocrmypdf/_build/latest?definitionId=2&branchName=master) [![PyPI version][pypi]](https://pypi.org/project/ocrmypdf/) ![Homebrew version][homebrew] ![ReadTheDocs][docs] ![Python versions][pyversions]
 
+[azure]: https://dev.azure.com/jim0585/ocrmypdf/_apis/build/status/jbarlow83.OCRmyPDF?branchName=master
 [travis]: https://travis-ci.org/jbarlow83/OCRmyPDF.svg?branch=master "Travis build status"
-
 [pypi]: https://img.shields.io/pypi/v/ocrmypdf.svg "PyPI version"
-
 [homebrew]: https://img.shields.io/homebrew/v/ocrmypdf.svg "Homebrew version"
-
 [docs]: https://readthedocs.org/projects/ocrmypdf/badge/?version=latest "RTD"
+[pyversions]: https://img.shields.io/pypi/pyversions/ocrmypdf "Supported Python versions"
 
 OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched or copy-pasted.
 
@@ -27,27 +25,25 @@ ocrmypdf                      # it's a scriptable command line program
 
 [See the release notes for details on the latest changes](https://ocrmypdf.readthedocs.io/en/latest/release_notes.html).
 
-Main features
--------------
+## Main features
 
 - Generates a searchable [PDF/A](https://en.wikipedia.org/?title=PDF/A) file from a regular PDF
 - Places OCR text accurately below the image to ease copy / paste
 - Keeps the exact resolution of the original embedded images
 - When possible, inserts OCR information as a "lossless" operation without disrupting any other content
 - Optimizes PDF images, often producing files smaller than the input file
-- If requested deskews and/or cleans the image before performing OCR
+- If requested, deskews and/or cleans the image before performing OCR
 - Validates input and output files
 - Distributes work across all available CPU cores
-- Uses [Tesseract OCR](https://github.com/tesseract-ocr/tesseract) engine
-- Supports more than [100 languages](https://github.com/tesseract-ocr/tessdata) recognized by Tesseract
-- Battle-tested on thousands of PDFs, a test suite and continuous integration
+- Uses [Tesseract OCR](https://github.com/tesseract-ocr/tesseract) engine to recognize more than [100 languages](https://github.com/tesseract-ocr/tessdata)
+- Scales properly to handle files with thousands of pages
+- Battle-tested on millions of PDFs
 
 For details: please consult the [documentation](https://ocrmypdf.readthedocs.io/en/latest/).
 
-Motivation
-----------
+## Motivation
 
-I searched the web for a free command line tool to OCR PDF files on Linux/UNIX: I found many, but none of them were really satisfying.
+I searched the web for a free command line tool to OCR PDF files: I found many, but none of them were really satisfying:
 
 - Either they produced PDF files with misplaced text under the image (making copy/paste impossible)
 - Or they did not handle accents and multilingual characters
@@ -59,10 +55,9 @@ I searched the web for a free command line tool to OCR PDF files on Linux/UNIX:
 
 ...so I decided to develop my own tool.
 
-Installation
-------------
+## Installation
 
-Linux, UNIX, and macOS are supported. Windows is not directly supported but there is a Docker image available that runs on Windows.
+Linux, Windows, macOS and FreeBSD are supported. Docker images are also available.
 
 Users of Debian 9 or later or Ubuntu 16.10 or later may simply
 
@@ -76,7 +71,7 @@ and users of Fedora 29 or later may simply
 dnf install ocrmypdf
 ```
 
-and macOS users with Homebrew may simply
+and Homebrew users (macOS, Linux, Windows Subsystem for Linux) may simply
 
 ```bash
 brew install ocrmypdf
@@ -84,8 +79,7 @@ brew install ocrmypdf
 
 For everyone else, [see our documentation](https://ocrmypdf.readthedocs.io/en/latest/installation.html) for installation steps.
 
-Languages
----------
+## Languages
 
 OCRmyPDF uses Tesseract for OCR, and relies on its language packs. For Linux users, you can often find packages that provide language packs:
 
@@ -94,15 +88,17 @@ OCRmyPDF uses Tesseract for OCR, and relies on its language packs. For Linux use
 apt-cache search tesseract-ocr
 
 # Debian/Ubuntu users
-apt-get install tesseract-ocr-chi-sim  # Example: Install Chinese Simplified language back
+apt-get install tesseract-ocr-chi-sim  # Example: Install Chinese Simplified language pack
+
+# Arch Linux users
+pacman -S tesseract-data-eng tesseract-data-deu # Example: Install the English and German language packs
 ```
 
 You can then pass the `-l LANG` argument to OCRmyPDF to give a hint as to what languages it should search for. Multiple languages can be requested.
 
-Documentation and support
--------------------------
+## Documentation and support
 
-Once ocrmypdf is installed, the built-in help which explains the command syntax and options can be accessed via:
+Once OCRmyPDF is installed, the built-in help which explains the command syntax and options can be accessed via:
 
 ```bash
 ocrmypdf --help
@@ -110,37 +106,33 @@ ocrmypdf --help
 
 Our [documentation is served on Read the Docs](https://ocrmypdf.readthedocs.io/en/latest/index.html).
 
-If you detect an issue, please:
+Please report issues on our [GitHub issues](https://github.com/jbarlow83/OCRmyPDF/issues) page, and follow the issue template for quick response.
 
-- Check whether your issue is already known
-- If no problem report exists on github, please create one here: <https://github.com/jbarlow83/OCRmyPDF/issues>
-- Describe your problem thoroughly
-- Append the console output of the script when running the debug mode (`-v 1` option)
-- If possible provide your input PDF file as well as the content of the temporary folder (using a file sharing service like Dropbox)
+## Requirements
 
-Requirements
-------------
+In addition to the required Python version (3.6+), OCRmyPDF requires external program installations of Ghostscript, Tesseract OCR, QPDF, and Leptonica. OCRmyPDF is pure Python, but uses CFFI to portably generate library bindings. OCRmyPDF works on pretty much everything: Linux, macOS, Windows and FreeBSD.
 
-Runs on CPython 3.5, 3.6 and 3.7. Requires external program installations of Ghostscript, Tesseract OCR, QPDF, and Leptonica. ocrmypdf is pure Python, but uses CFFI to portably generate library bindings.
-
-Press & Media
--------------
+## Press & Media
 
 - [Going paperless with OCRmyPDF](https://medium.com/@ikirichenko/going-paperless-with-ocrmypdf-e2f36143f46a)
 - [Converting a scanned document into a compressed searchable PDF with redactions](https://medium.com/@treyharris/converting-a-scanned-document-into-a-compressed-searchable-pdf-with-redactions-63f61c34fe4c)
-- [c't 1-2014, page 59](http://heise.de/-2279695): Detailed presentation of OCRmyPDF v1.0 in the leading German IT magazine c't
-- [heise Open Source, 09/2014: Texterkennung mit OCRmyPDF](http://heise.de/-2356670)
+- [c't 1-2014, page 59](https://heise.de/-2279695): Detailed presentation of OCRmyPDF v1.0 in the leading German IT magazine c't
+- [heise Open Source, 09/2014: Texterkennung mit OCRmyPDF](https://heise.de/-2356670)
+- [heise Durchsuchbare PDF-Dokumente mit OCRmyPDF erstellen](https://www.heise.de/ratgeber/Durchsuchbare-PDF-Dokumente-mit-OCRmyPDF-erstellen-4607592.html)
+- [Excellent Utilities: OCRmyPDF](https://www.linuxlinks.com/excellent-utilities-ocrmypdf-add-ocr-text-layer-scanned-pdfs/)
 
-License
--------
+## Business enquiries
+
+OCRmyPDF would not be the software that it is today without companies and users choosing to provide support for feature development and consulting enquiries. We are happy to discuss all enquiries, whether for extending the existing feature set, or integrating OCRmyPDF into a larger system.
+
+## License
 
 The OCRmyPDF software is licensed under the GNU GPLv3. Certain files are covered by other licenses, as noted in their source files.
 
 The license for each test file varies, and is noted in tests/resources/README.rst. The documentation is licensed under Creative Commons Attribution-ShareAlike 4.0 (CC-BY-SA 4.0).
 
-OCRmyPDF versions prior to 6.0 were licensed under the MIT License.
+OCRmyPDF versions prior to 6.0 were distributed under the MIT License.
 
-Disclaimer
-----------
+## Disclaimer
 
 The software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

azure-pipelines.yml

@@ -0,0 +1,259 @@
+trigger:
+  tags:
+    include:
+      - v*
+  branches:
+    include:
+      - "*"
+    exclude:
+      - "travis"
+
+stages:
+  - stage: "Test"
+    jobs:
+      - job: Windows
+        pool:
+          vmImage: "vs2017-win2016"
+        strategy:
+          matrix:
+            Python36:
+              python.version: "3.6"
+            Python37:
+              python.version: "3.7"
+            Python38:
+              python.version: "3.8"
+        steps:
+          - task: UsePythonVersion@0
+            inputs:
+              versionSpec: "$(python.version)"
+          - pwsh: |
+              choco install --yes --no-progress --pre tesseract
+              choco install --yes --no-progress python3
+              choco install --yes --no-progress ghostscript
+              choco install --yes --no-progress pngquant
+            displayName: "Install system packages"
+          - pwsh: |
+              refreshenv
+              python -m pip install --upgrade pip wheel
+              python -m pip install -r requirements/main.txt -r requirements/test.txt .
+            displayName: "Install Python packages"
+          - pwsh: |
+              refreshenv
+              $env:pathext += ';.py'
+              # -n auto helps Windows
+              python -m pytest -n auto --junitxml=test.xml --cov=ocrmypdf --cov-report=xml
+            displayName: "Test"
+          - task: PublishTestResults@2
+            inputs:
+              testResultsFiles: "test.xml"
+              testRunTitle: "$(Agent.OS) - $(Build.DefinitionName) - Python $(python.version)"
+            condition: succeededOrFailed()
+      - job: "Ubuntu_1804"
+        pool:
+          vmImage: "ubuntu-18.04"
+        strategy:
+          matrix:
+            Python36:
+              python.version: "3.6"
+            Python37:
+              python.version: "3.7"
+            Python38:
+              python.version: "3.8"
+        steps:
+          - task: UsePythonVersion@0
+            inputs:
+              versionSpec: "$(python.version)"
+          - bash: |
+              sudo apt-get update
+              sudo apt-get install -y --no-install-recommends \
+                python3-software-properties \
+                curl \
+                ghostscript \
+                img2pdf \
+                libexempi3 \
+                libffi-dev \
+                liblept5 \
+                libsm6 libxext6 libxrender-dev \
+                pngquant \
+                poppler-utils \
+                tesseract-ocr \
+                tesseract-ocr-deu \
+                tesseract-ocr-eng \
+                unpaper \
+                zlib1g
+            displayName: "Install system packages"
+          - bash: |
+              curl https://bootstrap.pypa.io/get-pip.py | python3
+              pip3 install -r requirements/main.txt -r requirements/test.txt .
+            displayName: "Install Python packages"
+          - bash: |
+              tesseract --version
+            displayName: "Record versions"
+          - bash: |
+              # -n auto is slower on Linux and breaks on Python 3.8
+              pytest -n0 --junitxml=test.xml --cov=ocrmypdf --cov-report=xml
+            displayName: "Test"
+          - task: PublishTestResults@2
+            inputs:
+              testResultsFiles: "test.xml"
+              testRunTitle: "$(Agent.OS) - $(Build.DefinitionName) - Python $(python.version)"
+            condition: succeededOrFailed()
+      - job: "Ubuntu_1604"
+        pool:
+          vmImage: "ubuntu-16.04"
+        strategy:
+          matrix:
+            Python36:
+              python.version: "3.6"
+        steps:
+          - task: UsePythonVersion@0
+            inputs:
+              versionSpec: "$(python.version)"
+          - bash: |
+              sudo apt-get update
+              sudo apt-get install -y --no-install-recommends \
+                software-properties-common
+              sudo add-apt-repository -y ppa:alex-p/tesseract-ocr
+              sudo apt-get update
+              sudo apt-get install -y --no-install-recommends \
+                ghostscript \
+                img2pdf \
+                libexempi3 \
+                libffi-dev \
+                liblept5 \
+                libsm6 libxext6 libxrender-dev \
+                pngquant \
+                poppler-utils \
+                tesseract-ocr \
+                tesseract-ocr-deu \
+                tesseract-ocr-eng \
+                unpaper \
+                zlib1g
+            displayName: "Install system packages"
+          - bash: |
+              curl https://bootstrap.pypa.io/get-pip.py | python3
+              pip3 install -r requirements/main.txt -r requirements/test.txt .
+            displayName: "Install Python packages"
+          - bash: |
+              tesseract --version
+            displayName: "Record versions"
+          - bash: |
+              # -n auto is slower on Linux and breaks on Python 3.8
+              pytest -n0 --junitxml=test.xml --cov=ocrmypdf --cov-report=xml
+            displayName: "Test"
+          - task: PublishTestResults@2
+            inputs:
+              testResultsFiles: "test.xml"
+              testRunTitle: "$(Agent.OS) - $(Build.DefinitionName) - Python $(python.version)"
+            condition: succeededOrFailed()
+      - job: "macOS_Mojave"
+        pool:
+          vmImage: "macos-10.14"
+        strategy:
+          matrix:
+            Python37:
+              python.version: ""
+            Python38:
+              python.version: "python@3.8"
+        steps:
+          # https://github.com/actions/virtual-environments/issues/664
+          # - task: UsePythonVersion@0
+          #   inputs:
+          #     versionSpec: "$(python.version)"
+          - bash: |
+              brew update
+              brew unlink python@2
+              if [ "$(python.version)" != "" ]; then
+                brew upgrade $(python.version)
+              else
+                echo "Using Python `python3 --version`"
+              fi
+            displayName: "Update brew and Python"
+          - bash: |
+              brew install \
+                exempi \
+                ghostscript \
+                jbig2enc \
+                leptonica \
+                openjpeg \
+                pngquant \
+                tesseract \
+                unpaper
+            displayName: "Install system packages"
+          - bash: |
+              pip3 install --upgrade pip
+              pip3 install -r requirements/main.txt -r requirements/test.txt .
+            displayName: "Install Python packages"
+          - bash: |
+              tesseract --version
+            displayName: "Record versions"
+          - bash: pytest -nauto --junitxml=test.xml --cov=ocrmypdf --cov-report=xml
+            displayName: "Test"
+          - task: PublishTestResults@2
+            inputs:
+              testResultsFiles: "test.xml"
+              testRunTitle: "$(Agent.OS) - $(Build.DefinitionName) - Python $(python.version)"
+            condition: succeededOrFailed()
+          - task: PublishCodeCoverageResults@1
+            inputs:
+              codeCoverageTool: Cobertura
+              summaryFileLocation: "$(System.DefaultWorkingDirectory)/**/coverage.xml"
+
+  - stage: "Artifacts"
+    jobs:
+      - job: "sdist_wheel"
+        pool:
+          vmImage: "ubuntu-18.04"
+        steps:
+          - task: UsePythonVersion@0
+            inputs:
+              versionSpec: "3.7"
+          - bash: |
+              python -m pip install --upgrade pip wheel
+              python setup.py sdist bdist_wheel
+          - publish: dist
+            artifact: sdist_wheel
+
+  - stage: "Deploy"
+    jobs:
+      - deployment: "PyPI"
+        pool:
+          vmImage: "ubuntu-18.04"
+        environment: "deploy"
+        strategy:
+          runOnce:
+            deploy:
+              steps:
+                - download: current
+                  artifact: sdist_wheel
+                - script: |
+                    mkdir -p dist
+                    mv $(Pipeline.Workspace)/sdist_wheel/* dist
+                  displayName: "Move dist files"
+                - task: UsePythonVersion@0
+                  inputs:
+                    versionSpec: "3.8"
+                    architecture: x64
+                - script: |
+                    pip install --upgrade twine
+                  displayName: "Generate artifacts"
+                - script: |
+                    cat <<FILE >.pypirc
+                    [distutils]
+                    index-servers =
+                        pypi
+
+                    [pypi]
+                    username: __token__
+                    password: $(TOKEN_PYPI)
+
+                    FILE
+                  displayName: "Generate PyPI auth file"
+                - script: |
+                    python -m twine upload --config-file .pypirc dist/*
+                  displayName: "Upload to PyPI"
+                  condition: and(succeeded(), startsWith(variables['Build.SourceBranch'], 'refs/tags/'))
+                - script: |
+                    curl -X POST -d "token=$(TOKEN_RTD)" https://readthedocs.org/api/v2/webhook/pikepdf/39557/
+                  displayName: "Trigger ReadTheDocs"
+                  condition: and(succeeded(), or(startsWith(variables['Build.SourceBranch'], 'refs/tags/'), startsWith(variables['Build.SourceBranch'], 'refs/heads/master')))

debian/copyright

@@ -2,7 +2,6 @@ Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
 Upstream-Name: OCRmyPDF
 Upstream-Contact: James R. Barlow <barlow.jim@gmail.com>
 Source: https://github.com/jbarlow83/OCRmyPDF
-Files-Excluded: tests/resources/milk.pdf
 
 Files: *
 Copyright:
@@ -10,10 +9,24 @@ Copyright:
  (C) 2013-2016, 2015-2017 2016, 2017, 2017-2018, 2018 James R. Barlow
 License: GPL-3+
 
+Files: misc/watcher.py
+Copyright:
+ (C) 2019 Ian Alexander: https://github.com/ianalexander
+ (C) 2020 James R. Barlow
+License: GPL-3+
+
+Files: misc/webservice.py
+Copyright: (C) 2019 James R. Barlow
+License: AGPL-3+
+
 Files: docs tests/resources/*
 Copyright: (C) 2013-2018 James R. Barlow
 License: CC-BY-SA-4.0
 
+Files: docs/images/bitmap_vs_svg.svg
+Copyright: (C) 2006 Yug
+License: CC-BY-SA-2.5
+
 Files: src/ocrmypdf/hocrtransform.py
 Copyright: (C) 2010 Jonathan Brinley <jonathanbrinley@gmail.com>
  (C) 2013-14 Julien Pfefferkorn
@@ -30,7 +43,7 @@ Copyright: (C) 2014 Armin Ronacher
  (C) 2017 James R. Barlow
 License: BSD-3-clause
 
-Files: tests/spoof/*
+Files: tests/plugins/*
 Copyright: (C) 2016, 2017, 2016-2018 James R. Barlow
 License: Expat
 
@@ -82,12 +95,17 @@ License: CC-BY-SA-3.0
 Files: tests/resources/typewriter.png tests/resources/2400dpi.pdf
 Copyright: (C) 2005 Ellywa
 License: GFDL-1.2+ or CC-BY-SA-1.0 or CC-BY-SA-2.0 or CC-BY-SA-2.5 or CC-BY-SA-3.0
+Comment:
+ Obtained from: https://commons.wikimedia.org/wiki/File:Triumph.typewriter_text_Linzensoep.gif
 
 Files: tests/resources/overlay.pdf
 Copyright: (C) 2017 Max Anderson
 License: Expat
 
-Files: tests/resources/baiona*.png
+Files:
+ tests/resources/baiona*.png
+ tests/resources/baiona*.jpg
+ tests/resources/link.pdf
 Copyright: (C) 2014 Euskaldunaa
 License: CC-BY-SA-4.0
 
@@ -95,11 +113,12 @@ Files: tests/resources/vector.pdf
 Copyright: (C) 2018 Catscratch
 License: Expat
 
-Files: test/resources/enron*.pdf
-Copyright: EnronData.org
-License: CC-BY-3.0
- See: https://enrondata.readthedocs.io/en/latest/data/edo-enron-email-pst-dataset/
-Comment: Unprocessed.
+Files: tests/resources/3small.pdf
+Copyright: (C) 2014 Euskaldunaa
+ (C) 2017 James R. Barlow
+ (C) 2005 Ellywa
+License: CC-BY-SA-4.0 and (GFDL-1.2+ or CC-BY-SA-1.0 or CC-BY-SA-2.0 or CC-BY-SA-2.5 or CC-BY-SA-3.0)
+Comment: concatenation of baiona_gray.png, crom.png and typewriter.png/2400dpi.pdf
 
 Files: src/ocrmypdf/data/sRGB.icc
 Copyright:  Kai-Uwe Behrmann <www.behrmann.name>
@@ -130,6 +149,669 @@ License: GPL-3+
  On Debian systems, the complete text of the GNU General
  Public License version 3 can be found in "/usr/share/common-licenses/GPL-3".
 
+License: AGPL-3+
+                     GNU AFFERO GENERAL PUBLIC LICENSE
+                        Version 3, 19 November 2007
+ .
+  Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+  Everyone is permitted to copy and distribute verbatim copies
+  of this license document, but changing it is not allowed.
+ .
+                             Preamble
+ .
+   The GNU Affero General Public License is a free, copyleft license for
+ software and other kinds of works, specifically designed to ensure
+ cooperation with the community in the case of network server software.
+ .
+   The licenses for most software and other practical works are designed
+ to take away your freedom to share and change the works.  By contrast,
+ our General Public Licenses are intended to guarantee your freedom to
+ share and change all versions of a program--to make sure it remains free
+ software for all its users.
+ .
+   When we speak of free software, we are referring to freedom, not
+ price.  Our General Public Licenses are designed to make sure that you
+ have the freedom to distribute copies of free software (and charge for
+ them if you wish), that you receive source code or can get it if you
+ want it, that you can change the software or use pieces of it in new
+ free programs, and that you know you can do these things.
+ .
+   Developers that use our General Public Licenses protect your rights
+ with two steps: (1) assert copyright on the software, and (2) offer
+ you this License which gives you legal permission to copy, distribute
+ and/or modify the software.
+ .
+   A secondary benefit of defending all users' freedom is that
+ improvements made in alternate versions of the program, if they
+ receive widespread use, become available for other developers to
+ incorporate.  Many developers of free software are heartened and
+ encouraged by the resulting cooperation.  However, in the case of
+ software used on network servers, this result may fail to come about.
+ The GNU General Public License permits making a modified version and
+ letting the public access it on a server without ever releasing its
+ source code to the public.
+ .
+   The GNU Affero General Public License is designed specifically to
+ ensure that, in such cases, the modified source code becomes available
+ to the community.  It requires the operator of a network server to
+ provide the source code of the modified version running there to the
+ users of that server.  Therefore, public use of a modified version, on
+ a publicly accessible server, gives the public access to the source
+ code of the modified version.
+ .
+   An older license, called the Affero General Public License and
+ published by Affero, was designed to accomplish similar goals.  This is
+ a different license, not a version of the Affero GPL, but Affero has
+ released a new version of the Affero GPL which permits relicensing under
+ this license.
+ .
+   The precise terms and conditions for copying, distribution and
+ modification follow.
+ .
+                        TERMS AND CONDITIONS
+ .
+   0. Definitions.
+ .
+   "This License" refers to version 3 of the GNU Affero General Public License.
+ .
+   "Copyright" also means copyright-like laws that apply to other kinds of
+ works, such as semiconductor masks.
+ .
+   "The Program" refers to any copyrightable work licensed under this
+ License.  Each licensee is addressed as "you".  "Licensees" and
+ "recipients" may be individuals or organizations.
+ .
+   To "modify" a work means to copy from or adapt all or part of the work
+ in a fashion requiring copyright permission, other than the making of an
+ exact copy.  The resulting work is called a "modified version" of the
+ earlier work or a work "based on" the earlier work.
+ .
+   A "covered work" means either the unmodified Program or a work based
+ on the Program.
+ .
+   To "propagate" a work means to do anything with it that, without
+ permission, would make you directly or secondarily liable for
+ infringement under applicable copyright law, except executing it on a
+ computer or modifying a private copy.  Propagation includes copying,
+ distribution (with or without modification), making available to the
+ public, and in some countries other activities as well.
+ .
+   To "convey" a work means any kind of propagation that enables other
+ parties to make or receive copies.  Mere interaction with a user through
+ a computer network, with no transfer of a copy, is not conveying.
+ .
+   An interactive user interface displays "Appropriate Legal Notices"
+ to the extent that it includes a convenient and prominently visible
+ feature that (1) displays an appropriate copyright notice, and (2)
+ tells the user that there is no warranty for the work (except to the
+ extent that warranties are provided), that licensees may convey the
+ work under this License, and how to view a copy of this License.  If
+ the interface presents a list of user commands or options, such as a
+ menu, a prominent item in the list meets this criterion.
+ .
+   1. Source Code.
+ .
+   The "source code" for a work means the preferred form of the work
+ for making modifications to it.  "Object code" means any non-source
+ form of a work.
+ .
+   A "Standard Interface" means an interface that either is an official
+ standard defined by a recognized standards body, or, in the case of
+ interfaces specified for a particular programming language, one that
+ is widely used among developers working in that language.
+ .
+   The "System Libraries" of an executable work include anything, other
+ than the work as a whole, that (a) is included in the normal form of
+ packaging a Major Component, but which is not part of that Major
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+ "Major Component", in this context, means a major essential component
+ (kernel, window system, and so on) of the specific operating system
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+ produce the work, or an object code interpreter used to run it.
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+ programs which are used unmodified in performing those activities but
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+ such as by intimate data communication or control flow between those
+ subprograms and other parts of the work.
+ .
+   The Corresponding Source need not include anything that users
+ can regenerate automatically from other parts of the Corresponding
+ Source.
+ .
+   The Corresponding Source for a work in source code form is that
+ same work.
+ .
+   2. Basic Permissions.
+ .
+   All rights granted under this License are granted for the term of
+ copyright on the Program, and are irrevocable provided the stated
+ conditions are met.  This License explicitly affirms your unlimited
+ permission to run the unmodified Program.  The output from running a
+ covered work is covered by this License only if the output, given its
+ content, constitutes a covered work.  This License acknowledges your
+ rights of fair use or other equivalent, as provided by copyright law.
+ .
+   You may make, run and propagate covered works that you do not
+ convey, without conditions so long as your license otherwise remains
+ in force.  You may convey covered works to others for the sole purpose
+ of having them make modifications exclusively for you, or provide you
+ with facilities for running those works, provided that you comply with
+ the terms of this License in conveying all material for which you do
+ not control copyright.  Those thus making or running the covered works
+ for you must do so exclusively on your behalf, under your direction
+ and control, on terms that prohibit them from making any copies of
+ your copyrighted material outside their relationship with you.
+ .
+   Conveying under any other circumstances is permitted solely under
+ the conditions stated below.  Sublicensing is not allowed; section 10
+ makes it unnecessary.
+ .
+   3. Protecting Users' Legal Rights From Anti-Circumvention Law.
+ .
+   No covered work shall be deemed part of an effective technological
+ measure under any applicable law fulfilling obligations under article
+ 11 of the WIPO copyright treaty adopted on 20 December 1996, or
+ similar laws prohibiting or restricting circumvention of such
+ measures.
+ .
+   When you convey a covered work, you waive any legal power to forbid
+ circumvention of technological measures to the extent such circumvention
+ is effected by exercising rights under this License with respect to
+ the covered work, and you disclaim any intention to limit operation or
+ modification of the work as a means of enforcing, against the work's
+ users, your or third parties' legal rights to forbid circumvention of
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  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the

docs/advanced.rst

@@ -1,16 +1,34 @@
+=================
 Advanced features
 =================
 
 Control of unpaper
-------------------
+==================
 
-OCRmyPDF uses ``unpaper`` to provide the implementation of the ``--clean`` and ``--clean-final`` arguments. `unpaper <https://github.com/Flameeyes/unpaper/blob/master/doc/basic-concepts.md>`_ provides a variety of image processing filters to improve images.
+OCRmyPDF uses ``unpaper`` to provide the implementation of the
+``--clean`` and ``--clean-final`` arguments.
+`unpaper <https://github.com/Flameeyes/unpaper/blob/master/doc/basic-concepts.md>`__
+provides a variety of image processing filters to improve images.
 
-By default, OCRmyPDF uses only ``unpaper`` arguments that were found to be safe to use on almost all files without having to inspect every page of the file afterwards. This is particularly true when only ``--clean`` is used, since that instructs OCRmyPDF to only clean the image before OCR and not the final image.
+By default, OCRmyPDF uses only ``unpaper`` arguments that were found to
+be safe to use on almost all files without having to inspect every page
+of the file afterwards. This is particularly true when only ``--clean``
+is used, since that instructs OCRmyPDF to only clean the image before
+OCR and not the final image.
 
-However, if you wish to use the more aggressive options in ``unpaper``, you may use ``--unpaper-args '...'`` to override the OCRmyPDF's defaults and forward other arguments to unpaper. This option will forward arguments to ``unpaper`` without any knowledge of what that program considers to be valid arguments. The string of arguments must be quoted as shown in the examples below. No filename arguments may be included. OCRmyPDF will assume it can append input and output filename of intermediate images to the ``--unpaper-args`` string.
+However, if you wish to use the more aggressive options in ``unpaper``,
+you may use ``--unpaper-args '...'`` to override the OCRmyPDF's defaults
+and forward other arguments to unpaper. This option will forward
+arguments to ``unpaper`` without any knowledge of what that program
+considers to be valid arguments. The string of arguments must be quoted
+as shown in the examples below. No filename arguments may be included.
+OCRmyPDF will assume it can append input and output filename of
+intermediate images to the ``--unpaper-args`` string.
 
-In this example, we tell ``unpaper`` to expect two pages of text on a sheet (image), such as occurs when two facing pages of a book are scanned. ``unpaper`` uses this information to deskew each independently and clean up the margins of both.
+In this example, we tell ``unpaper`` to expect two pages of text on a
+sheet (image), such as occurs when two facing pages of a book are
+scanned. ``unpaper`` uses this information to deskew each independently
+and clean up the margins of both.
 
 .. code-block:: bash
 
@@ -19,40 +37,71 @@ In this example, we tell ``unpaper`` to expect two pages of text on a sheet (ima
 
 .. warning::
 
-    Some ``unpaper`` features will reposition text within the image. ``--clean-final`` is recommended to avoid this issue.
+   Some ``unpaper`` features will reposition text within the image.
+   ``--clean-final`` is recommended to avoid this issue.
 
 .. warning::
 
-    Some ``unpaper`` features cause multiple input or output files to be consumed or produced. OCRmyPDF requires ``unpaper`` to consume one file and produce one file. An deviation from that condition will result in errors.
+   Some ``unpaper`` features cause multiple input or output files to be
+   consumed or produced. OCRmyPDF requires ``unpaper`` to consume one
+   file and produce one file. An deviation from that condition will
+   result in errors.
 
 .. note::
 
-    ``unpaper`` uses uncompressed PBM/PGM/PPM files for its intermediate files. For large images or documents, it can take a lot of temporary disk space.
+   ``unpaper`` uses uncompressed PBM/PGM/PPM files for its intermediate
+   files. For large images or documents, it can take a lot of temporary
+   disk space.
 
 Control of OCR options
-----------------------
+======================
 
-OCRmyPDF provides many features to control the behavior of the OCR engine, Tesseract.
+OCRmyPDF provides many features to control the behavior of the OCR
+engine, Tesseract.
 
 When OCR is skipped
-"""""""""""""""""""
+-------------------
 
-If a page in a PDF seems to have text, by default OCRmyPDF will exit without modifying the PDF. This is to ensure that PDFs that were previously OCRed or were "born digital" rather than scanned are not processed.
+If a page in a PDF seems to have text, by default OCRmyPDF will exit
+without modifying the PDF. This is to ensure that PDFs that were
+previously OCRed or were "born digital" rather than scanned are not
+processed.
 
-If ``--skip-text`` is issued, then no OCR will be performed on pages that already have text. The page will be copied to the output. This may be useful for documents that contain both "born digital" and scanned content, or to use OCRmyPDF to normalize and convert to PDF/A regardless of their contents.
+If ``--skip-text`` is issued, then no OCR will be performed on pages
+that already have text. The page will be copied to the output. This may
+be useful for documents that contain both "born digital" and scanned
+content, or to use OCRmyPDF to normalize and convert to PDF/A regardless
+of their contents.
 
-If ``--redo-ocr`` is issued, then a detailed text analysis is performed. Text is categorized as either visible or invisible. Invisible text (OCR) is stripped out. Then an image of each page is created with visible text masked out. The page image is sent for OCR, and any additional text is inserted as OCR. If a file contains a mix of text and bitmap images that contain text, OCRmyPDF will locate the additional text in images without disrupting the existing text.
+If ``--redo-ocr`` is issued, then a detailed text analysis is performed.
+Text is categorized as either visible or invisible. Invisible text (OCR)
+is stripped out. Then an image of each page is created with visible text
+masked out. The page image is sent for OCR, and any additional text is
+inserted as OCR. If a file contains a mix of text and bitmap images that
+contain text, OCRmyPDF will locate the additional text in images without
+disrupting the existing text.
 
-If ``--force-ocr`` is issued, then all pages will be rasterized to images, discarding any hidden OCR text, and rasterizing any printable text. This is useful for redoing OCR, for fixing OCR text with a damaged character map (text is selectable but not searchable), and destroying redacted information. Any forms and vector graphics will be rasterized as well.
+If ``--force-ocr`` is issued, then all pages will be rasterized to
+images, discarding any hidden OCR text, and rasterizing any printable
+text. This is useful for redoing OCR, for fixing OCR text with a damaged
+character map (text is selectable but not searchable), and destroying
+redacted information. Any forms and vector graphics will be rasterized
+as well.
 
 Time and image size limits
-""""""""""""""""""""""""""
+--------------------------
 
-By default, OCRmyPDF permits tesseract to run for three minutes (180 seconds) per page. This is usually more than enough time to find all text on a reasonably sized page with modern hardware.
+By default, OCRmyPDF permits tesseract to run for three minutes (180
+seconds) per page. This is usually more than enough time to find all
+text on a reasonably sized page with modern hardware.
 
-If a page is skipped, it will be inserted without OCR. If preprocessing was requested, the preprocessed image layer will be inserted.
+If a page is skipped, it will be inserted without OCR. If preprocessing
+was requested, the preprocessed image layer will be inserted.
 
-If you want to adjust the amount of time spent on OCR, change ``--tesseract-timeout``.  You can also automatically skip images that exceed a certain number of megapixels with ``--skip-big``. (A 300 DPI, 8.5×11" page is 8.4 megapixels.)
+If you want to adjust the amount of time spent on OCR, change
+``--tesseract-timeout``. You can also automatically skip images that
+exceed a certain number of megapixels with ``--skip-big``. (A 300 DPI,
+8.5×11" page is 8.4 megapixels.)
 
 .. code-block:: bash
 
@@ -60,21 +109,27 @@ If you want to adjust the amount of time spent on OCR, change ``--tesseract-time
     ocrmypdf --tesseract-timeout 300 --skip-big 50 bigfile.pdf output.pdf
 
 Overriding default tesseract
-""""""""""""""""""""""""""""
+----------------------------
 
 OCRmyPDF checks the system ``PATH`` for the ``tesseract`` binary.
 
-Some relevant environment variables that influence Tesseract's behavior include:
+Some relevant environment variables that influence Tesseract's behavior
+include:
 
 .. envvar:: TESSDATA_PREFIX
 
-    Overrides the path to Tesseract's data files. This can allow simultaneous installation of the "best" and "fast" training data sets. OCRmyPDF does not manage this environment variable.
+   Overrides the path to Tesseract's data files. This can allow
+   simultaneous installation of the "best" and "fast" training data
+   sets. OCRmyPDF does not manage this environment variable.
 
 .. envvar:: OMP_THREAD_LIMIT
 
-    Controls the number of threads Tesseract will use. OCRmyPDF will manage this environment if it is not already set. (Currently, it will set it to 1 because this gives the best results in testing.)
+   Controls the number of threads Tesseract will use. OCRmyPDF will
+   manage this environment if it is not already set. (Currently, it will
+   set it to 1 because this gives the best results in testing.)
 
-For example, if you have a development build of Tesseract don't wish to use the system installation, you can launch OCRmyPDF as follows:
+For example, if you have a development build of Tesseract don't wish to
+use the system installation, you can launch OCRmyPDF as follows:
 
 .. code-block:: bash
 
@@ -83,26 +138,34 @@ For example, if you have a development build of Tesseract don't wish to use the
         TESSDATA_PREFIX=/home/user/src/tesseract \
         ocrmypdf input.pdf output.pdf
 
-In this example ``TESSDATA_PREFIX`` is required to redirect Tesseract to an alternate folder for its "tessdata" files.
+In this example ``TESSDATA_PREFIX`` is required to redirect Tesseract to
+an alternate folder for its "tessdata" files.
 
 Overriding other support programs
-"""""""""""""""""""""""""""""""""
+---------------------------------
 
 In addition to tesseract, OCRmyPDF uses the following external binaries:
 
-* ``gs`` (Ghostscript)
-* ``unpaper``
-* ``qpdf``
-
-In each case OCRmyPDF will search the ``PATH`` environment variable to locate the binaries.
+-  ``gs`` (Ghostscript)
+-  ``unpaper``
+-  ``pngquant``
+-  ``jbig2``
 
+In each case OCRmyPDF will search the ``PATH`` environment variable to
+locate the binaries.
 
 Changing tesseract configuration variables
-""""""""""""""""""""""""""""""""""""""""""
+------------------------------------------
 
-You can override tesseract's default `control parameters <https://github.com/tesseract-ocr/tesseract/wiki/ControlParams>`_ with a configuration file.
+You can override tesseract's default `control
+parameters <https://github.com/tesseract-ocr/tesseract/wiki/ControlParams>`__
+with a configuration file.
 
-As an example, this configuration will disable Tesseract's dictionary for current language. Normally the dictionary is helpful for interpolating words that are unclear, but it may interfere with OCR if the document does not contain many words (for example, a list of part numbers).
+As an example, this configuration will disable Tesseract's dictionary
+for current language. Normally the dictionary is helpful for
+interpolating words that are unclear, but it may interfere with OCR if
+the document does not contain many words (for example, a list of part
+numbers).
 
 Create a file named "no-dict.cfg" with these contents:
 
@@ -120,11 +183,11 @@ then run ocrmypdf as follows (along with any other desired arguments):
 
 .. warning::
 
-    Some combinations of control parameters will break Tesseract or break assumptions that OCRmyPDF makes about Tesseract's output.
-
+   Some combinations of control parameters will break Tesseract or break
+   assumptions that OCRmyPDF makes about Tesseract's output.
 
 Changing the PDF renderer
--------------------------
+=========================
 
 rasterizing
   Converting a PDF to an image for display.
@@ -132,42 +195,63 @@ rasterizing
 rendering
   Creating a new PDF from other data (such as an existing PDF).
 
-
-OCRmyPDF has these PDF renderers: ``sandwich`` and ``hocr``. The renderer may be selected using ``--pdf-renderer``. The default is ``auto`` which lets OCRmyPDF select the renderer to use. Currently, ``auto`` always selects ``sandwich``.
+OCRmyPDF has these PDF renderers: ``sandwich`` and ``hocr``. The
+renderer may be selected using ``--pdf-renderer``. The default is
+``auto`` which lets OCRmyPDF select the renderer to use. Currently,
+``auto`` always selects ``sandwich``.
 
 The ``sandwich`` renderer
-"""""""""""""""""""""""""
+-------------------------
 
-The ``sandwich`` renderer uses Tesseract's new text-only PDF feature, which produces a PDF page that lays out the OCR in invisible text. This page is then "sandwiched" onto the original PDF page, allowing lossless application of OCR even to PDF pages that contain other vector objects.
+The ``sandwich`` renderer uses Tesseract's new text-only PDF feature,
+which produces a PDF page that lays out the OCR in invisible text. This
+page is then "sandwiched" onto the original PDF page, allowing lossless
+application of OCR even to PDF pages that contain other vector objects.
 
-Currently this is the best renderer for most uses, however it is implemented in Tesseract so OCRmyPDF cannot influence it. Currently some problematic PDF viewers like Mozilla PDF.js and macOS Preview have problems with segmenting its text output, and mightrunseveralwordstogether.
+Currently this is the best renderer for most uses, however it is
+implemented in Tesseract so OCRmyPDF cannot influence it. Currently some
+problematic PDF viewers like Mozilla PDF.js and macOS Preview have
+problems with segmenting its text output, and
+mightrunseveralwordstogether.
 
-When image preprocessing features like ``--deskew`` are used, the original PDF will be rendered as a full page and the OCR layer will be placed on top.
+When image preprocessing features like ``--deskew`` are used, the
+original PDF will be rendered as a full page and the OCR layer will be
+placed on top.
 
 The ``hocr`` renderer
-"""""""""""""""""""""
+---------------------
 
-The ``hocr`` renderer works with older versions of Tesseract. The image layer is copied from the original PDF page if possible, avoiding potentially lossy transcoding or loss of other PDF information. If preprocessing is specified, then the image layer is a new PDF.
+The ``hocr`` renderer works with older versions of Tesseract. The image
+layer is copied from the original PDF page if possible, avoiding
+potentially lossy transcoding or loss of other PDF information. If
+preprocessing is specified, then the image layer is a new PDF.
 
-Unlike ``sandwich`` this renderer is implemented within OCRmyPDF; anyone looking to customize how OCR is presented should look here. A major disadvantage of this renderer is it not capable of correctly handling text outside the Latin alphabet. Pull requests to improve the situation are welcome.
+Unlike ``sandwich`` this renderer is implemented within OCRmyPDF; anyone
+looking to customize how OCR is presented should look here. A major
+disadvantage of this renderer is it not capable of correctly handling
+text outside the Latin alphabet. Pull requests to improve the situation
+are welcome.
 
-Currently, this renderer has the best compatibility with Mozilla's PDF.js viewer.
+Currently, this renderer has the best compatibility with Mozilla's
+PDF.js viewer.
 
 This works in all versions of Tesseract.
 
 The ``tesseract`` renderer
-""""""""""""""""""""""""""
+--------------------------
 
-The ``tesseract`` renderer was removed. OCRmyPDF's new approach to text layer grafting makes it functionally equivalent to ``sandwich``.
+The ``tesseract`` renderer was removed. OCRmyPDF's new approach to text
+layer grafting makes it functionally equivalent to ``sandwich``.
 
 Return code policy
-------------------
+==================
 
-OCRmyPDF writes all messages to ``stderr``.  ``stdout`` is reserved for piping
-output files.  ``stdin`` is reserved for piping input files.
+OCRmyPDF writes all messages to ``stderr``. ``stdout`` is reserved for
+piping output files. ``stdin`` is reserved for piping input files.
 
-The return codes generated by the OCRmyPDF are considered part of the stable
-user interface.  They may be imported from ``ocrmypdf.exceptions``.
+The return codes generated by the OCRmyPDF are considered part of the
+stable user interface. They may be imported from
+``ocrmypdf.exceptions``.
 
 .. list-table:: Return codes
     :widths: 5 35 60
@@ -218,22 +302,44 @@ user interface.  They may be imported from ``ocrmypdf.exceptions``.
 
 
 Debugging the intermediate files
---------------------------------
+================================
 
-OCRmyPDF normally saves its intermediate results to a temporary folder and deletes this folder when it exits, whether it succeeded or failed.
+OCRmyPDF normally saves its intermediate results to a temporary folder
+and deletes this folder when it exits, whether it succeeded or failed.
 
-If the ``-k`` argument is issued on the command line, OCRmyPDF will keep the temporary folder and print the location, whether it succeeded or failed (provided the Python interpreter did not crash). An example message is:
+If the ``-k`` argument is issued on the command line, OCRmyPDF will keep
+the temporary folder and print the location, whether it succeeded or
+failed (provided the Python interpreter did not crash). An example
+message is:
 
 .. code-block:: none
 
-    Temporary working files saved at:
+    Temporary working files retained at:
     /tmp/com.github.ocrmypdf.u20wpz07
 
-The organization of this folder is an implementation detail and subject to change between releases. However the general organization is that working files on a per page basis have the page number as a prefix (starting with page 1), an infix indicates the processing stage, and a suffix indicates the file type. Some important files include:
+The organization of this folder is an implementation detail and subject
+to change between releases. However the general organization is that
+working files on a per page basis have the page number as a prefix
+(starting with page 1), an infix indicates the processing stage, and a
+suffix indicates the file type. Some important files include:
 
-* ``.page.png`` - what the input page looks like
-* ``.image`` - the image we will show the user if we are in a mode that changes the final appearance; may be in one of several image formats
-* ``.text.pdf`` - the OCR file; this will load as a blank page but should have visible text if checked with a tool like pdftotext or pdfminder.six
-* ``.ocr.png`` - the file that is sent to Tesseract for OCR; depending on arguments this may differ from the presentation image
-* ``layers.rendered.pdf`` - the composite PDF, before metadata repair and optimization
-* ``images/*`` - images extracted during the optimization process; here the prefix indicates a PDF object ID not a page number
+-  ``_rasterize.png`` - what the input page looks like
+-  ``_ocr.png`` - the file that is sent to Tesseract for OCR; depending
+   on arguments this may differ from the presentation image
+-  ``_pp_deskew.png`` - the image, after deskewing
+-  ``_pp_clean.png`` - the image, after cleaning with unpaper
+-  ``_ocr_tess.pdf`` - the OCR file; appears as a blank page with invisible
+   text embedded
+-  ``_ocr_tess.txt`` - the OCR text (not necessarily all text on the page,
+   if the page is mixed format)
+-  ``fix_docinfo.pdf`` - a temporary file created to fix the PDF DocumentInfo
+   data structure
+-  ``graft_layers.pdf`` - the rendered PDF with OCR layers grafted on
+-  ``pdfa.pdf`` - ``graft_layers.pdf`` after conversion to PDF/A
+-  ``pdfa.ps`` - a PostScript file used by Ghostscript for PDF/A conversion
+-  ``optimize.pdf`` - the PDF generated before optimization
+-  ``optimize.out.pdf`` - the PDF generated by optimization
+-  ``origin`` - the input file
+-  ``origin.pdf`` - the input file or the input image converted to PDF
+-  ``images/*`` - images extracted during the optimization process; here
+   the prefix indicates a PDF object ID not a page number

docs/api.rst

@@ -0,0 +1,112 @@
+======================
+Using the OCRmyPDF API
+======================
+
+OCRmyPDF originated as a command line program and continues to have this
+legacy, but parts of it can be imported and used in other Python
+applications.
+
+Some applications may want to consider running ocrmypdf from a
+subprocess call anyway, as this provides isolation of its activities.
+
+Example
+=======
+
+OCRmyPDF one high-level function to run its main engine from an
+application. The parameters are symmetric to the command line arguments
+and largely have the same functions.
+
+.. code-block:: python
+
+    import ocrmypdf
+
+    ocrmypdf.ocr('input.pdf', 'output.pdf', deskew=True)
+
+With a few exceptions, all of the command line arguments are available
+and may be passed as equivalent keywords.
+
+A few differences are that ``verbose`` and ``quiet`` are not available.
+Instead, output should be managed by configuring logging.
+
+Parent process requirements
+---------------------------
+
+The :func:`ocrmypdf.ocr` function runs OCRmyPDF similar to command line
+execution. To do this, it will:
+
+- create a monitoring thread
+- create worker processes (forking itself)
+- manage the signal flags of worker processes
+- execute other subprocesses (forking and executing other programs)
+
+The Python process that calls ``ocrmypdf.ocr()`` must be sufficiently
+privileged to perform these actions. If it is not, ``ocrmypdf()`` will
+fail.
+
+There is no currently no option to manage how jobs are scheduled other
+than the argument ``jobs=`` which will limit the number of worker
+processes.
+
+Forking a child process to call ``ocrmypdf.ocr()`` is suggested. That
+way your application will survive and remain interactive even if
+OCRmyPDF does not.
+
+Programs that call ``ocrmypdf.ocr()`` should also install a SIGBUS signal
+handler (except on Windows), to raise an exception if access to a memory
+mapped file fails. OCRmyPDF may use memory mapping.
+
+.. warning::
+
+    On Windows, the script that calls ``ocrmypdf.ocr()`` must be protected
+    by an "ifmain" guard (``if __name__ == '__main__'``) or you must use
+    ``ocrmypdf.ocr(...use_threads=True)``. If you do not take at least one
+    of these steps, Windows process semantics will prevent OCRmyPDF from working
+    correctly.
+
+Logging
+-------
+
+OCRmyPDF will log under loggers named ``ocrmypdf``. In addition, it
+imports ``pdfminer`` and ``PIL``, both of which post log messages under
+those logging namespaces.
+
+You can configure the logging as desired for your application or call
+:func:`ocrmypdf.configure_logging` to configure logging the same way
+OCRmyPDF itself does. The command line parameters such as ``--quiet``
+and ``--verbose`` have no equivalents in the API; you must use the
+provided configuration function or do configuration in a way that suits
+your use case.
+
+Progress monitoring
+-------------------
+
+OCRmyPDF uses the ``tqdm`` package to implement its progress bars.
+:func:`ocrmypdf.configure_logging` will set up logging output to
+``sys.stderr`` in a way that is compatible with the display of the
+progress bar. Use ``ocrmypdf.ocr(...progress_bar=False)`` to disable
+the progress bar.
+
+Exceptions
+----------
+
+OCRmyPDF may throw standard Python exceptions, ``ocrmypdf.exceptions.*``
+exceptions, some exceptions related to multiprocessing, and
+``KeyboardInterrupt``. The parent process should provide an exception
+handler. OCRmyPDF will clean up its temporary files and worker processes
+automatically when an exception occurs.
+
+Programs that call OCRmyPDF should consider trapping KeyboardInterrupt
+so that they allow OCR to terminate with the whole program terminating.
+
+When OCRmyPDF succeeds conditionally, it returns an integer exit code.
+
+Reference
+---------
+
+.. autofunction:: ocrmypdf.ocr
+
+.. autoclass:: ocrmypdf.Verbosity
+    :members:
+    :undoc-members:
+
+.. autofunction:: ocrmypdf.configure_logging

docs/apiref.rst

@@ -0,0 +1,43 @@
+=============
+API Reference
+=============
+
+This page summarizes the rest of the public API. Generally speaking this
+should mainly of interest to plugin developers.
+
+ocrmypdf.exceptions
+===================
+
+.. automodule:: ocrmypdf.exceptions
+    :members:
+    :undoc-members:
+
+ocrmypdf.helpers
+================
+
+.. automodule:: ocrmypdf.helpers
+    :members:
+
+ocrmypdf.hocrtransform
+======================
+
+.. automodule:: ocrmypdf.hocrtransform
+    :members:
+
+ocrmypdf.pdfa
+=============
+
+.. automodule:: ocrmypdf.pdfa
+    :members:
+
+ocrmypdf.quality
+================
+
+.. automodule:: ocrmypdf.quality
+    :members:
+
+ocrmypdf.subprocess
+===================
+
+.. automodule:: ocrmypdf.subprocess
+    :members:

docs/batch.rst

@@ -1,212 +1,224 @@
+================
 Batch processing
 ================
 
-This article provides information about running OCRmyPDF on multiple files or configuring it as a service triggered by file system events.
+This article provides information about running OCRmyPDF on multiple
+files or configuring it as a service triggered by file system events.
 
 Batch jobs
-----------
+==========
 
-Consider using the excellent `GNU Parallel <https://www.gnu.org/software/parallel/>`_ to apply OCRmyPDF to multiple files at once.
+Consider using the excellent `GNU
+Parallel <https://www.gnu.org/software/parallel/>`__ to apply OCRmyPDF
+to multiple files at once.
 
-Both ``parallel`` and ``ocrmypdf`` will try to use all available processors. To maximize parallelism without overloading your system with processes, consider using ``parallel -j 2`` to limit parallel to running two jobs at once.
+Both ``parallel`` and ``ocrmypdf`` will try to use all available
+processors. To maximize parallelism without overloading your system with
+processes, consider using ``parallel -j 2`` to limit parallel to running
+two jobs at once.
 
-This command will run all ocrmypdf all files named ``*.pdf`` in the current directory and write them to the previous created ``output/`` folder. It will not search subdirectories.
+This command will run all ocrmypdf all files named ``*.pdf`` in the
+current directory and write them to the previous created ``output/``
+folder. It will not search subdirectories.
 
-The ``--tag`` argument tells parallel to print the filename as a prefix whenever a message is printed, so that one can trace any errors to the file that produced them.
+The ``--tag`` argument tells parallel to print the filename as a prefix
+whenever a message is printed, so that one can trace any errors to the
+file that produced them.
 
 .. code-block:: bash
 
-	parallel --tag -j 2 ocrmypdf '{}' 'output/{}' ::: *.pdf
+   parallel --tag -j 2 ocrmypdf '{}' 'output/{}' ::: *.pdf
 
-OCRmyPDF automatically repairs PDFs before parsing and gathering information from them.
+OCRmyPDF automatically repairs PDFs before parsing and gathering
+information from them.
 
 Directory trees
----------------
+===============
 
-This will walk through a directory tree and run OCR on all files in place, printing the output in a way that makes
+This will walk through a directory tree and run OCR on all files in
+place, printing the output in a way that makes
 
 .. code-block:: bash
 
-	find . --printf '%p' -name '*.pdf' -exec ocrmypdf '{}' '{}' \;
+   find . -printf '%p' -name '*.pdf' -exec ocrmypdf '{}' '{}' \;
 
-This only runs one ``ocrmypdf`` process at a time. This variation uses ``find`` to create a directory list and ``parallel`` to parallelize runs of ``ocrmypdf``, again updating files in place.
+Alternatively, with a docker container (mounts a volume to the container
+where the PDFs are stored):
 
 .. code-block:: bash
 
-	find . -name '*.pdf' | parallel --tag -j 2 ocrmypdf '{}' '{}'
+   find . -printf '%p' -name '*.pdf' -exec docker run --rm -v <host dir>:<container dir> jbarlow83/ocrmypdf '<container dir>/{}' '<container dir>/{}' \;
 
+This only runs one ``ocrmypdf`` process at a time. This variation uses
+``find`` to create a directory list and ``parallel`` to parallelize runs
+of ``ocrmypdf``, again updating files in place.
+
+.. code-block:: bash
+
+   find . -name '*.pdf' | parallel --tag -j 2 ocrmypdf '{}' '{}'
+
+In a Windows batch file, use
+
+.. code-block:: bat
+
+   for /r %%f in (*.pdf) do ocrmypdf %%f %%f
 
 Sample script
-"""""""""""""
+-------------
 
-This user contributed script also provides an example of batch processing.
-
-.. code-block:: python
-
-	#!/usr/bin/env python3
-	# Walk through directory tree, replacing all files with OCR'd version
-	# Contributed by DeliciousPickle@github
-
-	import logging
-	import os
-	import subprocess
-	import sys
-
-	script_dir = os.path.dirname(os.path.realpath(__file__))
-	print(script_dir + '/ocr-tree.py: Start')
-
-	if len(sys.argv) > 1:
-	    start_dir = sys.argv[1]
-	else:
-	    start_dir = '.'
-
-	if len(sys.argv) > 2:
-	    log_file = sys.argv[2]
-	else:
-	    log_file = script_dir + '/ocr-tree.log'
-
-	logging.basicConfig(
-			level=logging.INFO, format='%(asctime)s %(message)s',
-			filename=log_file, filemode='w')
-
-	for dir_name, subdirs, file_list in os.walk(start_dir):
-	    logging.info('\n')
-	    logging.info(dir_name + '\n')
-	    os.chdir(dir_name)
-	    for filename in file_list:
-	        file_ext = os.path.splitext(filename)[1]
-	        if file_ext == '.pdf':
-	            full_path = dir_name + '/' + filename
-	            print(full_path)
-	            cmd = ["ocrmypdf",  "--deskew", filename, filename]
-	            logging.info(cmd)
-	            proc = subprocess.run(
-	            	cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-	            result = proc.stdout
-	            if proc.returncode == 6:
-	                print("Skipped document because it already contained text")
-	            elif proc.returncode == 0:
-	                print("OCR complete")
-	            logging.info(result)
-
-API
-"""
-
-OCRmyPDF is currently supported as a command line interface. This means that even if you are using OCRmyPDF in a Python script, you should run it in a subprocess rather importing the ocrmypdf package.
-
-The reason for this limitation is that the `ruffus <https://github.com/bunbun/ruffus/>`_ library that OCRmyPDF depends on is unfortunately not reentrant. OCRmyPDF works by defining each operation it does as a ruffus task that takes one or more files as input and generates one or more files as output. As such ruffus is fairly fundamental.
-
-(If you find individual functions implemented in OCRmyPDF useful (such as ``ocrmypdf.pdfinfo``), you can use these if you wish to.)
+This user contributed script also provides an example of batch
+processing.
 
+.. literalinclude:: ../misc/batch.py
+    :caption: misc/batch.py
 
 Synology DiskStations
-"""""""""""""""""""""
-
-Synology DiskStations (Network Attached Storage devices) can run the Docker image of OCRmyPDF if the Synology `Docker package <https://www.synology.com/en-global/dsm/packages/Docker>`_ is installed. Attached is a script to address particular quirks of using OCRmyPDF on one of these devices.
-
-This is only possible for x86-based Synology products. Some Synology products use ARM or Power processors and do not support Docker. Further adjustments might be needed to deal with the Synology's relatively limited CPU and RAM.
-
-.. code-block:: python
-
-	#!/bin/env python3
-	# Contributed by github.com/Enantiomerie
-
-	# script needs 2 arguments
-	# 1. source dir with *.pdf - default is location of script
-	# 2. move dir where *.pdf and *_OCR.pdf are moved to
-
-	import logging
-	import os
-	import subprocess
-	import sys
-	import time
-	import shutil
-
-	script_dir = os.path.dirname(os.path.realpath(__file__))
-	timestamp = time.strftime("%Y-%m-%d-%H%M_")
-	log_file = script_dir + '/' + timestamp + 'ocrmypdf.log'
-	logging.basicConfig(level=logging.INFO, format='%(asctime)s %(message)s', filename=log_file, filemode='w')
-
-	if len(sys.argv) > 1:
-	    start_dir = sys.argv[1]
-	else:
-	    start_dir = '.'
-
-	for dir_name, subdirs, file_list in os.walk(start_dir):
-	    logging.info('\n')
-	    logging.info(dir_name + '\n')
-	    os.chdir(dir_name)
-	    for filename in file_list:
-	        file_ext = os.path.splitext(filename)[1]
-	        if file_ext == '.pdf':
-	            full_path = dir_name + '/' + filename
-	            file_noext = os.path.splitext(filename)[0]
-	            timestamp_OCR = time.strftime("%Y-%m-%d-%H%M_OCR_")
-	            filename_OCR = timestamp_OCR + file_noext + '.pdf'
-	            docker_mount = dir_name + ':/home/docker'
-	# create string for pdf processing
-	# diskstation needs a user:group docker:docker. find uid:gid of your diskstation docker:docker with id docker.
-	# use this uid:gid in -u flag
-	# rw rights for docker:docker at source dir are also necessary
-	# the script is processed as root user via chron
-	            cmd = ['docker', 'run', '--rm', '-v', docker_mount, '-u=1030:65538', 'jbarlow83/ocrmypdf', , '--deskew' , filename, filename_OCR]
-	            logging.info(cmd)
-	            proc = subprocess.run(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-	            result = proc.stdout.read()
-	            logging.info(result)
-	            full_path_OCR = dir_name + '/' + filename_OCR
-	            os.chmod(full_path_OCR, 0o666)
-	            os.chmod(full_path, 0o666)
-	            full_path_OCR_archive = sys.argv[2]
-	            full_path_archive = sys.argv[2] + '/no_ocr'
-	            shutil.move(full_path_OCR,full_path_OCR_archive)
-	            shutil.move(full_path, full_path_archive)
-	logging.info('Finished.\n')
-
-
-
-Huge batch jobs
-"""""""""""""""
-
-If you have thousands of files to work with, contact the author. Consulting work related to OCRmyPDF helps fund this open source project and all inquiries are appreciated.
-
-
-Hot (watched) folders
 ---------------------
 
-To set up a "hot folder" that will trigger OCR for every file inserted, use a program like Python `watchdog <https://pypi.python.org/pypi/watchdog>`_ (supports all major OS).
+Synology DiskStations (Network Attached Storage devices) can run the
+Docker image of OCRmyPDF if the Synology `Docker
+package <https://www.synology.com/en-global/dsm/packages/Docker>`__ is
+installed. Attached is a script to address particular quirks of using
+OCRmyPDF on one of these devices.
 
-One could then configure a scanner to automatically place scanned files in a hot folder, so that they will be queued for OCR and copied to the destination.
+This is only possible for x86-based Synology products. Some Synology
+products use ARM or Power processors and do not support Docker. Further
+adjustments might be needed to deal with the Synology's relatively
+limited CPU and RAM.
+
+.. literalinclude:: ../misc/synology.py
+    :caption: misc/synology.py - Sample script for Synology DiskStations
+
+Huge batch jobs
+---------------
+
+If you have thousands of files to work with, contact the author.
+Consulting work related to OCRmyPDF helps fund this open source project
+and all inquiries are appreciated.
+
+Hot (watched) folders
+=====================
+
+Watched folders with watcher.py
+-------------------------------
+
+OCRmyPDF has a folder watcher called watcher.py, which is currently included in source
+distributions but not part of the main program. It may be used natively or may run
+in a Docker container. Native instances tend to give better performance. watcher.py
+works on all platforms.
+
+Users may need to customize the script to meet their requirements.
 
 .. code-block:: bash
 
-	pip install watchdog
+    pip3 install -r requirements/watcher.txt
 
-watchdog installs the command line program ``watchmedo``, which can be told to run ``ocrmypdf`` on any .pdf added to the current directory (``.``) and place the result in the previously created ``out/`` folder.
+    env OCR_INPUT_DIRECTORY=/mnt/input-pdfs \
+        OCR_OUTPUT_DIRECTORY=/mnt/output-pdfs \
+        OCR_OUTPUT_DIRECTORY_YEAR_MONTH=1 \
+        python3 watcher.py
+
+.. csv-table:: watcher.py environment variables
+    :header: "Environment variable", "Description"
+    :widths: 50, 50
+
+    "OCR_INPUT_DIRECTORY", "Set input directory to monitor (recursive)"
+    "OCR_OUTPUT_DIRECTORY", "Set output directory (should not be under input)"
+    "OCR_ON_SUCCESS_DELETE", "This will delete the input file if the exit code is 0 (OK)"
+    "OCR_OUTPUT_DIRECTORY_YEAR_MONTH", "This will place files in the output in ``{output}/{year}/{month}/{filename}``"
+    "OCR_DESKEW", "Apply deskew to crooked input PDFs"
+    "OCR_JSON_SETTINGS", "A JSON string specifying any other arguments for ``ocrmypdf.ocr``, e.g. ``'OCR_JSON_SETTINGS={"rotate_pages": true}'``.
+    "OCR_POLL_NEW_FILE_SECONDS", "Polling interval"
+    "OCR_LOGLEVEL", "Level of log messages to report"
+
+One could configure a networked scanner or scanning computer to drop files in the
+watched folder.
+
+Watched folders with Docker
+---------------------------
+
+The watcher service is included in the OCRmyPDF Docker image. To run it:
 
 .. code-block:: bash
 
-	cd hot-folder
-	mkdir out
-	watchmedo shell-command \
-		--patterns="*.pdf" \
-		--ignore-directories \
-		--command='ocrmypdf "${watch_src_path}" "out/${watch_src_path}" ' \
-		.  # don't forget the final dot
+    docker run \
+        -v <path to files to convert>:/input \
+        -v <path to store results>:/output \
+        -e OCR_OUTPUT_DIRECTORY_YEAR_MONTH=1 \
+        -e OCR_ON_SUCCESS_DELETE=1 \
+        -e OCR_DESKEW=1 \
+        -e PYTHONUNBUFFERED=1 \
+        -it --entrypoint python3 \
+        jbarlow83/ocrmypdf \
+        watcher.py
 
-For more complex behavior you can write a Python script around to use the watchdog API.
+This service will watch for a file that matches ``/input/\*.pdf`` and will
+convert it to a OCRed PDF in ``/output/``. The parameters to this image are:
 
-On file servers, you could configure watchmedo as a system service so it will run all the time.
+.. csv-table:: watcher.py parameters for Docker
+    :header: "Parameter", "Description"
+    :widths: 50, 50
+
+    "``-v <path to files to convert>:/input``", "Files placed in this location will be OCRed"
+    "``-v <path to store results>:/output``", "This is where OCRed files will be stored"
+    "``-e OCR_OUTPUT_DIRECTORY_YEAR_MONTH=1``", "Define environment variable OCR_OUTPUT_DIRECTORY_YEAR_MONTH=1"
+    "``-e OCR_ON_SUCCESS_DELETE=1``", "Define environment variable"
+    "``-e OCR_DESKEW=1``", "Define environment variable"
+    "``-e PYTHONBUFFERED=1``", "This will force STDOUT to be unbuffered and allow you to see messages in docker logs"
+
+This service relies on polling to check for changes to the filesystem. It
+may not be suitable for some environments, such as filesystems shared on a
+slow network.
+
+A configuration manager such as Docker Compose could be used to ensure that the
+service is always available.
+
+.. literalinclude:: ../misc/docker-compose.example.yml
+    :language: yaml
+    :caption: misc/docker-compose.example.yml
 
 Caveats
-"""""""
+-------
 
-* ``watchmedo`` may not work properly on a networked file system, depending on the capabilities of the file system client and server.
-* This simple recipe does not filter for the type of file system event, so file copies, deletes and moves, and directory operations, will all be sent to ocrmypdf, producing errors in several cases. Disable your watched folder if you are doing anything other than copying files to it.
-* If the source and destination directory are the same, watchmedo may create an infinite loop.
-* On BSD, FreeBSD and older versions of macOS, you may need to increase the number of file descriptors to monitor more files, using ``ulimit -n 1024`` to watch a folder of up to 1024 files.
+-  ``watchmedo`` may not work properly on a networked file system,
+   depending on the capabilities of the file system client and server.
+-  This simple recipe does not filter for the type of file system event,
+   so file copies, deletes and moves, and directory operations, will all
+   be sent to ocrmypdf, producing errors in several cases. Disable your
+   watched folder if you are doing anything other than copying files to
+   it.
+-  If the source and destination directory are the same, watchmedo may
+   create an infinite loop.
+-  On BSD, FreeBSD and older versions of macOS, you may need to increase
+   the number of file descriptors to monitor more files, using
+   ``ulimit -n 1024`` to watch a folder of up to 1024 files.
 
 Alternatives
-""""""""""""
+------------
 
-* `Watchman <https://facebook.github.io/watchman/>`_ is a more powerful alternative to ``watchmedo``.
+-  On Linux, `systemd user services <https://wiki.archlinux.org/index.php/Systemd/User>`__
+   can be configured to automatically perform OCR on a collection of files.
+
+-  `Watchman <https://facebook.github.io/watchman/>`__ is a more
+   powerful alternative to ``watchmedo``.
+
+AWS Lambda is not viable
+------------------------
+
+AWS Lambda and its equivalents have low limits on execution time and payload
+size, relative to OCRmyPDF's needs. As of this writing, the request/response
+payload for AWS Lambda was 6 MB, which means many PDFs will not fit.
+
+macOS Automator
+===============
+
+You can use the Automator app with macOS, to create a Workflow or Quick
+Action. Use a *Run Shell Script* action in your workflow. In the context
+of Automator, the ``PATH`` may be set differently your Terminal's
+``PATH``; you may need to explicitly set the PATH to include
+``ocrmypdf``. The following example may serve as a starting point:
+
+.. figure:: images/macos-workflow.png
+    :alt: Example macOS Automator workflow
+
+You may customize the command sent to ocrmypdf.

docs/conf.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-# -*- coding: utf-8 -*-
 #
 # ocrmypdf documentation build configuration file, created by
 # sphinx-quickstart on Sun Sep  4 14:29:43 2016.
@@ -21,6 +20,8 @@
 # import sys
 # sys.path.insert(0, os.path.abspath('.'))
 
+"""isort:skip_file"""
+
 # -- General configuration ------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
@@ -30,9 +31,9 @@
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = [
-    # 'sphinx.ext.mathjax',
-]
+extensions = ['sphinx.ext.napoleon']
+
+napoleon_use_rtype = False
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -53,7 +54,7 @@ master_doc = 'index'
 # General information about the project.
 project = 'ocrmypdf'
 copyright = (
-    '2019, James R. Barlow. Licensed under Creative Commons Attribution-ShareAlike 4.0.'
+    '2020, James R. Barlow. Licensed under Creative Commons Attribution-ShareAlike 4.0.'
 )
 author = 'James R. Barlow'
 
@@ -92,6 +93,7 @@ from pkg_resources import get_distribution, DistributionNotFound
 release = get_distribution('ocrmypdf').version
 version = '.'.join(release.split('.')[:2])
 
+
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
 #
@@ -176,7 +178,7 @@ html_theme_options = {'display_version': False}
 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
 #
-# html_logo = None
+# html_logo = "images/logo.svg"  # looks bad
 
 # The name of an image file (relative to this directory) to use as a favicon of
 # the docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32

docs/contributing.rst

@@ -0,0 +1,57 @@
+=======================
+Contributing guidelines
+=======================
+
+Contributions are welcome!
+
+Big changes
+===========
+
+Please open a new issue to discuss or propose a major change. Not only is it fun
+to discuss big ideas, but we might save each other's time too. Perhaps some of the
+work you're contemplating is already half-done in a development branch.
+
+Code style
+==========
+
+We use PEP8, ``black`` for code formatting and ``isort`` for import sorting. The
+settings for these programs are in ``pyproject.toml`` and ``setup.cfg``. Pull
+requests should follow the style guide. One difference we use from "black" style
+is that strings shown to the user are always in double quotes (``"``) and strings
+for internal uses are in single quotes (``'``).
+
+Tests
+=====
+
+New features should come with tests that confirm their correctness.
+
+New Python dependencies
+=======================
+
+If you are proposing a change that will require a new Python dependency, we
+prefer dependencies that are already packaged by Debian or Red Hat. This makes
+life much easier for our downstream package maintainers.
+
+Python dependencies must also be GPLv3 compatible.
+
+New non-Python dependencies
+===========================
+
+OCRmyPDF uses several external programs (Tesseract, Ghostscript and others) for
+its functionality. In general we prefer to avoid adding new external programs.
+
+Style guide: Is it OCRmyPDF or ocrmypdf?
+========================================
+
+The program/project is OCRmyPDF and the name of the executable or library is ocrmypdf.
+
+Known ports/packagers
+=====================
+
+OCRmyPDF has been ported to many platforms already. If you are interesting in
+porting to a new platform, check with
+`Repology <https://repology.org/projects/?search=ocrmypdf>`__ to see the status
+of that platform.
+
+Packager maintainers, please ensure that the command line completion scripts in
+``misc/`` are installed.

docs/cookbook.rst

@@ -1,11 +1,12 @@
+========
 Cookbook
 ========
 
 Basic examples
---------------
+==============
 
 Help!
-^^^^^
+-----
 
 ocrmypdf has built-in help.
 
@@ -13,30 +14,29 @@ ocrmypdf has built-in help.
 
     ocrmypdf --help
 
-
 Add an OCR layer and convert to PDF/A
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+-------------------------------------
 
 .. code-block:: bash
 
     ocrmypdf input.pdf output.pdf
 
 Add an OCR layer and output a standard PDF
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+------------------------------------------
 
 .. code-block:: bash
 
     ocrmypdf --output-type pdf input.pdf output.pdf
 
 Create a PDF/A with all color and grayscale images converted to JPEG
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+--------------------------------------------------------------------
 
 .. code-block:: bash
 
     ocrmypdf --output-type pdfa --pdfa-image-compression jpeg input.pdf output.pdf
 
 Modify a file in place
-^^^^^^^^^^^^^^^^^^^^^^
+----------------------
 
 The file will only be overwritten if OCRmyPDF is successful.
 
@@ -45,48 +45,74 @@ The file will only be overwritten if OCRmyPDF is successful.
     ocrmypdf myfile.pdf myfile.pdf
 
 Correct page rotation
-^^^^^^^^^^^^^^^^^^^^^
+---------------------
 
-OCR will attempt to automatic correct the rotation of each page. This can help fix a scanning job that contains a mix of landscape and portrait pages.
+OCR will attempt to automatic correct the rotation of each page. This
+can help fix a scanning job that contains a mix of landscape and
+portrait pages.
 
 .. code-block:: bash
 
     ocrmypdf --rotate-pages myfile.pdf myfile.pdf
 
-You can increase (decrease) the parameter ``--rotate-pages-threshold`` to make page rotation more (less) aggressive.
+You can increase (decrease) the parameter ``--rotate-pages-threshold``
+to make page rotation more (less) aggressive. The threshold number is the ratio
+of how confidence the OCR engine is that the document image should be changed,
+compared to kept the same. A value of ``15.0`` is the default, and is fairly
+conservative. A value of ``2.0`` will produce more rotations, and more false
+positives.
 
-If the page is "just a little off horizontal", like a crooked picture, then you want ``--deskew``. ``--rotate-pages`` is for when the cardinal angle is wrong.
+If the page is "just a little off horizontal", like a crooked picture,
+then you want ``--deskew``. ``--rotate-pages`` is for when the cardinal
+angle is wrong.
 
 OCR languages other than English
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+--------------------------------
 
-OCRmyPDF assumes the document is in English unless told otherwise. OCR quality may be poor if the wrong language is used.
+OCRmyPDF assumes the document is in English unless told otherwise. OCR
+quality may be poor if the wrong language is used.
 
 .. code-block:: bash
 
     ocrmypdf -l fra LeParisien.pdf LeParisien.pdf
     ocrmypdf -l eng+fra Bilingual-English-French.pdf Bilingual-English-French.pdf
 
-Language packs must be installed for all languages specified. See :ref:`Installing additional language packs <lang-packs>`.
+Language packs must be installed for all languages specified. See
+:ref:`Installing additional language packs <lang-packs>`.
 
-Unfortunately, the Tesseract OCR engine has no ability to detect the language when it is unknown.
+Unfortunately, the Tesseract OCR engine has no ability to detect the
+language when it is unknown.
 
 Produce PDF and text file containing OCR text
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+---------------------------------------------
 
-This produces a file named "output.pdf" and a companion text file named "output.txt".
+This produces a file named "output.pdf" and a companion text file named
+"output.txt".
 
 .. code-block:: bash
 
     ocrmypdf --sidecar output.txt input.pdf output.pdf
 
+.. note::
+
+    The sidecar file contains the **OCR text** found by OCRmyPDF. If the document
+    contains pages that already have text, that text will not appear in the
+    sidecar. If the option ``--pages`` is used, only those pages on which OCR
+    was performed will be included in the sidecar. If certain pages were skipped
+    because of options like ``--skip-big`` or ``--tesseract-timeout``, those pages
+    will not be in the sidecar.
+
+    To extract all text from a PDF, whether generated from OCR or otherwise,
+    use a program like Poppler's ``pdftotext`` or ``pdfgrep``.
+
 OCR images, not PDFs
-^^^^^^^^^^^^^^^^^^^^
+--------------------
 
 Option: use Tesseract
-"""""""""""""""""""""
+~~~~~~~~~~~~~~~~~~~~~
 
-If you are starting with images, you can just use Tesseract directly to convert images to PDFs:
+If you are starting with images, you can just use Tesseract directly to
+convert images to PDFs:
 
 .. code-block:: bash
 
@@ -97,62 +123,88 @@ If you are starting with images, you can just use Tesseract directly to convert
     # When there are multiple images
     tesseract text-file-containing-list-of-image-filenames.txt output-prefix pdf
 
-Tesseract's PDF output is quite good – OCRmyPDF uses it internally, in some cases. However, OCRmyPDF has many features not available in Tesseract like image processing, metadata control, and PDF/A generation.
+Tesseract's PDF output is quite good – OCRmyPDF uses it internally, in
+some cases. However, OCRmyPDF has many features not available in
+Tesseract like image processing, metadata control, and PDF/A generation.
 
 Option: use img2pdf
-"""""""""""""""""""
+~~~~~~~~~~~~~~~~~~~
 
-You can also use a program like `img2pdf <https://gitlab.mister-muffin.de/josch/img2pdf>`_ to convert your images to PDFs, and then pipe the results to run ocrmypdf.  The ``-`` tells ocrmypdf to read standard input.
+You can also use a program like
+`img2pdf <https://gitlab.mister-muffin.de/josch/img2pdf>`__ to convert
+your images to PDFs, and then pipe the results to run ocrmypdf. The
+``-`` tells ocrmypdf to read standard input.
 
 .. code-block:: bash
 
     img2pdf my-images*.jpg | ocrmypdf - myfile.pdf
 
-``img2pdf`` is recommended because it does an excellent job at generating PDFs without transcoding images.
+``img2pdf`` is recommended because it does an excellent job at
+generating PDFs without transcoding images.
 
 Option: use OCRmyPDF (single images only)
-"""""""""""""""""""""""""""""""""""""""""
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-For convenience, OCRmyPDF can also convert single images to PDFs on its own. If the resolution (dots per inch, DPI) of an image is not set or is incorrect, it can be overridden with ``--image-dpi``. (As 1 inch is 2.54 cm, 1 dpi = 0.39 dpcm).
+For convenience, OCRmyPDF can also convert single images to PDFs on its
+own. If the resolution (dots per inch, DPI) of an image is not set or is
+incorrect, it can be overridden with ``--image-dpi``. (As 1 inch is 2.54
+cm, 1 dpi = 0.39 dpcm).
 
 .. code-block:: bash
 
     ocrmypdf --image-dpi 300 image.png myfile.pdf
 
-If you have multiple images, you must use ``img2pdf`` to convert the images to PDF.
+If you have multiple images, you must use ``img2pdf`` to convert the
+images to PDF.
 
 Not recommended
-"""""""""""""""
+~~~~~~~~~~~~~~~
 
-We caution against using ImageMagick or Ghostscript to convert images to PDF, since they may transcode images or produce downsampled images, sometimes without warning.
+We caution against using ImageMagick or Ghostscript to convert images to
+PDF, since they may transcode images or produce downsampled images,
+sometimes without warning.
 
 Image processing
-----------------
+================
 
-OCRmyPDF perform some image processing on each page of a PDF, if desired.  The same processing is applied to each page.  It is suggested that the user review files after image processing as these commands might remove desirable content, especially from poor quality scans.
+OCRmyPDF perform some image processing on each page of a PDF, if
+desired. The same processing is applied to each page. It is suggested
+that the user review files after image processing as these commands
+might remove desirable content, especially from poor quality scans.
 
-* ``--rotate-pages`` attempts to determine the correct orientation for each page and rotates the page if necessary.
-
-* ``--remove-background`` attempts to detect and remove a noisy background from grayscale or color images.  Monochrome images are ignored. This should not be used on documents that contain color photos as it may remove them.
-
-* ``--deskew`` will correct pages were scanned at a skewed angle by rotating them back into place.  Skew determination and correction is performed using `Postl's variance of line sums <http://www.leptonica.com/skew-measurement.html>`_ algorithm as implemented in `Leptonica <http://www.leptonica.com/index.html>`_.
-
-* ``--clean`` uses `unpaper <https://www.flameeyes.eu/projects/unpaper>`_ to clean up pages before OCR, but does not alter the final output.  This makes it less likely that OCR will try to find text in background noise.
-
-* ``--clean-final`` uses unpaper to clean up pages before OCR and inserts the page into the final output.  You will want to review each page to ensure that unpaper did not remove something important.
-
-* ``--mask-barcodes`` will suppress any barcodes detected in a page image. Barcodes are known to confuse Tesseract OCR and interfere with the recognition of text on the same baseline as a barcode. The output file will contain the unaltered image of the barcode.
+-  ``--rotate-pages`` attempts to determine the correct orientation for
+   each page and rotates the page if necessary.
+-  ``--remove-background`` attempts to detect and remove a noisy
+   background from grayscale or color images. Monochrome images are
+   ignored. This should not be used on documents that contain color
+   photos as it may remove them.
+-  ``--deskew`` will correct pages were scanned at a skewed angle by
+   rotating them back into place. Skew determination and correction is
+   performed using `Postl's variance of line
+   sums <http://www.leptonica.org/skew-measurement.html>`__ algorithm as
+   implemented in `Leptonica <http://www.leptonica.org/index.html>`__.
+-  ``--clean`` uses
+   `unpaper <https://www.flameeyes.eu/projects/unpaper>`__ to clean up
+   pages before OCR, but does not alter the final output. This makes it
+   less likely that OCR will try to find text in background noise.
+-  ``--clean-final`` uses unpaper to clean up pages before OCR and
+   inserts the page into the final output. You will want to review each
+   page to ensure that unpaper did not remove something important.
 
 .. note::
 
-    In many cases image processing will rasterize PDF pages as images, potentially losing quality.
+   In many cases image processing will rasterize PDF pages as images,
+   potentially losing quality.
 
 .. warning::
 
-    ``--clean-final`` and ``-remove-background`` may leave undesirable visual artifacts in some images where their algorithms have shortcomings. Files should be visually reviewed after using these options.
+   ``--clean-final`` and ``-remove-background`` may leave undesirable
+   visual artifacts in some images where their algorithms have
+   shortcomings. Files should be visually reviewed after using these
+   options.
 
 Example: OCR and correct document skew (crooked scan)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+-----------------------------------------------------
 
 Deskew:
 
@@ -160,55 +212,118 @@ Deskew:
 
     ocrmypdf --deskew input.pdf output.pdf
 
-Image processing commands can be combined. The order in which options are given does not matter. OCRmyPDF always applies the steps of the image processing pipeline in the same order (rotate, remove background, deskew, clean).
+Image processing commands can be combined. The order in which options
+are given does not matter. OCRmyPDF always applies the steps of the
+image processing pipeline in the same order (rotate, remove background,
+deskew, clean).
 
 .. code-block:: bash
 
     ocrmypdf --deskew --clean --rotate-pages input.pdf output.pdf
 
-
 Don't actually OCR my PDF
--------------------------
+=========================
 
-If you set ``--tesseract-timeout 0`` OCRmyPDF will apply its image processing without performing OCR, if all you want to is to apply image processing or PDF/A conversion.
+If you set ``--tesseract-timeout 0`` OCRmyPDF will apply its image
+processing without performing OCR, if all you want to is to apply image
+processing or PDF/A conversion.
 
 .. code-block:: bash
 
     ocrmypdf --tesseract-timeout=0 --remove-background input.pdf output.pdf
 
+Optimize images without performing OCR
+--------------------------------------
+
+You can also optimize all images without performing any OCR:
+
+.. code-block:: bash
+
+    ocrmypdf --tesseract-timeout=0 --optimize 3 --skip-text input.pdf output.pdf
+
+Perform OCR only certain pages
+------------------------------
+
+You can ask OCRmyPDF to only apply OCR to certain pages.
+
+.. code-block:: bash
+
+    ocrmypdf --pages 2,3,13-17 input.pdf output.pdf
+
+Hyphens denote a range of pages and commas separate page numbers. If you prefer
+to use spaces, quote all of the page numbers: ``--pages '2, 3, 5, 7'``.
+
+OCRmyPDF will warn if your list of page numbers contains duplicates or
+overlap pages. OCRmyPDF does not currently account for document page numbers,
+such as an introduction section of a book that uses Roman numerals. It simply
+counts the number of virtual pieces of paper since the start.
+
+Regardless of the argument to ``--pages``, OCRmyPDF will optimize all pages in
+the file and convert it to PDF/A, unless you disable those options. In this
+example, we want to OCR only the title and otherwise change the PDF as little
+as possible:
+
+.. code-block:: bash
+
+    ocrmypdf --pages 1 --output-type pdf --optimize 0 input.pdf output.pdf
 
 Redo existing OCR
------------------
+=================
 
-To redo OCR on a file OCRed with other OCR software or a previous version of OCRmyPDF and/or Tesseract, you may use the ``--redo-ocr`` argument. (Normally, OCRmyPDF will exit with an error if asked to modify a file with OCR.)
+To redo OCR on a file OCRed with other OCR software or a previous
+version of OCRmyPDF and/or Tesseract, you may use the ``--redo-ocr``
+argument. (Normally, OCRmyPDF will exit with an error if asked to modify
+a file with OCR.)
 
-This may be helpful for users who want to take advantage of accuracy improvements in Tesseract 4.0 for files they previously OCRed with an earlier version of Tesseract and OCRmyPDF.
+This may be helpful for users who want to take advantage of accuracy
+improvements in Tesseract 4.0 for files they previously OCRed with an
+earlier version of Tesseract and OCRmyPDF.
 
 .. code-block:: bash
 
     ocrmypdf --redo-ocr input.pdf output.pdf
 
-This method will replace OCR without rasterizing, reducing quality or removing vector content. If a file contains a mix of pure digital text and OCR, digital text will be ignored and OCR will be replaced. As such this mode is incompatible with image processing options, since they alter the appearance of the file.
+This method will replace OCR without rasterizing, reducing quality or
+removing vector content. If a file contains a mix of pure digital text
+and OCR, digital text will be ignored and OCR will be replaced. As such
+this mode is incompatible with image processing options, since they
+alter the appearance of the file.
 
-In some cases, existing OCR cannot be detected or replaced. Files produced by OCRmyPDF v2.2 or earlier, for example, are internally represented as having visible text with an opaque image drawn on top. This situation cannot be detected.
+In some cases, existing OCR cannot be detected or replaced. Files
+produced by OCRmyPDF v2.2 or earlier, for example, are internally
+represented as having visible text with an opaque image drawn on top.
+This situation cannot be detected.
 
-If ``--redo-ocr`` does not work, you can use ``--force-ocr``, which will force rasterization of all pages, potentially reducing quality or losing vector content.
+If ``--redo-ocr`` does not work, you can use ``--force-ocr``, which will
+force rasterization of all pages, potentially reducing quality or losing
+vector content.
 
 Improving OCR quality
----------------------
+=====================
 
-The `Image processing`_ features can improve OCR quality.
+The `Image processing <#image-processing>`__ features can improve OCR
+quality.
 
-Rotating pages and deskewing helps to ensure that the page orientation is correct before OCR begins. Removing the background and/or cleaning the page can also improve results. The ``--oversample DPI`` argument can be specified to resample images to higher resolution before attempting OCR; this can improve results as well.
+Rotating pages and deskewing helps to ensure that the page orientation
+is correct before OCR begins. Removing the background and/or cleaning
+the page can also improve results. The ``--oversample DPI`` argument can
+be specified to resample images to higher resolution before attempting
+OCR; this can improve results as well.
 
-OCR quality will suffer if the resolution of input images is not correct (since the range of pixel sizes that will be checked for possible fonts will also be incorrect).
+OCR quality will suffer if the resolution of input images is not correct
+(since the range of pixel sizes that will be checked for possible fonts
+will also be incorrect).
 
 PDF optimization
-----------------
+================
 
-By default OCRmyPDF will attempt to perform lossless optimizations on the images inside PDFs after OCR is complete. Optimization is performed even if no OCR text is found.
+By default OCRmyPDF will attempt to perform lossless optimizations on
+the images inside PDFs after OCR is complete. Optimization is performed
+even if no OCR text is found.
 
-The ``--optimize N`` (short form ``-O``) argument controls optimization, where ``N`` ranges from 0 to 3 inclusive, analogous to the optimization levels in the GCC compiler.
+The ``--optimize N`` (short form ``-O``) argument controls optimization,
+where ``N`` ranges from 0 to 3 inclusive, analogous to the optimization
+levels in the GCC compiler.
 
 .. list-table::
     :widths: auto
@@ -227,9 +342,15 @@ The ``--optimize N`` (short form ``-O``) argument controls optimization, where `
     *   - ``--optimize 3``
         - All of the above, and enables more aggressive optimizations and targets lower image quality.
 
-Optimization is improved when a JBIG2 encoder is available and when ``pngquant`` is installed. If either of these components are missing, then some types of images cannot be optimized.
+Optimization is improved when a JBIG2 encoder is available and when
+``pngquant`` is installed. If either of these components are missing,
+then some types of images cannot be optimized.
 
-The types of optimization available may expand over time. By default, OCRmyPDF compresses data streams inside PDFs, and will change inefficient compression modes to more modern versions. A program like ``qpdf`` can be used to change encodings, e.g. to inspect the internals fo a PDF.
+The types of optimization available may expand over time. By default,
+OCRmyPDF compresses data streams inside PDFs, and will change
+inefficient compression modes to more modern versions. A program like
+``qpdf`` can be used to change encodings, e.g. to inspect the internals
+fo a PDF.
 
 .. code-block:: bash
 

docs/docker.rst

@@ -1,155 +1,170 @@
+=====================
 OCRmyPDF Docker image
 =====================
 
-OCRmyPDF is also available in a Docker image that packages recent versions of all dependencies.
+OCRmyPDF is also available in a Docker image that packages recent
+versions of all dependencies.
 
-For users who already have Docker installed this may be an easy and convenient option. However, it is less performant than a system installation and may require Docker engine configuration.
+For users who already have Docker installed this may be an easy and
+convenient option. However, it is less performant than a system
+installation and may require Docker engine configuration.
 
-OCRmyPDF needs a generous amount of RAM, CPU cores, and temporary storage space.
+OCRmyPDF needs a generous amount of RAM, CPU cores, temporary storage
+space, whether running in a Docker container or on its own. It may be
+necessary to ensure the container is provisioned with additional
+resources.
 
 .. _docker-install:
 
 Installing the Docker image
----------------------------
+===========================
 
-If you have `Docker <https://docs.docker.com/>`_ installed on your system, you can install a Docker image of the latest release.
+If you have `Docker <https://docs.docker.com/>`__ installed on your
+system, you can install a Docker image of the latest release.
 
-The recommended OCRmyPDF Docker image is currently named ``ocrmypdf-alpine``:
+If you can run this command successfully, your system is ready to download and
+execute the image:
 
 .. code-block:: bash
 
-    docker pull jbarlow83/ocrmypdf-alpine
+   docker run hello-world
 
-Follow the Docker installation instructions for your platform.  If you can run this command successfully, your system is ready to download and execute the image:
+The recommended OCRmyPDF Docker image is currently named ``ocrmypdf``:
 
 .. code-block:: bash
 
-    docker run hello-world
+   docker pull jbarlow83/ocrmypdf
 
-OCRmyPDF will use all available CPU cores.  By default, the VirtualBox machine instance on Windows and macOS has only a single CPU core enabled. Use the VirtualBox Manager to determine the name of your Docker engine host, and then follow these optional steps to enable multiple CPUs:
+
+OCRmyPDF will use all available CPU cores. By default, the VirtualBox
+machine instance on Windows and macOS has only a single CPU core
+enabled. Use the VirtualBox Manager to determine the name of your Docker
+engine host, and then follow these optional steps to enable multiple
+CPUs:
 
 .. code-block:: bash
 
-    # Optional step for Mac OS X users
-    docker-machine stop "yourVM"
-    VBoxManage modifyvm "yourVM" --cpus 2  # or whatever number of core is desired
-    docker-machine start "yourVM"
-    eval $(docker-machine env "yourVM")
+   # Optional step for Mac OS X users
+   docker-machine stop "yourVM"
+   VBoxManage modifyvm "yourVM" --cpus 2  # or whatever number of core is desired
+   docker-machine start "yourVM"
+   eval $(docker-machine env "yourVM")
+
+See the Docker documentation for
+`adjusting memory and CPU on other platforms <https://docs.docker.com/config/containers/resource_constraints/>`__.
 
 Using the Docker image on the command line
-------------------------------------------
+==========================================
 
-**Unlike typical Docker containers**, in this mode we are using the OCRmyPDF Docker container is intended to be emphemeral – it runs for one OCR job and then terminates, just like a command line program. We are using Docker as a way of delivering an application, not a server.
+**Unlike typical Docker containers**, in this section the OCRmyPDF Docker
+container is emphemeral – it runs for one OCR job and terminates, just like a
+command line program. We are using Docker to deliver an application (as opposed
+to the more conventional case, where a Docker container runs as a server).
 
 To start a Docker container (instance of the image):
 
 .. code-block:: bash
 
-    docker tag jbarlow83/ocrmypdf-alpine ocrmypdf
-    docker run --rm ocrmypdf (... all other arguments here...)
+   docker tag jbarlow83/ocrmypdf ocrmypdf
+   docker run --rm -i ocrmypdf (... all other arguments here...) - -
 
-For convenience, create a shell alias to hide the Docker command:
+For convenience, create a shell alias to hide the Docker command. It is
+easier to send the input file as stdin and read the output from
+stdout – **this avoids the messy permission issues with Docker entirely**.
 
 .. code-block:: bash
 
-    alias ocrmypdf='docker run --rm -v "$(pwd):/home/docker" ocrmypdf'
-    ocrmypdf --version  # runs docker version
+   alias docker_ocrmypdf='docker run --rm -i ocrmypdf'
+   docker_ocrmypdf --version  # runs docker version
+   docker_ocrmypdf - - <input.pdf >output.pdf
 
-Or in the wonderful `fish shell <https://fishshell.com/>`_:
+Or in the wonderful `fish shell <https://fishshell.com/>`__:
 
 .. code-block:: fish
 
-    alias ocrmypdf 'docker run --rm ocrmypdf'
-    funcsave ocrmypdf
+   alias docker_ocrmypdf 'docker run --rm ocrmypdf'
+   funcsave docker_ocrmypdf
+
+Alternately, you could mount the local current working directory as a
+Docker volume:
+
+.. code-block:: bash
+
+   alias docker_ocrmypdf='docker run --rm  -i --user "$(id -u):$(id -g)" --workdir /data -v "$PWD:/data" ocrmypdf'
+   docker_ocrmypdf /data/input.pdf /data/output.pdf
 
 .. _docker-lang-packs:
 
 Adding languages to the Docker image
-------------------------------------
+====================================
 
-By default the Docker image includes English, German and Simplified Chinese, the most popular languages for OCRmyPDF users based on feedback. You may add other languages by creating a new Dockerfile based on the public one:
+By default the Docker image includes English, German, Simplified Chinese,
+French, Portuguese and Spanish, the most popular languages for OCRmyPDF
+users based on feedback. You may add other languages by creating a new
+Dockerfile based on the public one:
 
 .. code-block:: dockerfile
 
-    FROM jbarlow83/ocrmypdf-alpine
+   FROM jbarlow83/ocrmypdf
 
-    # Add French
-    RUN apk add tesseract-ocr-data-fra
+   # Add French
+   RUN apt install tesseract-ocr-fra
+
+You can also copy training data to ``/usr/share/tesseract-ocr/<tesseract version>/tessdata``.
 
 Executing the test suite
-------------------------
+========================
 
-The OCRmyPDF test suite is installed with image.  To run it:
+The OCRmyPDF test suite is installed with image. To run it:
 
 .. code-block:: bash
 
-    docker run --entrypoint python3 jbarlow83/ocrmypdf-alpine setup.py test
+   docker run --entrypoint python3  jbarlow83/ocrmypdf -m pytest
+
+Accessing the shell
+===================
+
+To use the bash shell in the Docker image:
+
+.. code-block:: bash
+
+   docker run -it --entrypoint bash  jbarlow83/ocrmypdf
 
 Using the OCRmyPDF web service wrapper
---------------------------------------
+======================================
 
-The OCRmyPDF Docker image includes an example, barebones HTTP web service. The webservice may be launched as follows:
+The OCRmyPDF Docker image includes an example, barebones HTTP web
+service. The webservice may be launched as follows:
 
 .. code-block:: bash
 
-    docker run --entrypoint python3 -p 5000:5000 jbarlow83/ocrmypdf-alpine webservice.py
+   docker run --entrypoint python3 -p 5000:5000  jbarlow83/ocrmypdf webservice.py
 
-Unlike command line usage this program will open a socket and wait for connections.
+This will configure the machine to listen on port 5000. On Linux machines
+this is port 5000 of localhost. On macOS or Windows machines running
+Docker, this is port 5000 of the virtual machine that runs your Docker
+images. You can find its IP address using the command ``docker-machine ip``.
+
+Unlike command line usage this program will open a socket and wait for
+connections.
 
 .. warning::
 
-    The OCRmyPDF web service wrapper is intended for demonstration or development. It provides no security, no authentication, no protection against denial of service attacks, and no load balancing. The default Flask WSGI server is used, which is intended for development only. The server is single-threaded and so can respond to only one client at a time. It cannot respond to clients while busy with OCR.
+   The OCRmyPDF web service wrapper is intended for demonstration or
+   development. It provides no security, no authentication, no
+   protection against denial of service attacks, and no load balancing.
+   The default Flask WSGI server is used, which is intended for
+   development only. The server is single-threaded and so can respond to
+   only one client at a time. While running OCR, it cannot respond to
+   any other clients.
 
-Clients must keep their open connection while waiting for OCR to complete. This may entail setting a long timeout; this interface is more useful for internal HTTP API calls.
+Clients must keep their open connection while waiting for OCR to
+complete. This may entail setting a long timeout; this interface is more
+useful for internal HTTP API calls.
 
-Unlike the rest of OCRmyPDF, this web service is licensed under the Affero GPLv3 (AGPLv3) since Ghostscript, a dependency of OCRmyPDF, is also licensed in this way.
+Unlike the rest of OCRmyPDF, this web service is licensed under the
+Affero GPLv3 (AGPLv3) since Ghostscript, a dependency of OCRmyPDF, is
+also licensed in this way.
 
-In addition to the above, please read our :ref:`general remarks on using OCRmyPDF as a service <ocr-service>`_.
-
-Legacy Ubuntu Docker images
----------------------------
-
-Previously OCRmyPDF was delivered in several Docker images for different purposes, based on Ubuntu.
-
-The Ubuntu-based images will be maintained for some time but should not be used for new deployments. They are as follows:
-
-.. list-table::
-    :widths: auto
-    :header-rows: 1
-
-    *   - Image name
-        - Download command
-        - Notes
-    *   - ocrmypdf
-        - ``docker pull jbarlow83/ocrmypdf``
-        - Latest ocrmypdf with Tesseract 4.0.0-beta1 on Ubuntu 18.04. Includes English, French, German, Spanish, Portugeuse and Simplified Chinese.
-    *   - ocrmypdf-polyglot
-        - ``docker pull jbarlow83/ocrmypdf-polyglot``
-        - As above, with all available language packs.
-    *   - ocrmypdf-webservice
-        - ``docker pull jbarlow83/ocrmypdf-webservice``
-        - All language packs, and a simple HTTP wrapper allowing OCRmyPDF to be used as a web service. Note that this component is licensed under AGPLv3.
-
-To execute the Ubuntu-based OCRmyPDF on a local file, you must `provide a writable volume to the Docker image <https://docs.docker.com/userguide/dockervolumes/>`_, and both the input and output file must be inside the writable volume. This limitation applies only to the legacy images.
-
-This example command uses the current working directory as the writable volume:
-
-.. code-block:: bash
-
-    docker run --rm -v "$(pwd):/home/docker" <other docker arguments>   ocrmypdf <your arguments to ocrmypdf>
-
-In this worked example, the current working directory contains an input file called ``test.pdf`` and the output will go to ``output.pdf``:
-
-.. code-block:: bash
-
-    docker run --rm -v "$(pwd):/home/docker"   ocrmypdf --skip-text test.pdf output.pdf
-
-.. note:: The working directory should be a writable local volume or Docker may not have permission to access it.
-
-Note that ``ocrmypdf`` has its own separate ``-v VERBOSITYLEVEL`` argument to control debug verbosity. All Docker arguments should before the ``ocrmypdf`` image name and all arguments to ``ocrmypdf`` should be listed after.
-
-In some environments the permissions associated with Docker can be complex to configure. The process that executes Docker may end up not having the permissions to write the specified file system. In that case one can stream the file into and out of the Docker process and avoid all permission hassles, using ``-`` as the input and output filename:
-
-.. code-block:: bash
-
-    docker run --rm -i   ocrmypdf <other arguments to ocrmypdf> - - <input.pdf >output.pdf
+In addition to the above, please read our
+:ref:`general remarks on using OCRmyPDF as a service <ocr-service>`.

docs/errors.rst

@@ -1,33 +1,53 @@
+=====================
 Common error messages
 =====================
 
 Page already has text
----------------------
+=====================
 
-.. code::
+.. code-block::
 
-	ERROR -    1: page already has text! – aborting (use --force-ocr to force OCR)
+   ERROR -    1: page already has text! – aborting (use --force-ocr to force OCR)
 
-You ran ocrmypdf on a file that already contains printable text or a hidden OCR text layer (it can't quite tell the difference). You probably don't want to do this, because the file is already searchable.
+You ran ocrmypdf on a file that already contains printable text or a
+hidden OCR text layer (it can't quite tell the difference). You probably
+don't want to do this, because the file is already searchable.
 
 As the error message suggests, your options are:
 
-- ``ocrmypdf --force-ocr`` to :ref:`rasterize <raster-vector>` all vector content and run OCR on the images. This is useful if a previous OCR program failed, or if the document contains a text watermark.
-
-- ``ocrmypdf --skip-text`` to skip OCR and other processing on any pages that contain text. Text pages will be copied into the output PDF without modification.
+-  ``ocrmypdf --force-ocr`` to :ref:`rasterize <raster-vector>` all
+   vector content and run OCR on the images. This is useful if a
+   previous OCR program failed, or if the document contains a text
+   watermark.
+-  ``ocrmypdf --skip-text`` to skip OCR and other processing on any
+   pages that contain text. Text pages will be copied into the output
+   PDF without modification.
+-  ``ocrmypdf --redo-ocr`` to scan the file for any existing OCR
+   (non-printing text), remove it, and do OCR again. This is one way
+   to take advantage of improvements in OCR accuracy. Printable vector
+   text is excluded from OCR, so this can be used on files that contain
+   a mix of digital and scanned files.
 
 
 Input file 'filename' is not a valid PDF
-----------------------------------------
+========================================
 
-OCRmyPDF passes files through qpdf, a program that fixes errors in PDFs, before it tries to work on them. In most cases this happens because the PDF is corrupt and
-truncated (incomplete file copying) and not much can be done.
+OCRmyPDF checks files with pikepdf, a library that in turn uses libqpdf to fixes
+errors in PDFs, before it tries to work on them. In most cases this happens
+because the PDF is corrupt and truncated (incomplete file copying) and not much
+can be done.
 
-You can try rewriting the file with Ghostscript or pdftk:
+You can try rewriting the file with Ghostscript:
 
-- ``gs -o output.pdf -dSAFER -sDEVICE=pdfwrite input.pdf``
+.. code-block:: bash
 
-- ``pdftk input.pdf cat output output.pdf``
+    gs -o output.pdf -dSAFER -sDEVICE=pdfwrite input.pdf
 
-Sometimes Acrobat can repair PDFs with its `Preflight tool <https://helpx.adobe.com/acrobat/using/correcting-problem-areas-preflight-tool.html>`_.
+``pdftk`` can also rewrite PDFs:
 
+.. code-block:: bash
+
+    pdftk input.pdf cat output output.pdf
+
+Sometimes Acrobat can repair PDFs with its `Preflight
+tool <https://helpx.adobe.com/acrobat/using/correcting-problem-areas-preflight-tool.html>`__.

docs/images/logo.svg

@@ -0,0 +1,75 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg width="100%" height="100%" viewBox="0 0 503 227" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve" xmlns:serif="http://www.serif.com/" style="fill-rule:evenodd;clip-rule:evenodd;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:1.5;">
+    <g id="svg" transform="matrix(0.965977,0,0,0.807602,0,0)">
+        <rect x="0" y="0" width="520" height="280" style="fill:white;"/>
+        <g transform="matrix(1.03522,0,0,1.23823,-69.7528,-83.422)">
+            <g transform="matrix(1,0,0,1,243.977,20.0703)">
+                <g id="Page">
+                    <g transform="matrix(0.961773,0,0,1.05962,6.19811,-3.01071)">
+                        <path d="M328.5,97.682C328.5,96.465 327.983,95.296 327.056,94.418C320.026,87.758 289.442,58.78 282.228,51.944C281.251,51.019 279.901,50.496 278.49,50.496C264.493,50.496 188.083,50.496 167.339,50.496C164.468,50.496 162.141,52.609 162.141,55.214C162.141,83.051 162.141,225.565 162.141,253.4C162.141,256.005 164.468,258.117 167.338,258.117C192.242,258.117 299.159,258.117 323.538,258.117C326.278,258.117 328.5,256.101 328.5,253.613C328.5,229.268 328.5,113.896 328.5,97.682Z" style="fill:rgb(253,253,253);stroke:rgb(51,51,51);stroke-width:3.95px;"/>
+                    </g>
+                    <g id="Dog-ear" serif:id="Dog ear" transform="matrix(1,0,0,1,-4,2)">
+                        <path d="M277.072,48.496L277.072,93.848C277.072,95.172 277.598,96.441 278.534,97.377C279.47,98.313 280.739,98.839 282.063,98.839C294.548,98.839 326.141,98.839 326.141,98.839" style="fill:rgb(245,245,245);stroke:rgb(51,51,51);stroke-width:4px;"/>
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+                <g transform="matrix(1,0,0,1,-29.6816,-0.395178)">
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+                    </g>
+                    <g transform="matrix(1.24571,0,0,1.35864,116.812,84.3924)">
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+                        </g>
+                        <g transform="matrix(64,0,0,64,79.7117,77.6203)">
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+                        </g>
+                        <g transform="matrix(64,0,0,64,123.424,77.6203)">
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+                        </g>
+                    </g>
+                </g>
+            </g>
+            <g transform="matrix(1,0,0,1.52217,67.3796,10.7507)">
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+            <g transform="matrix(0.967536,0,0,0.961535,5.90498,47.9703)">
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+                </g>
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+                </g>
+                <g transform="matrix(90.4804,0,0,90.4804,199.751,167.705)">
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+                </g>
+            </g>
+            <g transform="matrix(0.916882,0,0,1,121.475,-32.6535)">
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+                </g>
+                <g transform="matrix(86.953,0,0,86.953,228.906,241.878)">
+                    <path d="M0.156,0.023L0.179,-0.034L0.006,-0.467L0.14,-0.485L0.252,-0.191L0.358,-0.485L0.495,-0.485L0.278,0.064C0.263,0.103 0.236,0.137 0.197,0.165C0.158,0.193 0.118,0.212 0.075,0.222L0.029,0.115C0.052,0.105 0.077,0.093 0.104,0.079C0.13,0.064 0.147,0.046 0.156,0.023Z" style="fill:rgb(51,51,51);fill-rule:nonzero;"/>
+                </g>
+            </g>
+            <g id="Selectors" transform="matrix(0.965977,0,0,0.807602,67.3796,67.3718)">
+                <g id="Right-selector" serif:id="Right selector">
+                    <g transform="matrix(1.03522,0,0,1.23823,2.07044,0)">
+                        <path d="M185.806,161.156L185.806,67.132" style="fill:none;stroke:rgb(76,159,255);stroke-width:4px;stroke-linecap:butt;"/>
+                    </g>
+                    <g transform="matrix(1.03522,0,0,1.23823,161.788,169.469)">
+                        <circle cx="31.523" cy="34.314" r="10.021" style="fill:rgb(76,159,255);stroke:rgb(76,159,255);stroke-width:4px;stroke-linecap:butt;"/>
+                    </g>
+                </g>
+                <g id="Left-selector" serif:id="Left selector">
+                    <g transform="matrix(1.03522,0,0,1.23823,-170.092,0)">
+                        <path d="M185.806,161.156L185.806,67.132" style="fill:none;stroke:rgb(76,159,255);stroke-width:4px;stroke-linecap:butt;"/>
+                    </g>
+                    <g transform="matrix(1.03522,0,0,1.23823,-10.3742,28.2274)">
+                        <circle cx="31.523" cy="34.314" r="10.021" style="fill:rgb(76,159,255);stroke:rgb(76,159,255);stroke-width:4px;stroke-linecap:butt;"/>
+                    </g>
+                </g>
+            </g>
+        </g>
+    </g>
+</svg>

docs/index.rst

@@ -1,15 +1,12 @@
-.. ocrmypdf documentation master file, created by
-   sphinx-quickstart on Sun Sep  4 14:29:43 2016.
-   You can adapt this file completely to your liking, but it should at least
-   contain the root `toctree` directive.
-
 OCRmyPDF documentation
 ======================
 
-OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to
-be searched.
+OCRmyPDF adds an optical charcter recognition (OCR) text layer to scanned PDF
+files, allowing them to be searched.
 
-PDF is the best format for storing and exchanging scanned documents.  Unfortunately, PDFs can be difficult to modify. OCRmyPDF makes it easy to apply image processing and OCR to existing PDFs.
+PDF is the best format for storing and exchanging scanned documents.
+Unfortunately, PDFs can be difficult to modify. OCRmyPDF makes it easy to apply
+image processing and OCR to existing PDFs.
 
 .. toctree::
    :maxdepth: 1
@@ -17,6 +14,7 @@ PDF is the best format for storing and exchanging scanned documents.  Unfortunat
    introduction
    release_notes
    installation
+   optimizer
    languages
    jbig2
 
@@ -28,9 +26,18 @@ PDF is the best format for storing and exchanging scanned documents.  Unfortunat
    docker
    advanced
    batch
-   security
+   performance
+   pdfsecurity
    errors
 
+.. toctree::
+   :caption: Developers
+   :maxdepth: 2
+
+   api
+   plugins
+   apiref
+   contributing
 
 Indices and tables
 ==================

docs/installation.rst

@@ -1,3 +1,4 @@
+===================
 Installing OCRmyPDF
 ===================
 
@@ -7,21 +8,36 @@ Installing OCRmyPDF
 |latest|
 
 The easiest way to install OCRmyPDF is to follow the steps for your operating
-system/platform, although sometimes this version may be out of date.
+system/platform. This version may be out of date, however.
 
-If you want to use the latest version of OCRmyPDF, your best bet is to install
-the most recent version your platform provides, and then upgrade that version by
-installing the Python binary wheels.
+These platforms have one-liner installs:
+
++-----------------------------+-------------------------------+
+| Debian, Ubuntu              | ``apt install ocrmypdf``      |
++-----------------------------+-------------------------------+
+| Windows Subsystem for Linux | ``apt install ocrmypdf``      |
++-----------------------------+-------------------------------+
+| Fedora                      | ``dnf install ocrmypdf``      |
++-----------------------------+-------------------------------+
+| macOS                       | ``brew install ocrmypdf``     |
++-----------------------------+-------------------------------+
+| LinuxBrew                   | ``brew install ocrmypdf``     |
++-----------------------------+-------------------------------+
+| FreeBSD                     | ``pkg install py37-ocrmypdf`` |
++-----------------------------+-------------------------------+
+
+More detailed procedures are outlined below. If you want to do a manual
+install, or install a more recent version than your platform provides, read on.
 
 .. contents:: Platform-specific steps
     :depth: 2
     :local:
 
 Installing on Linux
--------------------
+===================
 
-Debian and Ubuntu 16.10 or newer
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Debian and Ubuntu 18.04 or newer
+--------------------------------
 
 .. |deb-stable| image:: https://repology.org/badge/version-for-repo/debian_stable/ocrmypdf.svg
     :alt: Debian 9 stable ("stretch")
@@ -32,118 +48,174 @@ Debian and Ubuntu 16.10 or newer
 .. |deb-unstable| image:: https://repology.org/badge/version-for-repo/debian_unstable/ocrmypdf.svg
     :alt: Debian unstable
 
-.. |ubu-1710| image:: https://repology.org/badge/version-for-repo/ubuntu_17_10/ocrmypdf.svg
-    :alt: Ubuntu 17.10
-
 .. |ubu-1804| image:: https://repology.org/badge/version-for-repo/ubuntu_18_04/ocrmypdf.svg
     :alt: Ubuntu 18.04 LTS
 
-.. |ubu-1810| image:: https://repology.org/badge/version-for-repo/ubuntu_18_10/ocrmypdf.svg
-    :alt: Ubuntu 18.10
+.. |ubu-2004| image:: https://repology.org/badge/version-for-repo/ubuntu_20_04/ocrmypdf.svg
+    :alt: Ubuntu 20.04 LTS
 
++-----------------------------------------------+
+| **OCRmyPDF versions in Debian & Ubuntu**      |
++-----------------------------------------------+
+| |latest|                                      |
++-----------------------------------------------+
+| |deb-stable| |deb-testing| |deb-unstable|     |
++-----------------------------------------------+
+| |ubu-1804| |ubu-2004|                         |
++-----------------------------------------------+
 
-+-------------------------------------------+
-| **OCRmyPDF versions in Debian & Ubuntu**  |
-+-------------------------------------------+
-| |latest|                                  |
-+-------------------------------------------+
-| |deb-stable| |deb-testing| |deb-unstable| |
-+-------------------------------------------+
-| |ubu-1710| |ubu-1804| |ubu-1810|          |
-+-------------------------------------------+
-
-Users of Debian 9 ("stretch") or later or Ubuntu 16.10 or later may simply
+Users of Debian 9 ("stretch") or later, or Ubuntu 18.04 or later, including users
+of Windows Subsystem for Linux, may simply
 
 .. code-block:: bash
 
     apt-get install ocrmypdf
 
-As indicated in the table above, Debian and Ubuntu releases may lag behind the latest version. If the version available for your platform is out of date, you could opt to install the latest version from source. See `Installing HEAD revision from sources`_.
+As indicated in the table above, Debian and Ubuntu releases may lag
+behind the latest version. If the version available for your platform is
+out of date, you could opt to install the latest version from source.
+See `Installing HEAD revision from
+sources <#installing-head-revision-from-sources>`__. Ubuntu 16.10 to 17.10
+inclusive also had ocrmypdf, but these versions are end of life.
 
-For full details on version availability for your platform, check the `Debian Package Tracker <https://tracker.debian.org/pkg/ocrmypdf>`_ or `Ubuntu launchpad.net <https://launchpad.net/ocrmypdf>`_.
+For full details on version availability for your platform, check the
+`Debian Package Tracker <https://tracker.debian.org/pkg/ocrmypdf>`__ or
+`Ubuntu launchpad.net <https://launchpad.net/ocrmypdf>`__.
 
 .. note::
 
-    OCRmyPDF for Debian and Ubuntu currently omit the JBIG2 encoder. OCRmyPDF works fine without it but will produce larger output files. If you build jbig2enc from source, ocrmypdf 7.0.0 and later will automatically detect it (specifically the ``jbig2`` binary) on the ``PATH``. To add JBIG2 encoding, see :ref:`jbig2`.
+   OCRmyPDF for Debian and Ubuntu currently omit the JBIG2 encoder.
+   OCRmyPDF works fine without it but will produce larger output files.
+   If you build jbig2enc from source, ocrmypdf 7.0.0 and later will
+   automatically detect it (specifically the ``jbig2`` binary) on the
+   ``PATH``. To add JBIG2 encoding, see :ref:`jbig2`.
 
 Fedora 29 or newer
-^^^^^^^^^^^^^^^^^^
+------------------
 
-.. |fedora-29| image:: https://repology.org/badge/version-for-repo/fedora29/ocrmypdf.svg
-    :alt: Fedora 29
+.. |fedora-31| image:: https://repology.org/badge/version-for-repo/fedora_31/ocrmypdf.svg
+    :alt: Fedora 31
+
+.. |fedora-32| image:: https://repology.org/badge/version-for-repo/fedora_32/ocrmypdf.svg
+    :alt: Fedora 32
 
 .. |fedora-rawhide| image:: https://repology.org/badge/version-for-repo/fedora_rawhide/ocrmypdf.svg
     :alt: Fedore Rawhide
 
++-----------------------------------------------+
+| **OCRmyPDF version**                          |
++-----------------------------------------------+
+| |latest|                                      |
++-----------------------------------------------+
+| |fedora-31| |fedora-32| |fedora-rawhide|      |
++-----------------------------------------------+
 
-+------------------------------+
-| **OCRmyPDF version**         |
-+------------------------------+
-| |latest|                     |
-+------------------------------+
-| |fedora-29| |fedora-rawhide| |
-+------------------------------+
-
-Users of Fedora 29 later may simply
+Users of Fedora 29 or later may simply
 
 .. code-block:: bash
 
     dnf install ocrmypdf
 
-For full details on version availability, check the `Fedora Package Tracker
-<https://apps.fedoraproject.org/packages/ocrmypdf>`_.
+For full details on version availability, check the `Fedora Package
+Tracker <https://apps.fedoraproject.org/packages/ocrmypdf>`__.
 
-If the version available for your platform is out of date, you could opt to
-install the latest version from source. See `Installing HEAD revision from
-sources`_.
+If the version available for your platform is out of date, you could opt
+to install the latest version from source. See `Installing HEAD revision
+from sources <#installing-head-revision-from-sources>`__.
 
 .. note::
 
-    OCRmyPDF for Fedora currently omits the JBIG2 encoder due to patent issues.
-    OCRmyPDF works fine without it but will produce larger output files. If you
-    build jbig2enc from source, ocrmypdf 7.0.0 and later will automatically
-    detect it on the ``PATH``. To add JBIG2 encoding, see `Installing the JBIG2
-    encoder <jbig2>`_.
+   OCRmyPDF for Fedora currently omits the JBIG2 encoder due to patent
+   issues. OCRmyPDF works fine without it but will produce larger output
+   files. If you build jbig2enc from source, ocrmypdf 7.0.0 and later
+   will automatically detect it on the ``PATH``. To add JBIG2 encoding,
+   see `Installing the JBIG2 encoder <jbig2>`__.
 
-Installing the latest version on Ubuntu 18.04 LTS
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+.. _ubuntu-lts-latest:
 
-Ubuntu 18.04 includes ocrmypdf 6.1.2. To install a more recent version, first
-install the system version to get most of the dependencies:
+Installing the latest version on Ubuntu 20.04 LTS
+-------------------------------------------------
+
+Ubuntu 20.04 includes ocrmypdf 9.6.0 - you can install that with ``apt``. To
+install a more recent version, uninstall the system-provided version of
+ocrmypdf, and install the following dependencies:
 
 .. code-block:: bash
 
-    sudo apt-get update
-    sudo apt-get install \
-        ocrmypdf \
-        python3-pip
+    sudo apt-get -y remove ocrmypdf  # remove system ocrmypdf, if installed
+    sudo apt-get -y update
+    sudo apt-get -y install \
+        ghostscript \
+        icc-profiles-free \
+        liblept5 \
+        libxml2 \
+        pngquant \
+        python3-pip \
+        tesseract-ocr \
+        zlib1g
 
-There are a few dependency changes between ocrmypdf 6.1.2 and 7.x. Let's get
-these, too.
+To install ocrmypdf for the system:
 
 .. code-block:: bash
 
-    sudo apt-get install \
-        libexempi3 \
-        pngquant
+    sudo pip3 install ocrmypdf
 
-Then install the most recent ocrmypdf for the local user and set the user's ``PATH`` to check for the user's Python packages.
+To install for the current user only:
 
 .. code-block:: bash
 
     export PATH=$HOME/.local/bin:$PATH
     pip3 install --user ocrmypdf
 
+Ubuntu 18.04 LTS
+----------------
+
+Ubuntu 18.04 includes ocrmypdf 6.1.2 - you can install that with ``apt``, but
+it is quite old now. To install a more recent version, uninstall the old version
+of ocrmypdf, and install the following dependencies:
+
+.. code-block:: bash
+
+    sudo apt-get -y remove ocrmypdf
+    sudo apt-get -y update
+    sudo apt-get -y install \
+        ghostscript \
+        icc-profiles-free \
+        liblept5 \
+        libxml2 \
+        pngquant \
+        python3-cffi \
+        python3-distutils \
+        python3-pkg-resources \
+        python3-reportlab \
+        qpdf \
+        tesseract-ocr \
+        zlib1g
+
+We will need a newer version of ``pip`` then was available for Ubuntu 18.04:
+
+.. code-block:: bash
+
+    wget https://bootstrap.pypa.io/get-pip.py && python3 get-pip.py
+
+Then install the most recent ocrmypdf for the local user and set the
+user's ``PATH`` to check for the user's Python packages.
+
+.. code-block:: bash
+
+    export PATH=$HOME/.local/bin:$PATH
+    python3 -m pip install --user ocrmypdf
+
 To add JBIG2 encoding, see :ref:`jbig2`.
 
 Ubuntu 16.04 LTS
-^^^^^^^^^^^^^^^^
+----------------
 
-No package is available for Ubuntu 16.04. OCRmyPDF 8.0 and newer require Python
-3.6. Ubuntu 16.04 ships Python 3.5, but you can install Python 3.6 on it. Or,
-you can skip Python 3.6 and install OCRmyPDF 7.x or older - for that procedure,
-please see the installation documentation for the version of OCRmyPDF you plan
-to use.
+No package is available for Ubuntu 16.04. OCRmyPDF 8.0 and newer require
+Python 3.6. Ubuntu 16.04 ships Python 3.5, but you can install Python
+3.6 on it. Or, you can skip Python 3.6 and install OCRmyPDF 7.x or older
+- for that procedure, please see the installation documentation for the
+version of OCRmyPDF you plan to use.
 
 **Install system packages for OCRmyPDF**
 
@@ -165,13 +237,13 @@ to use.
         tesseract-ocr \
         unpaper
 
-This will install a Python 3.6 binary at ``/usr/bin/python3.6`` alongside the
-system's Python 3.5. Do not remove the system Python. This will also install
-Tesseract 4.0 from a PPA, since the version available in Ubuntu 16.04 is too old
-for OCRmyPDF.
+This will install a Python 3.6 binary at ``/usr/bin/python3.6``
+alongside the system's Python 3.5. Do not remove the system Python. This
+will also install Tesseract 4.0 from a PPA, since the version available
+in Ubuntu 16.04 is too old for OCRmyPDF.
 
-Now install pip for Python 3.6. This will install the Python 3.6 version of
-``pip`` at ``/usr/local/bin/pip``.
+Now install pip for Python 3.6. This will install the Python 3.6 version
+of ``pip`` at ``/usr/local/bin/pip``.
 
 .. code-block:: bash
 
@@ -179,8 +251,9 @@ Now install pip for Python 3.6. This will install the Python 3.6 version of
 
 **Install OCRmyPDF**
 
-OCRmyPDF requires the locale to be set for UTF-8. **On some minimal Ubuntu
-installations systems**, it may be necessary to set the locale.
+OCRmyPDF requires the locale to be set for UTF-8. **On some minimal
+Ubuntu installations**, such as the Ubuntu 16.04 Docker images it may be
+necessary to set the locale.
 
 .. code-block:: bash
 
@@ -194,111 +267,156 @@ environment variable contains ``$HOME/.local/bin``.
 .. code-block:: bash
 
     export PATH=$HOME/.local/bin:$PATH
-    pip3 install --user ocrmypdf
+    pip3.6 install --user ocrmypdf
 
 To add JBIG2 encoding, see :ref:`jbig2`.
 
-Ubuntu 14.04 LTS
-^^^^^^^^^^^^^^^^
-
-Installing on Ubuntu 14.04 LTS (trusty) is more difficult than some other
-options, because of its age. Several backports are required. For explanations of
-some steps of this procedure, see the similar steps for Ubuntu 16.04.
-
-Install system dependencies:
-
-.. code-block:: bash
-
-    sudo apt-get update
-    sudo apt-get install \
-        software-properties-common python-software-properties \
-        zlib1g-dev \
-        libexempi3 \
-        libjpeg-dev \
-        libffi-dev \
-        pngquant \
-        qpdf
-
-We will need backports of Ghostscript 9.16, libav-11 (for unpaper 6.1),
-Tesseract 4.00 (alpha), and Python 3.6. This will replace Ghostscript and
-Tesseract 3.x on your system. Python 3.6 will be installed alongside the system
-Python 3.4.
-
-If you prefer to not modify your system in this matter, consider using a Docker
-container.
-
-.. code-block:: bash
-
-    sudo add-apt-repository ppa:vshn/ghostscript -y
-    sudo add-apt-repository ppa:heyarje/libav-11 -y
-    sudo add-apt-repository ppa:alex-p/tesseract-ocr -y
-    sudo add-apt-repository ppa:jonathonf/python-3.6 -y
-
-    sudo apt-get update
-
-    sudo apt-get install \
-        python3.6-dev \
-        ghostscript \
-        tesseract-ocr \
-        tesseract-ocr-eng \
-        libavformat56 libavcodec56 libavutil54 \
-        wget
-
-Now we need to install ``pip`` and let it install ocrmypdf:
-
-.. code-block:: bash
-
-    curl https://bootstrap.pypa.io/ez_setup.py -o - | python3.6 && python3.6 -m easy_install pip
-    pip3.6 install ocrmypdf
-
-These installation instructions omit the optional dependency ``unpaper``, which is only available at version 0.4.2 in Ubuntu 14.04. The author could not find a backport of ``unpaper``, and created a .deb package to do the job of installing unpaper 6.1 (for x86 64-bit only):
-
-.. code-block:: bash
-
-    wget -q 'https://www.dropbox.com/s/vaq0kbwi6e6au80/unpaper_6.1-1.deb?raw=1' -O unpaper_6.1-1.deb
-    sudo dpkg -i unpaper_6.1-1.deb
-
-To add JBIG2 encoding, see :ref:`jbig2`.
-
-ArchLinux (AUR)
-^^^^^^^^^^^^^^^
+Arch Linux (AUR)
+----------------
 
 .. image:: https://repology.org/badge/version-for-repo/aur/ocrmypdf.svg
     :alt: ArchLinux
     :target: https://repology.org/metapackage/ocrmypdf
 
-There is an `ArchLinux User Repository package for ocrmypdf <https://aur.archlinux.org/packages/ocrmypdf/>`_. You can use the following command.
+There is an `Arch User Repository (AUR) package for OCRmyPDF
+<https://aur.archlinux.org/packages/ocrmypdf/>`__.
+
+Installing AUR packages as root is not allowed, so you must first `setup a
+non-root user
+<https://wiki.archlinux.org/index.php/Users_and_groups#User_management>`__ and
+`configure sudo <https://wiki.archlinux.org/index.php/Sudo#Configuration>`__.
+The standard Docker image, ``archlinux/base:latest``, does **not** have a
+non-root user configured, so users of that image must follow these guides. If
+you are using a VM image, such as `the official Vagrant image
+<https://app.vagrantup.com/archlinux/boxes/archlinux>`__, this work may already
+be completed for you.
+
+Next you should install the `base-devel package group
+<https://www.archlinux.org/groups/x86_64/base-devel/>`__. This includes the
+standard tooling needed to build packages, such as a compiler and binary tools.
 
 .. code-block:: bash
 
-    yaourt -S ocrmypdf
+   sudo pacman -S base-devel
 
-If you have any difficulties with installation, check the repository package page.
+Now you are ready to install the OCRmyPDF package.
+
+.. code-block:: bash
+
+   curl -O https://aur.archlinux.org/cgit/aur.git/snapshot/ocrmypdf.tar.gz
+   tar xvzf ocrmypdf.tar.gz
+   cd ocrmypdf
+   makepkg -sri
+
+At this point you will have a working install of OCRmyPDF, but the Tesseract
+install won’t include any OCR language data. You can install `the
+tesseract-data package group
+<https://www.archlinux.org/groups/any/tesseract-data/>`__ to add all supported
+languages, or use that package listing to identify the appropriate package for
+your desired language.
+
+.. code-block:: bash
+
+   sudo pacman -S tesseract-data-eng
+
+As an alternative to this manual procedure, consider using an `AUR helper
+<https://wiki.archlinux.org/index.php/AUR_helpers>`__. Such a tool will
+automatically fetch, build and install the AUR package, resolve dependencies
+(including dependencies on AUR packages), and ease the upgrade procedure.
+
+If you have any difficulties with installation, check the repository package
+page.
+
+.. note::
+
+    The OCRmyPDF AUR package currently omits the JBIG2 encoder. OCRmyPDF works
+    fine without it but will produce larger output files. The encoder is
+    available from `the jbig2enc-git AUR package
+    <https://aur.archlinux.org/packages/jbig2enc-git/>`__ and may be installed
+    using the same series of steps as for the installation OCRmyPDF AUR
+    package. Alternatively, it may be built manually from source following the
+    instructions in `Installing the JBIG2 encoder <jbig2>`__.  If JBIG2 is
+    installed, OCRmyPDF 7.0.0 and later will automatically detect it.
+
+Alpine Linux
+------------
+
+.. image:: https://repology.org/badge/version-for-repo/alpine_edge/ocrmypdf.svg
+    :alt: Alpine Linux
+    :target: https://repology.org/metapackage/ocrmypdf
+
+To install OCRmyPDF for Alpine Linux:
+
+.. code-block:: bash
+
+    apk add ocrmypdf
+
+Mageia 7
+--------
+
+Install the following dependencies:
+
+.. code-block:: bash
+
+    # As root user
+    urpmi.update -a
+    urpmi \
+        ghostscript \
+        icc-profiles-openicc \
+        jbig2dec \
+        lib64leptonica5 \
+        pngquant \
+        python3-pip \
+        python3-cffi \
+        python3-distutils-extra \
+        python3-pkg-resources \
+        python3-reportlab \
+        qpdf \
+        tesseract \
+        tesseract-osd \
+        tesseract-eng \
+        tesseract-fra
+
+To install ocrmypdf for the system:
+
+    # As root user
+    pip3 install ocrmypdf
+    ldconfig
+
+Or, to install for the current user only:
+
+    export PATH=$HOME/.local/bin:$PATH
+    pip3 install --user ocrmypdf
 
 Other Linux packages
-^^^^^^^^^^^^^^^^^^^^
+--------------------
 
-See the `Repology <https://repology.org/metapackage/ocrmypdf/versions>`_ page.
+See the
+`Repology <https://repology.org/metapackage/ocrmypdf/versions>`__ page.
 
-In general, first install the OCRmyPDF package for your system, then optionally use the procedure `Installing with Python pip`_ to install a more recent version.
+In general, first install the OCRmyPDF package for your system, then
+optionally use the procedure `Installing with Python
+pip <#installing-with-python-pip>`__ to install a more recent version.
 
 Installing on macOS
--------------------
+===================
 
 Homebrew
-^^^^^^^^
+--------
 
 .. image:: https://img.shields.io/homebrew/v/ocrmypdf.svg
     :alt: homebrew
     :target: http://brewformulas.org/Ocrmypdf
 
-OCRmyPDF is now a standard `Homebrew <https://brew.sh>`_ formula. To install on macOS:
+OCRmyPDF is now a standard `Homebrew <https://brew.sh>`__ formula. To
+install on macOS:
 
 .. code-block:: bash
 
     brew install ocrmypdf
 
-This will include only the English language pack. If you need other languages you can optionally install them all:
+This will include only the English language pack. If you need other
+languages you can optionally install them all:
 
 .. code-block:: bash
 
@@ -306,18 +424,26 @@ This will include only the English language pack. If you need other languages yo
 
 .. note::
 
-    Users who previously installed OCRmyPDF on macOS using ``pip install ocrmypdf`` should remove the pip version (``pip3 uninstall ocrmypdf``) before switching to the Homebrew version.
+   Users who previously installed OCRmyPDF on macOS using
+   ``pip install ocrmypdf`` should remove the pip version
+   (``pip3 uninstall ocrmypdf``) before switching to the Homebrew
+   version.
 
 .. note::
 
-    Users who previously installed OCRmyPDF from the private tap should switch to the mainline version (``brew untap jbarlow83/ocrmypdf``) and install from there.
+   Users who previously installed OCRmyPDF from the private tap should
+   switch to the mainline version (``brew untap jbarlow83/ocrmypdf``)
+   and install from there.
 
 Manual installation on macOS
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+----------------------------
 
-These instructions probably work on all macOS supported by Homebrew.
+These instructions probably work on all macOS supported by Homebrew, and are
+for installing a more current version of OCRmyPDF than is available from
+Homebrew. Note that the Homebrew versions usually track the release versions
+fairly closely.
 
-If it's not already present, `install Homebrew <http://brew.sh/>`_.
+If it's not already present, `install Homebrew <http://brew.sh/>`__.
 
 Update Homebrew:
 
@@ -325,20 +451,18 @@ Update Homebrew:
 
     brew update
 
-Install or upgrade the required Homebrew packages, if any are missing. To do this, download the ``Brewfile`` that lists all of the dependencies to the current directory, and run ``brew bundle`` to process them (installing or upgrading as needed). ``Brewfile`` is a plain text file.
+Install or upgrade the required Homebrew packages, if any are missing.
+To do this, use ``brew edit ocrmypdf`` to obtain a recent list of Homebrew
+dependencies. You could also check the ``azure-pipelines.yml``.
 
-.. code-block:: bash
-
-    wget https://github.com/jbarlow83/OCRmyPDF/raw/master/.travis/Brewfile
-    brew bundle
-
-This will include the English, French, German and Spanish language packs. If you need other languages you can optionally install them all:
+This will include the English, French, German and Spanish language
+packs. If you need other languages you can optionally install them all:
 
 .. _macos-all-languages:
 
-.. code-block:: bash
+   .. code-block:: bash
 
-    brew install tesseract --with-all-languages  # Option 2: for all language packs
+    brew install tesseract-lang  # Option 2: for all language packs
 
 Update the homebrew pip:
 
@@ -364,94 +488,264 @@ The command line program should now be available:
 
     ocrmypdf --help
 
-Installing the Docker image
+Installing on Windows
+=====================
+
+Native Windows
+--------------
+
+.. note::
+
+    It is easier to install OCRmyPDF on Windows Subsystem for Linux.
+
+.. note::
+
+    Administrator privileges will be required for some of these steps.
+
+You must install the following for Windows:
+
+* Python 3.7 (64-bit) or later
+* Tesseract 4.0 or later
+* Ghostscript 9.50 or later
+
+You can install these with the Chocolatey package manager:
+
+* ``choco install python3``
+* ``choco install --pre tesseract``
+* ``choco install ghostscript``
+
+Also consider adding:
+
+* ``choco install pngquant``
+
+Windows 10 64-bit and 64-bit versions of applications are recommended. Earlier
+versions of Windows and 32-bit versions of these programs are not tested, and not
+supported at this time.
+
+OCRmyPDF will check for Tesseract-OCR and Ghostscript in your Program Files folder.
+If they are in some other location, you may need to modify the ``PATH``
+environment variable so Tesseract, Ghostscript, and other any optional executables can
+be found. You can enter it in the command line or
+`follow these directions <https://www.computerhope.com/issues/ch000549.htm#dospath>`_
+to make the change persistent and system-wide.
+
+You may then use pip to install ocrmypdf:
+
+* ``pip install ocrmypdf``
+
+Windows Subsystem for Linux
 ---------------------------
 
-For some users, installing the Docker image will be easier than installing all of OCRmyPDF's dependencies. For Windows, it is the only option.
+#. Install Ubuntu 18.04 for Windows Subsystem for Linux, if not already installed.
+#. Follow the procedure to install :ref:`OCRmyPDF on Ubuntu 18.04 <ubuntu-lts-latest>`.
+#. Open the Windows command prompt and create a symlink:
 
-See `OCRmyPDF Docker Image <docker>`_ for more information.
+.. code-block:: powershell
 
-Installing on Windows
----------------------
+    wsl sudo ln -s  /home/$USER/.local/bin/ocrmypdf /usr/local/bin/ocrmypdf
 
-Direct installation on Windows is not possible.  `Install the Docker <docker-install>`_ container as described above.  Ensure that your command prompt can run the docker "hello world" container.
+Then confirm that the expected version from PyPI (|latest|) is installed:
 
-It would probably not be too difficult to port on Windows.  The main reason this has been avoided is the difficulty of packaging and installing the various non-Python dependencies: Tesseract, QPDF, Ghostscript, Leptonica.  Pull requests to add or improve Windows support would be quite welcome.
+.. code-block:: powershell
+
+    wsl ocrmypdf --version
+
+You can then run OCRmyPDF in the Windows command prompt or Powershell, prefixing
+``wsl``, and call it from Windows programs or batch files.
+
+Cygwin64
+--------
+
+First install the the following prerequisite Cygwin packages using ``setup-x86_64.exe``::
+
+    python36 (or later)
+    python3?-devel
+    python3?-pip
+    python3?-lxml
+    python3?-imaging
+
+       (where 3? means match the version of python3 you installed)
+
+    gcc-g++
+    ghostscript (<=9.50 or >=9.52-2 see note below)
+    libexempi3
+    libexempi-devel
+    libffi6
+    libffi-devel
+    pngquant
+    qpdf
+    libqpdf-devel
+    tesseract-ocr
+    tesseract-ocr-devel
+
+.. note::
+
+    The Cygwin package for Ghostscript in versions 9.52 and
+    9.52-1 contained a bug that caused an exception to occur when
+    ocrmypdf invoked gs.  Make sure you have either 9.50 (or earlier)
+    or 9.52-2 (or later).
+
+Then open a Cygwin terminal (i.e. ``mintty``), run the following commands. Note
+that if you are using the version of ``pip`` that was installed with the Cygwin
+Python package, the command name will be ``pip3``.  If you have since updated
+``pip`` (with, for instance ``pip3 install --upgrade pip``) the the command is
+likely just ``pip`` instead of ``pip3``:
+
+.. code-block:: bash
+
+    pip3 install wheel
+    pip3 install ocrmypdf
+
+The optional dependency "unpaper" that is currently not available under Cygwin.
+Without it, certain options such as ``--clean`` will produce an error message.
+However, the OCR-to-text-layer functionality is available.
+
+Docker
+------
+
+You can also :ref:`Install the Docker <docker-install>` container on Windows. Ensure that
+your command prompt can run the docker "hello world" container.
+
+Installing on FreeBSD
+=====================
+
+.. image:: https://repology.org/badge/version-for-repo/freebsd/python:ocrmypdf.svg
+    :alt: FreeBSD
+    :target: https://repology.org/project/python:ocrmypdf/versions
+
+FreeBSD 11.3, 12.0, 12.1-RELEASE and 13.0-CURRENT are supported. Other
+versions likely work but have not been tested.
+
+.. code-block:: bash
+
+    pkg install py37-ocrmypdf
+
+To install a more recent version, you could attempt to first install the system
+version with ``pkg``, then use ``pip install --user ocrmypdf``.
+
+Installing the Docker image
+===========================
+
+For some users, installing the Docker image will be easier than
+installing all of OCRmyPDF's dependencies.
+
+See `OCRmyPDF Docker Image <docker>`__ for more information.
 
 Installing with Python pip
---------------------------
+==========================
 
-OCRmyPDF is delivered by PyPI because it is a convenient way to install the latest version. However, PyPI and ``pip`` cannot address the fact that ``ocrmypdf`` depends on certain non-Python system libraries and programs being instsalled.
+OCRmyPDF is delivered by PyPI because it is a convenient way to install
+the latest version. However, PyPI and ``pip`` cannot address the fact
+that ``ocrmypdf`` depends on certain non-Python system libraries and
+programs being instsalled.
 
-For best results, first install `your platform's version <https://repology.org/metapackage/ocrmypdf/versions>`_ of ``ocrmypdf``, using the instructions elsewhere in this document. Then you can use ``pip`` to get the latest version if your platform version is out of date. Chances are that this will satisfy most dependencies.
+For best results, first install `your platform's
+version <https://repology.org/metapackage/ocrmypdf/versions>`__ of
+``ocrmypdf``, using the instructions elsewhere in this document. Then
+you can use ``pip`` to get the latest version if your platform version
+is out of date. Chances are that this will satisfy most dependencies.
 
 Use ``ocrmypdf --version`` to confirm what version was installed.
 
-Then you can install the latest OCRmyPDF from the Python wheels. First try:
+Then you can install the latest OCRmyPDF from the Python wheels. First
+try:
 
 .. code-block:: bash
 
     pip3 install --user ocrmypdf
 
-You should then be able to run ``ocrmypdf --version`` and see that the latest version was located.
+You should then be able to run ``ocrmypdf --version`` and see that the
+latest version was located.
 
-Since ``pip3 install --user`` does not work correctly on some platforms, notably Ubuntu 16.04 and older, and the Homebrew version of Python, instead use this for a system wide installation:
+Since ``pip3 install --user`` does not work correctly on some platforms,
+notably Ubuntu 16.04 and older, and the Homebrew version of Python,
+instead use this for a system wide installation:
 
 .. code-block:: bash
 
     pip3 install ocrmypdf
 
+.. note::
+
+    AArch64 (ARM64) users: this process will be difficult because most
+    Python packages are not available as binary wheels for your platform.
+    You're probably better off using a platform install on Debian, Ubuntu,
+    or Fedora.
+
 Requirements for pip and HEAD install
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+-------------------------------------
 
-OCRmyPDF currently requires these external programs and libraries to be installed, and must be satisfied using the operating system package manager. ``pip`` cannot provide them.
+OCRmyPDF currently requires these external programs and libraries to be
+installed, and must be satisfied using the operating system package
+manager. ``pip`` cannot provide them.
 
-- Python 3.6 or newer
-- Ghostscript 9.15 or newer
-- qpdf 8.1.0 or newer
-- Tesseract 4.0.0-alpha or newer
+-  Python 3.6 or newer
+-  Ghostscript 9.15 or newer
+-  qpdf 8.1.0 or newer
+-  Tesseract 4.0.0-beta or newer
 
 As of ocrmypdf 7.2.1, the following versions are recommended:
 
-- Python 3.7
-- Ghostscript 9.23 or newer
-- qpdf 8.2.1
-- Tesseract 4.0.0 or newer
-- jbig2enc 0.29 or newer
-- pngquant 2.5 or newer
-- unpaper 6.1
+-  Python 3.7 or 3.8
+-  Ghostscript 9.23 or newer
+-  qpdf 8.2.1
+-  Tesseract 4.0.0 or newer
+-  jbig2enc 0.29 or newer
+-  pngquant 2.5 or newer
+-  unpaper 6.1
 
-jbig2enc, pngquant, and unpaper are optional. If missing certain features are disabled. OCRmyPDF will discover them as soon as they are available.
+jbig2enc, pngquant, and unpaper are optional. If missing certain
+features are disabled. OCRmyPDF will discover them as soon as they are
+available.
 
-**jbig2enc**, if present, will be used to optimize the encoding of monochrome images.  This can significantly reduce the file size of the output file.  It is not required.  `jbig2enc <https://github.com/agl/jbig2enc>`_ is not generally available for Ubuntu or Debian due to lingering concerns about patent issues, but can easily be built from source. To add JBIG2 encoding, see :ref:`jbig2`.
+**jbig2enc**, if present, will be used to optimize the encoding of
+monochrome images. This can significantly reduce the file size of the
+output file. It is not required.
+`jbig2enc <https://github.com/agl/jbig2enc>`__ is not generally
+available for Ubuntu or Debian due to lingering concerns about patent
+issues, but can easily be built from source. To add JBIG2 encoding, see
+:ref:`jbig2`.
 
-**pngquant**, if present, is optionally used to optimize the encoding of PNG-style images in PDFs (actually, any that are that losslessly encoded) by lossily quantizing to a smaller color palette. It is only activated then the ``--optimize`` argument is ``2`` or ``3``.
+**pngquant**, if present, is optionally used to optimize the encoding of
+PNG-style images in PDFs (actually, any that are that losslessly
+encoded) by lossily quantizing to a smaller color palette. It is only
+activated then the ``--optimize`` argument is ``2`` or ``3``.
 
-**unpaper**, if present, enables the ``--clean`` and ``--clean-final`` command line options.
-
-These are in addition to the Python packaging dependencies, meaning that unfortunately, the ``pip install`` command cannot satisfy all of them.
+**unpaper**, if present, enables the ``--clean`` and ``--clean-final``
+command line options.
 
+These are in addition to the Python packaging dependencies, meaning that
+unfortunately, the ``pip install`` command cannot satisfy all of them.
 
 Installing HEAD revision from sources
--------------------------------------
+=====================================
 
-If you have ``git`` and Python 3.6 or newer installed, you can install from source. When the ``pip`` installer runs, it will alert you if dependencies are missing.
+If you have ``git`` and Python 3.6 or newer installed, you can install
+from source. When the ``pip`` installer runs, it will alert you if
+dependencies are missing.
 
-If you prefer to build every from source, you will need to `build pikepdf from source <https://pikepdf.readthedocs.io/en/latest/installation.html#building-from-source>`_. First ensure you can build and install pikepdf.
+If you prefer to build every from source, you will need to `build
+pikepdf from
+source <https://pikepdf.readthedocs.io/en/latest/installation.html#building-from-source>`__.
+First ensure you can build and install pikepdf.
 
-To install the HEAD revision from sources in the current Python 3 environment:
+To install the HEAD revision from sources in the current Python 3
+environment:
 
 .. code-block:: bash
 
     pip3 install git+https://github.com/jbarlow83/OCRmyPDF.git
 
-Or, to install in `development mode <https://pythonhosted.org/setuptools/setuptools.html#development-mode>`_,  allowing customization of OCRmyPDF, use the ``-e`` flag:
+Or, to install in `development
+mode <https://pythonhosted.org/setuptools/setuptools.html#development-mode>`__,
+allowing customization of OCRmyPDF, use the ``-e`` flag:
 
 .. code-block:: bash
 
     pip3 install -e git+https://github.com/jbarlow83/OCRmyPDF.git
 
-You may find it easiest to install in a virtual environment, rather than system-wide:
+You may find it easiest to install in a virtual environment, rather than
+system-wide:
 
 .. code-block:: bash
 
@@ -461,8 +755,8 @@ You may find it easiest to install in a virtual environment, rather than system-
     cd OCRmyPDF
     pip3 install .
 
-However, ``ocrmypdf`` will only be accessible on the system PATH
-when you activate the virtual environment.
+However, ``ocrmypdf`` will only be accessible on the system PATH when
+you activate the virtual environment.
 
 To run the program:
 
@@ -476,7 +770,7 @@ dependencies. Older version than the ones mentioned in the release notes
 are likely not to be compatible to OCRmyPDF.
 
 For development
-^^^^^^^^^^^^^^^
+---------------
 
 To install all of the development and test requirements:
 
@@ -490,3 +784,19 @@ To install all of the development and test requirements:
     pip install -r requirements/dev.txt -r requirements/test.txt
 
 To add JBIG2 encoding, see :ref:`jbig2`.
+
+Shell completions
+=================
+
+Completions for ``bash`` and ``fish`` are available in the project's
+``misc/completion`` folder. The ``bash`` completions are likely ``zsh``
+compatible but this has not been confirmed. Package maintainers, please
+install these at the appropriate locations for your system.
+
+To manually install the ``bash`` completion, copy
+``misc/completion/ocrmypdf.bash`` to ``/etc/bash_completion.d/ocrmypdf``
+(rename the file).
+
+To manually install the ``fish`` completion, copy
+``misc/completion/ocrmypdf.fish`` to
+``~/.config/fish/completions/ocrmypdf.fish``.

docs/introduction.rst

@@ -1,119 +1,228 @@
+============
 Introduction
 ============
-OCRmyPDF is a Python 3 package that adds OCR layers to PDFs.
+
+OCRmyPDF is a Python 3 application and library that adds OCR layers to PDFs.
 
 About OCR
----------
+=========
 
-`Optical character recognition <https://en.wikipedia.org/wiki/Optical_character_recognition>`_ is technology that converts images of typed or handwritten text, such as in a scanned document, to computer text that can be searched and copied.
+`Optical character
+recognition <https://en.wikipedia.org/wiki/Optical_character_recognition>`__
+is technology that converts images of typed or handwritten text, such as
+in a scanned document, to computer text that can be selected, searched and copied.
 
-OCRmyPDF uses `Tesseract <https://github.com/tesseract-ocr/tesseract>`_, the best available open source OCR engine, to perform OCR.
+OCRmyPDF uses
+`Tesseract <https://github.com/tesseract-ocr/tesseract>`__, the best
+available open source OCR engine, to perform OCR.
 
 .. _raster-vector:
 
 About PDFs
-----------
+==========
 
-PDFs are page description files that attempts to preserve a layout exactly. They  contain `vector graphics <http://vector-conversions.com/vectorizing/raster_vs_vector.html>`_ that can contain raster objects such as scanned images. Because PDFs can contain multiple pages (unlike many image formats) and can contain fonts and text, it is a good formats for exchanging scanned documents.
+PDFs are page description files that attempts to preserve a layout
+exactly. They contain `vector
+graphics <http://vector-conversions.com/vectorizing/raster_vs_vector.html>`__
+that can contain raster objects such as scanned images. Because PDFs can
+contain multiple pages (unlike many image formats) and can contain fonts
+and text, it is a good formats for exchanging scanned documents.
 
-.. image:: bitmap_vs_svg.svg
+|image|
 
-A PDF page might contain multiple images, even if it only appears to have one image.  Some scanners or scanning software will segment pages into monochromatic text and color regions for example, to improve the compression ratio and appearance of the page.
-
-Rasterizing a PDF is the process of generating an image suitable for display or analyzing with an OCR engine.  OCR engines like Tesseract work with images, not vector objects.
+A PDF page might contain multiple images, even if it only appears to
+have one image. Some scanners or scanning software will segment pages
+into monochromatic text and color regions for example, to improve the
+compression ratio and appearance of the page.
 
+Rasterizing a PDF is the process of generating an image suitable for
+display or analyzing with an OCR engine. OCR engines like Tesseract work
+with images, not vector objects.
 
 About PDF/A
------------
+===========
 
-`PDF/A <https://en.wikipedia.org/wiki/PDF/A>`_ is an ISO-standardized subset of the full PDF specification that is designed for archiving (the 'A' stands for Archive).  PDF/A differs from PDF primarily by omitting features that would make it difficult to read the file in the future, such as embedded Javascript, video, audio and references to external fonts.  All fonts and resources needed to interpret the PDF must be contained within it. Because PDF/A disables Javascript and other types of embedded content, it is probably more secure.
+`PDF/A <https://en.wikipedia.org/wiki/PDF/A>`__ is an ISO-standardized
+subset of the full PDF specification that is designed for archiving (the
+'A' stands for Archive). PDF/A differs from PDF primarily by omitting
+features that would make it difficult to read the file in the future,
+such as embedded Javascript, video, audio and references to external
+fonts. All fonts and resources needed to interpret the PDF must be
+contained within it. Because PDF/A disables Javascript and other types
+of embedded content, it is probably more secure.
 
 There are various conformance levels and versions, such as "PDF/A-2b".
 
-Generally speaking, the best format for scanned documents is PDF/A. Some governments and jurisdictions, US Courts in particular, `mandate the use of PDF/A <https://pdfblog.com/2012/02/13/what-is-pdfa/>`_ for scanned documents.
+Generally speaking, the best format for scanned documents is PDF/A. Some
+governments and jurisdictions, US Courts in particular, `mandate the use
+of PDF/A <https://pdfblog.com/2012/02/13/what-is-pdfa/>`__ for scanned
+documents.
 
-Since most people who scan documents are interested in reading them indefinitely into the future, OCRmyPDF generates PDF/A-2b by default.
-
-PDF/A has a few drawbacks.  Some PDF viewers include an alert that the file is a PDF/A, which may confuse some users.  It also tends to produce larger files than PDF, because it embeds certain resources even if they are commonly available. PDF/A files can be digitally signed, but may not be encrypted, to ensure they can be read in the future.  Fortunately, converting from PDF/A to a regular PDF is trivial, and any PDF viewer can view PDF/A.
+Since most people who scan documents are interested in reading them
+indefinitely into the future, OCRmyPDF generates PDF/A-2b by default.
 
+PDF/A has a few drawbacks. Some PDF viewers include an alert that the
+file is a PDF/A, which may confuse some users. It also tends to produce
+larger files than PDF, because it embeds certain resources even if they
+are commonly available. PDF/A files can be digitally signed, but may not
+be encrypted, to ensure they can be read in the future. Fortunately,
+converting from PDF/A to a regular PDF is trivial, and any PDF viewer
+can view PDF/A.
 
 What OCRmyPDF does
-------------------
+==================
 
-OCRmyPDF analyzes each page of a PDF to determine the colorspace and resolution (DPI) needed to capture all of the information on that page without losing content.  It uses `Ghostscript <http://ghostscript.com/>`_ to rasterize the page, and then performs on OCR on the rasterized image to create an OCR "layer". The layer is then grafted back onto the original PDF.
+OCRmyPDF analyzes each page of a PDF to determine the colorspace and
+resolution (DPI) needed to capture all of the information on that page
+without losing content. It uses
+`Ghostscript <http://ghostscript.com/>`__ to rasterize the page, and
+then performs on OCR on the rasterized image to create an OCR "layer".
+The layer is then grafted back onto the original PDF.
 
-While one can use a program like Ghostscript or ImageMagick to get an image and put the image through Tesseract, that actually creates a new PDF and many details may be lost. OCRmyPDF can produce a minimally changed PDF as output.
+While one can use a program like Ghostscript or ImageMagick to get an
+image and put the image through Tesseract, that actually creates a new
+PDF and many details may be lost. OCRmyPDF can produce a minimally
+changed PDF as output.
 
-OCRmyPDF also some image processing options like deskew which improve the appearance of files and quality of OCR. When these are used, the OCR layer is grafted onto the processed image instead.
-
-By default, OCRmyPDF produces archival PDFs – PDF/A, which are a stricter subset of PDF features designed for long term archives. If regular PDFs are desired, this can be disabled with ``--output-type pdf``.
+OCRmyPDF also some image processing options like deskew which improve
+the appearance of files and quality of OCR. When these are used, the OCR
+layer is grafted onto the processed image instead.
 
+By default, OCRmyPDF produces archival PDFs – PDF/A, which are a
+stricter subset of PDF features designed for long term archives. If
+regular PDFs are desired, this can be disabled with
+``--output-type pdf``.
 
 Why you shouldn't do this manually
-----------------------------------
+==================================
 
-A PDF is similar to an HTML file, in that it contains document structure along with images.  Sometimes a PDF does nothing more than present a full page image, but often there is additional content that would be lost.
+A PDF is similar to an HTML file, in that it contains document structure
+along with images. Sometimes a PDF does nothing more than present a full
+page image, but often there is additional content that would be lost.
 
 A manual process could work like either of these:
 
-1. Rasterize each page as an image, OCR the images, and combine the output into a PDF. This preserves the layout of each page, but resamples all images (possibly losing quality, increasing file size, introducing compression artifacts, etc.).
+1. Rasterize each page as an image, OCR the images, and combine the
+   output into a PDF. This preserves the layout of each page, but
+   resamples all images (possibly losing quality, increasing file size,
+   introducing compression artifacts, etc.).
+2. Extract each image, OCR, and combine the output into a PDF. This
+   loses the context in which images are used in the PDF, meaning that
+   cropping, rotation and scaling of pages may be lost. Some scanned
+   PDFs use multiple images segmented into black and white, grayscale
+   and color regions, with stencil masks to prevent overlap, as this can
+   enhance the appearance of a file while reducing file size. Clearly,
+   reassembling these images will be easy. This also loses and text or
+   vector art on any pages in a PDF with both scanned and pure digital
+   content.
 
-2. Extract each image, OCR, and combine the output into a PDF. This loses the context in which images are used in the PDF, meaning that cropping, rotation and scaling of pages may be lost. Some scanned PDFs use multiple images segmented into black and white, grayscale and color regions, with stencil masks to prevent overlap, as this can enhance the appearance of a file while reducing file size. Clearly, reassembling these images will be easy. This also loses and text or vector art on any pages in a PDF with both scanned and pure digital content.
+In the case of a PDF that is nothing other than a container of images
+(no rotation, scaling, cropping, one image per page), the second
+approach can be lossless.
 
-In the case of a PDF that is nothing other than a container of images (no rotation, scaling, cropping, one image per page), the second approach can be lossless.
-
-OCRmyPDF uses several strategies depending on input options and the input PDF itself, but generally speaking it rasterizes a page for OCR and then grafts the OCR back onto the original. As such it can handle complex PDFs and still preserve their contents as much as possible.
-
-OCRmyPDF also supports a many, many edge cases that have cropped over several years of development. We support PDF features like images inside of Form XObjects, and pages with UserUnit scaling. We support rare image formats like non-monochrome 1-bit images. We warn about files you may not to OCR. Thanks to pikepdf and QPDF, we auto-repair PDFs that are damaged. (Not that you need to know what any of these are! You should be able to throw any PDF at it.)
+OCRmyPDF uses several strategies depending on input options and the
+input PDF itself, but generally speaking it rasterizes a page for OCR
+and then grafts the OCR back onto the original. As such it can handle
+complex PDFs and still preserve their contents as much as possible.
 
+OCRmyPDF also supports a many, many edge cases that have cropped over
+several years of development. We support PDF features like images inside
+of Form XObjects, and pages with UserUnit scaling. We support rare image
+formats like non-monochrome 1-bit images. We warn about files you may
+not to OCR. Thanks to pikepdf and QPDF, we auto-repair PDFs that are
+damaged. (Not that you need to know what any of these are! You should be
+able to throw any PDF at it.)
 
 Limitations
------------
+===========
 
-OCRmyPDF is limited by the Tesseract OCR engine.  As such it experiences these limitations, as do any other programs that rely on Tesseract:
+OCRmyPDF is limited by the Tesseract OCR engine. As such it experiences
+these limitations, as do any other programs that rely on Tesseract:
 
-* The OCR is not as accurate as commercial solutions such as Abbyy.
-* It is not capable of recognizing handwriting.
-* It may find gibberish and report this as OCR output.
-* If a document contains languages outside of those given in the ``-l LANG`` arguments, results may be poor.
-* It is not always good at analyzing the natural reading order of documents. For example, it may fail to recognize that a document contains two columns, and may try to join text across columns.
-* Poor quality scans may produce poor quality OCR. Garbage in, garbage out.
-* It does not expose information about what font family text belongs to.
+-  The OCR is not as accurate as commercial solutions such as Abbyy.
+-  It is not capable of recognizing handwriting.
+-  It may find gibberish and report this as OCR output.
+-  If a document contains languages outside of those given in the
+   ``-l LANG`` arguments, results may be poor.
+-  It is not always good at analyzing the natural reading order of
+   documents. For example, it may fail to recognize that a document
+   contains two columns, and may try to join text across columns.
+-  Poor quality scans may produce poor quality OCR. Garbage in, garbage
+   out.
+-  It does not expose information about what font family text belongs
+   to.
 
 OCRmyPDF is also limited by the PDF specification:
 
-* PDF encodes the position of text glyphs but does not encode document structure.  There is no markup that divides a document in sections, paragraphs, sentences, or even words (since blank spaces are not represented). As such all elements of document structure including the spaces between words must be derived heuristically.  Some PDF viewers do a better job of this than others.
-* Because some popular open source PDF viewers have a particularly hard time with spaces betweem words, OCRmyPDF appends a space to each text element as a workaround (when using ``--pdf-renderer hocr``). While this mixes document structure with graphical information that ideally should be left to the PDF viewer to interpret, it improves compatibility with some viewers and does not cause problems for better ones.
+-  PDF encodes the position of text glyphs but does not encode document
+   structure. There is no markup that divides a document in sections,
+   paragraphs, sentences, or even words (since blank spaces are not
+   represented). As such all elements of document structure including
+   the spaces between words must be derived heuristically. Some PDF
+   viewers do a better job of this than others.
+-  Because some popular open source PDF viewers have a particularly hard
+   time with spaces between words, OCRmyPDF appends a space to each text
+   element as a workaround (when using ``--pdf-renderer hocr``). While
+   this mixes document structure with graphical information that ideally
+   should be left to the PDF viewer to interpret, it improves
+   compatibility with some viewers and does not cause problems for
+   better ones.
 
 Ghostscript also imposes some limitations:
 
-* PDFs containing JBIG2-encoded content will be converted to CCITT Group4 encoding, which has lower compression ratios, if Ghostscript PDF/A is enabled.
-* PDFs containing JPEG 2000-encoded content will be converted to JPEG encoding, which may introduce compression artifacts, if Ghostscript PDF/A is enabled.
-* Ghostscript may transcode grayscale and color images, either lossy to lossless or lossless to lossy, based on an internal algorithm. This behavior can be suppressed by setting ``--pdfa-image-compression`` to ``jpeg`` or ``lossless`` to set all images to one type or the other. Ghostscript has no option to maintain the input image's format. (Ghostscript 9.25+ can copy JPEG images without transcoding them; earlier versions will transcode.)
-* Ghostscript's PDF/A conversion removes any XMP metadata that is not one of the standard XMP metadata namespaces for PDFs. In particular, PRISM Metdata is removed.
+-  PDFs containing JBIG2-encoded content will be converted to CCITT
+   Group4 encoding, which has lower compression ratios, if Ghostscript
+   PDF/A is enabled.
+-  PDFs containing JPEG 2000-encoded content will be converted to JPEG
+   encoding, which may introduce compression artifacts, if Ghostscript
+   PDF/A is enabled.
+-  Ghostscript may transcode grayscale and color images, either lossy to
+   lossless or lossless to lossy, based on an internal algorithm. This
+   behavior can be suppressed by setting ``--pdfa-image-compression`` to
+   ``jpeg`` or ``lossless`` to set all images to one type or the other.
+   Ghostscript has no option to maintain the input image's format.
+   (Ghostscript 9.25+ can copy JPEG images without transcoding them;
+   earlier versions will transcode.)
+-  Ghostscript's PDF/A conversion removes any XMP metadata that is not
+   one of the standard XMP metadata namespaces for PDFs. In particular,
+   PRISM Metdata is removed.
 
 Regarding OCRmyPDF itself:
 
-* PDFs that use transparency are not currently represented in the test suite
-* The Python API exported by ``import ocrmypdf`` is design to help scripts that use OCRmyPDF but is not currently capable of running OCRmyPDF jobs due to limitations in an underlying library.
+-  PDFs that use transparency are not currently represented in the test
+   suite
 
 Similar programs
-----------------
+================
 
-To the author's knowledge, OCRmyPDF is the most feature-rich and thoroughly tested command line OCR PDF conversion tool. If it does not meet your needs, contributions and suggestions are welcome. If not, consider one of these similar open source programs:
+To the author's knowledge, OCRmyPDF is the most feature-rich and
+thoroughly tested command line OCR PDF conversion tool. If it does not
+meet your needs, contributions and suggestions are welcome. If not,
+consider one of these similar open source programs:
 
-* pdf2pdfocr
-* pdfsandwich
-* pypdfocr
-* pdfbeads
+-  pdf2pdfocr
+-  pdfsandwich
+-  pypdfocr
+-  pdfbeads
 
 Web front-ends
---------------
+==============
 
-The Docker image ``ocrmypdf-alpine`` provides a web service front-end that allows files to submitted over HTTP and the results "downloaded". This is an HTTP server intended to simplify web services deployments; it is not intended to be deployed on the public internet and no real security measures to speak of.
+The Docker image ``ocrmypdf`` provides a web service front-end
+that allows files to submitted over HTTP and the results "downloaded".
+This is an HTTP server intended to simplify web services deployments; it
+is not intended to be deployed on the public internet and no real
+security measures to speak of.
 
 In addition, the following third-party integrations are available:
 
-* `Nextcloud OCR <https://github.com/janis91/ocr>`_ is a free software plugin for the Nextcloud private cloud software
+-  `Nextcloud OCR <https://github.com/janis91/ocr>`__ is a free software
+   plugin for the Nextcloud private cloud software
 
-OCRmyPDF is not designed to be secure against malware-bearing PDFs (see `Using OCRmyPDF online <ocr-service>`_). Users should ensure they comply with OCRmyPDF's licenses and the licenses of all dependencies. In particular, OCRmyPDF requires Ghostscript, which is licensed under AGPLv3.
+OCRmyPDF is not designed to be secure against malware-bearing PDFs (see
+`Using OCRmyPDF online <ocr-service>`__). Users should ensure they
+comply with OCRmyPDF's licenses and the licenses of all dependencies. In
+particular, OCRmyPDF requires Ghostscript, which is licensed under
+AGPLv3.
+
+.. |image| image:: images/bitmap_vs_svg.svg

docs/jbig2.rst

@@ -1,35 +1,55 @@
 .. _jbig2:
 
+============================
 Installing the JBIG2 encoder
 ============================
 
-Most Linux distributions do not include a JBIG2 encoder since JBIG2 encoding was patented for a long time. All known JBIG2 US patents have expired as of 2017, but it is possible that unknown patents exist.
+Most Linux distributions do not include a JBIG2 encoder since JBIG2
+encoding was patented for a long time. All known JBIG2 US patents have
+expired as of 2017, but it is possible that unknown patents exist.
 
-JBIG2 encoding is recommended for OCRmyPDF and is used to losslessly create smaller PDFs. If JBIG2 encoding not available, lower quality encodings will be used.
+JBIG2 encoding is recommended for OCRmyPDF and is used to losslessly
+create smaller PDFs. If JBIG2 encoding not available, lower quality
+encodings will be used.
 
-JBIG2 decoding is not patented and is performed automatically by most PDF viewers. It is widely supported has been part of the PDF specification since 2001.
+JBIG2 decoding is not patented and is performed automatically by most
+PDF viewers. It is widely supported has been part of the PDF
+specification since 2001.
 
-On macOS, Homebrew packages jbig2enc and OCRmyPDF includes it by default. The Docker image for OCRmyPDF also builds its own JBIG2 encoder from source.
+On macOS, Homebrew packages jbig2enc and OCRmyPDF includes it by
+default. The Docker image for OCRmyPDF also builds its own JBIG2 encoder
+from source.
 
 For all other Linux, you must build a JBIG2 encoder from source:
 
 .. code-block:: bash
 
-    git clone https://github.com/agl/jbig2enc
-    cd jbig2enc
-    ./autogen.sh
-    ./configure && make
-    [sudo] make install
+   git clone https://github.com/agl/jbig2enc
+   cd jbig2enc
+   ./autogen.sh
+   ./configure && make
+   [sudo] make install
 
 .. _jbig2-lossy:
 
 Lossy mode JBIG2
-----------------
+================
 
-OCRmyPDF provides lossy mode JBIG2 as an advanced feature. Users should `review the technical concerns with JBIG2 in lossy mode <https://abbyy.technology/en:kb:tip:jbig2_compression_and_ocr>`_ and decide if this feature is acceptable for their use case.
+OCRmyPDF provides lossy mode JBIG2 as an advanced feature. Users should
+`review the technical concerns with JBIG2 in lossy
+mode <https://abbyy.technology/en:kb:tip:jbig2_compression_and_ocr>`__
+and decide if this feature is acceptable for their use case.
 
-JBIG2 lossy mode does achieve higher compression ratios than any other monochrome (bitonal) compression technology; for large text documents the savings are considerable. JBIG2 lossless still gives great compression ratios and is a major improvement over the older CCITT G4 standard. As explained above, there is some risk of substitution errors.
+JBIG2 lossy mode does achieve higher compression ratios than any other
+monochrome (bitonal) compression technology; for large text documents
+the savings are considerable. JBIG2 lossless still gives great
+compression ratios and is a major improvement over the older CCITT G4
+standard. As explained above, there is some risk of substitution errors.
 
-To turn on JBIG2 lossy mode, add the argument ``--jbig2-lossy``. ``--optimize {1,2,3}`` are necessary for the argument to take effect also required. Also, a JBIG2 encoder must be installed as described in the previous section.
+To turn on JBIG2 lossy mode, add the argument ``--jbig2-lossy``.
+``--optimize {1,2,3}`` are necessary for the argument to take effect
+also required. Also, a JBIG2 encoder must be installed as described in
+the previous section.
 
-*Due to an oversight, ocrmypdf v7.0 and v7.1 used lossy mode by default.*
+*Due to an oversight, ocrmypdf v7.0 and v7.1 used lossy mode by
+default.*

docs/languages.rst

@@ -1,16 +1,29 @@
 .. _lang-packs:
 
+====================================
 Installing additional language packs
 ====================================
 
-OCRmyPDF uses Tesseract for OCR, and relies on its language packs for languages other than English.
+OCRmyPDF uses Tesseract for OCR, and relies on its language packs for all languages.
+On most platforms, English is installed with Tesseract by default, but not always.
 
-Tesseract supports `most languages <https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#languages>`_.
+Tesseract supports `most
+languages <https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#languages>`__.
+Languages are identified by standardized three-letter codes (called ISO 639-2 Alpha-3).
+Tesseract's documentation also lists the three-letter code for your language.
+Some are anglicized, e.g. Spanish is ``spa`` rather than ``esp``, while others
+are not, e.g. German is ``deu``.
 
-For Linux users, you can often find packages that provide language packs:
+After you have installed a language pack, you can use it ``ocrmypdf -l <language>``,
+for example ``ocrmypdf -l spa``. For multilingual documents, you can specify
+all languages to be expected, e.g. ``ocrmypdf -l eng+fra`` for English and French.
+English is assumed by default unless other language(s) are specified.
+
+For Linux users, you can often find packages that provide language
+packs:
 
 Debian and Ubuntu users
------------------------
+=======================
 
 .. code-block:: bash
 
@@ -20,11 +33,13 @@ Debian and Ubuntu users
    # Install Chinese Simplified language pack
    apt-get install tesseract-ocr-chi-sim
 
-You can then pass the ``-l LANG`` argument to OCRmyPDF to give a hint as to what languages it should search for. Multiple
-languages can be requested using either ``-l eng+fre`` (English and French) or ``-l eng -l fre``.
+You can then pass the ``-l LANG`` argument to OCRmyPDF to give a hint as
+to what languages it should search for. Multiple languages can be
+requested using either ``-l eng+fre`` (English and French) or
+``-l eng -l fre``.
 
 Fedora users
-------------
+============
 
 .. code-block:: bash
 
@@ -34,16 +49,25 @@ Fedora users
    # Install Chinese Simplified language pack
    dnf install tesseract-langpack-chi_sim
 
-You can then pass the ``-l LANG`` argument to OCRmyPDF to give a hint as to
-what languages it should search for. Multiple languages can be requested using
-either ``-l eng+fre`` (English and French) or ``-l eng -l fre``.
+You can then pass the ``-l LANG`` argument to OCRmyPDF to give a hint as
+to what languages it should search for. Multiple languages can be
+requested using either ``-l eng+fre`` (English and French) or
+``-l eng -l fre``.
 
 macOS users
------------
+===========
 
-You can install additional language packs by :ref:`installing Tesseract using Homebrew with all language packs <macos-all-languages>`.
+You can install additional language packs by
+:ref:`installing Tesseract using Homebrew with all language packs <macos-all-languages>`.
 
 Docker users
-------------
+============
 
-Users of the OCRmyPDF Docker image should install language packs into a derived Docker image as :ref:`described in that section <docker-lang-packs>`.
+Users of the OCRmyPDF Docker image should install language packs into a
+derived Docker image as
+:ref:`described in that section <docker-lang-packs>`.
+
+Windows users
+=============
+
+The Tesseract installer provided by Chocolatey already includes 100 languages.

docs/optimizer.rst

@@ -0,0 +1,75 @@
+================
+PDF optimization
+================
+
+OCRmyPDF includes an image-oriented PDF optimizer. By default, the optimizer
+runs with safe settings with the goal of improving compression at no loss of
+quality. At higher optimization levels, lossy optimizations may be applied and
+tuned. Optimization occurs after OCR, and only if OCR succeeded.  It does not
+perform other possible optimizations such as deduplicating resources,
+consolidating fonts, simplifying vector drawings, or anything of that nature.
+
+Optimization ranges from ``-O0`` through ``-O3``, where ``0`` disables
+optimization and ``3`` implements all options. ``1``, the default, performs only
+safe and lossless optimizations. (This is similar to GCC's optimization
+parameter.) The exact type of optimizations performed will vary over time.
+
+PDF optimization requires third-party, optional tools for certain optimizations.
+If these are not installed or cannot be found by OCRmyPDF, optimization will not
+be as good.
+
+Optimizations that always occurs
+================================
+
+OCRmyPDF will automatically replace obsolete or inferior compression schemes
+such as RLE or LZW with superior schemes such as Deflate and converting
+monochrome images to CCITT G4. Since this is harmless it always occurs and there
+is no way to disable it. Other non-image compressed objects are compressed as
+well.
+
+Fast web view
+=============
+
+OCRmyPDF automatically optimizes PDFs for "fast web view" in Adobe Acrobat's
+parlance, or equivalently, linearizes PDFs so that the resources they reference
+are presented in the order a viewer needs them for sequential display. This
+reduces the latency of viewing a PDF both online and from local storage. This
+actually slightly increases the file size.
+
+To disable this optimization and all others, use ``ocrmypdf --optimize 0 ...``
+or the shorthand ``-O0``.
+
+Lossless optimizations
+======================
+
+At optimization level ``-O1`` (the default), OCRmyPDF will also attempt lossless
+image optimization.
+
+If a JBIG2 encoder is available, then monochrome images will be converted to
+JBIG2, with the potential for huge savings on large black and white images,
+since JBIG2 is far more efficient than any other monochrome (bi-level)
+compression. (All known US patents related to JBIG2 have probably expired, but
+it remains the responsibility of the user to supply a JBIG2 encoder such as
+`jbig2enc <https://github.com/agl/jbig2enc>`__. OCRmyPDF does not implement
+JBIG2 encoding on its own.)
+
+OCRmyPDF currently does not attempt to recompress losslessly compressed objects
+more aggressively.
+
+Lossy optimizations
+===================
+
+At optimization level ``-O2`` and ``-O3``, OCRmyPDF will some attempt lossy
+image optimization.
+
+If ``pngquant`` is installed, OCRmyPDF will use it to perform quantize paletted
+images to reduce their size.
+
+The quality of JPEGs may be lowered, on the assumption that a lower quality
+image may be suitable for storage after OCR.
+
+It is not possible to optimize all image types. Uncommon image types may be
+skipped by the optimizer.
+
+OCRmyPDF provides :ref:`lossy mode JBIG2 <jbig2-lossy>` as an advanced feature
+that additional requires the argument ``--jbig2-lossy``.

docs/pdfsecurity.rst

@@ -0,0 +1,161 @@
+===================
+PDF security issues
+===================
+
+   OCRmyPDF should only be used on PDFs you trust. It is not designed to
+   protect you against malware.
+
+Recognizing that many users have an interest in handling PDFs and
+applying OCR to PDFs they did not generate themselves, this article
+discusses the security implications of PDFs and how users can protect
+themselves.
+
+The disclaimer applies: this software has no warranties of any kind.
+
+PDFs may contain malware
+========================
+
+PDF is a rich, complex file format. The official PDF 1.7 specification,
+ISO 32000:2008, is hundreds of pages long and references several annexes
+each of which are similar in length. PDFs can contain video, audio, XML,
+JavaScript and other programming, and forms. In some cases, they can
+open internet connections to pre-selected URLs. All of these possible
+attack vectors.
+
+In short, PDFs `may contain
+viruses <https://security.stackexchange.com/questions/64052/can-a-pdf-file-contain-a-virus>`__.
+
+This
+`article <https://theinvisiblethings.blogspot.ca/2013/02/converting-untrusted-pdfs-into-trusted.html>`__
+describes a high-paranoia method which allows potentially hostile PDFs
+to be viewed and rasterized safely in a disposable virtual machine. A
+trusted PDF created in this manner is converted to images and loses all
+information making it searchable and losing all compression. OCRmyPDF
+could be used restore searchability.
+
+How OCRmyPDF processes PDFs
+===========================
+
+OCRmyPDF must open and interpret your PDF in order to insert an OCR
+layer. First, it runs all PDFs through
+`pikepdf <https://github.com/pikepdf/pikepdf>`__, a library based on
+`qpdf <https://github.com/qpdf/qpdf>`__, a program that repairs PDFs
+with syntax errors. This is done because, in the author's experience, a
+significant number of PDFs in the wild especially those created by
+scanners are not well-formed files. qpdf makes it more likely that
+OCRmyPDF will succeed, but offers no security guarantees. qpdf is also
+used to split the PDF into single page PDFs.
+
+Finally, OCRmyPDF rasterizes each page of the PDF using
+`Ghostscript <http://ghostscript.com/>`__ in ``-dSAFER`` mode.
+
+Depending on the options specified, OCRmyPDF may graft the OCR layer
+into the existing PDF or it may essentially reconstruct ("re-fry") a
+visually identical PDF that may be quite different at the binary level.
+That said, OCRmyPDF is not a tool designed for sanitizing PDFs.
+
+.. _ocr-service:
+
+Using OCRmyPDF online or as a service
+=====================================
+
+OCRmyPDF is not designed for use as a public web service where a
+malicious user could upload a chosen PDF. In particular, it is not
+necessarily secure against PDF malware or PDFs that cause denial of
+service. OCRmyPDF relies on Ghostscript, and therefore, if deployed
+online one should be prepared to comply with Ghostscript's Affero GPL
+license, OCRmyPDF's GPL license, and any other licenses.
+
+Setting aside these concerns, a side effect of OCRmyPDF is it may
+incidentally sanitize PDFs that contain certain types of malware. It
+repairs the PDF with pikepdf/libqpdf, which could correct malformed PDF
+structures that are part of an attack. When PDF/A output is selected
+(the default), the input PDF is partially reconstructed by Ghostscript.
+When ``--force-ocr`` is used, all pages are rasterized and reconverted
+to PDF, which could remove malware in embedded images.
+
+OCRmyPDF should be relatively safe to use in a trusted intranet, with
+some considerations:
+
+Limiting CPU usage
+------------------
+
+OCRmyPDF will attempt to use all available CPUs and storage, so
+executing ``nice ocrmypdf`` or limiting the number of jobs with the
+``-j`` argument may ensure the server remains available. Another option
+would be run OCRmyPDF jobs inside a Docker container, a virtual machine,
+or a cloud instance, which can impose its own limits on CPU usage and be
+terminated "from orbit" if it fails to complete.
+
+Temporary storage requirements
+------------------------------
+
+OCRmyPDF will use a large amount of temporary storage for its work,
+proportional to the total number of pixels needed to rasterize the PDF.
+The raster image of a 8.5×11" color page at 300 DPI takes 25 MB
+uncompressed; OCRmyPDF saves its intermediates as PNG, but that still
+means it requires about 9 MB per intermediate based on average
+compression ratios. Multiple intermediates per page are also required,
+depending on the command line given. A rule of thumb would be to allow
+100 MB of temporary storage per page in a file – meaning that a small
+cloud servers or small VM partitions should be provisioned with plenty
+of extra space, if say, a 500 page file might be sent.
+
+To check temporary storage usage on actual files, run
+``ocrmypdf -k ...`` which will preserve and print the path to temporary
+storage when the job is done.
+
+To change where temporary files are stored, change the ``TMPDIR``
+environment variable for ocrmypdf's environment. (Python's
+``tempfile.gettempdir()`` returns the root directory in which temporary
+files will be stored.) For example, one could redirect ``TMPDIR`` to a
+large RAM disk to avoid wear on HDD/SSD and potentially improve
+performance. On Amazon Web Services, ``TMPDIR`` can be set to `empheral
+storage <https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html>`__.
+
+Timeouts
+--------
+
+To prevent excessively long OCR jobs consider setting
+``--tesseract-timeout`` and/or ``--skip-big`` arguments. ``--skip-big``
+is particularly helpful if your PDFs include documents such as reports
+on standard page sizes with large images attached - often large images
+are not worth OCR'ing anyway.
+
+Commercial alternatives
+-----------------------
+
+The author also provides professional services that include OCR and
+building databases around PDFs, and is happy to provide consultation.
+
+Abbyy Cloud OCR is a viable commercial alternative with a web services
+API.
+
+Password protection, digital signatures and certification
+=========================================================
+
+Password protected PDFs usually have two passwords, and owner and user
+password. When the user password is set to empty, PDF readers will open
+the file automatically and marked it as "(SECURED)". While not as
+reliable as a digital signature, this indicates that whoever set the
+password approved of the file at that time. When the user password is
+set, the document cannot be viewed without the password.
+
+Either way, OCRmyPDF does not remove passwords from PDFs and exits with
+an error on encountering them.
+
+``qpdf`` can remove passwords. If the owner and user password are set, a
+password is required for ``qpdf``. If only the owner password is set, then the
+password can be stripped, even if one does not have the owner password.
+
+After OCR is applied, password protection is not permitted on PDF/A
+documents but the file can be converted to regular PDF.
+
+Many programs exist which are capable of inserting an image of someone's
+signature. On its own, this offers no security guarantees. It is trivial
+to remove the signature image and apply it to other files. This practice
+offers no real security.
+
+Important documents can be digitally signed and certified to attest to
+their authorship. OCRmyPDF cannot do this. Open source tools such as
+pdfbox (Java) have this capability as does Adobe Acrobat.

docs/performance.rst

@@ -0,0 +1,22 @@
+===========
+Performance
+===========
+
+Some users have noticed that current versions of OCRmyPDF do not run as quickly
+as some older versions (specifically 6.x and older). This is because OCRmyPDF
+added image optimization as a postprocessing step, and it is enabled by default.
+
+Speed
+=====
+
+If running OCRmyPDF quickly is your main goal, you can use settings such as:
+
+* ``--optimize 0`` to disable file size optimization
+* ``--output-type pdf`` to disable PDF/A generation
+* ``--fast-web-view 0`` to disable fast web view optimization
+* ``--skip-big`` to skip large images, if some pages have large images
+
+You can also avoid:
+
+* ``--force-ocr``
+* Image preprocessing

docs/plugins.rst

@@ -0,0 +1,165 @@
+=======
+Plugins
+=======
+
+    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
+    NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and
+    "OPTIONAL" in this document are to be interpreted as described in
+    RFC 2119.
+
+You can use plugins to customize the behavior of OCRmyPDF at certain points of
+interest.
+
+Currently, it is possible to:
+
+- add new command line arguments
+- override the decision for whether or not to perform OCR on a particular file
+- modify the image is about to be sent for OCR
+- modify the page image before it is converted to PDF
+- replace the Tesseract OCR with another OCR engine that has similar behavior
+- replace Ghostscript with another PDF to image converter (rasterizer) or
+  PDF/A generator
+
+OCRmyPDF plugins are based on the Python ``pluggy`` package and conform to its
+conventions. Note that: plugins installed with as setuptools entrypoints are
+not checked currently, because OCRmyPDF assumes you may not want to enable
+plugins for all files.
+
+Script plugins
+==============
+
+Script plugins may be called from the command line, by specifying the name of a file.
+Script plugins may be convenient for informal or "one-off" plugins, when a certain
+batch of files needs a special processing step for example.
+
+.. code-block:: bash
+
+    ocrmypdf --plugin ocrmypdf_example_plugin.py input.pdf output.pdf
+
+Multiple plugins may be installed by issuing the ``--plugin`` argument multiple times.
+
+Packaged plugins
+================
+
+Installed plugins may be installed into the same virtual environment as OCRmyPDF
+is installed into. They may be invoked using Python standard module naming.
+If you are intending to distribute a plugin, please package it.
+
+.. code-block:: bash
+
+    ocrmypdf --plugin ocrmypdf_fancypants.pockets.contents input.pdf output.pdf
+
+OCRmyPDF does not automatically import plugins, because the assumption is that
+plugins affect different files differently and you may not want them activated
+all the time. The command line or ``ocrmypdf.ocr(plugin='...')`` must call
+for them.
+
+Third parties that wish to distribute packages for ocrmypdf should package them
+as packaged plugins, and these modules should begin with the name ``ocrmypdf_``
+similar to ``pytest`` packages such as ``pytest-cov`` (the package) and
+``pytest_cov`` (the module).
+
+.. note::
+
+    We strongly recommend plugin authors name their plugins with the prefix
+    ``ocrmypdf-`` (for the package name on PyPI) and ``ocrmypdf_`` (for the
+    module), just like pytest plugins.
+
+Plugin requirements
+===================
+
+OCRmyPDF generally uses multiple worker processes. When a new worker is started,
+Python will import all plugins again, including all plugins that were imported earlier.
+This means that the global state of a plugin in one worker will not be shared with
+other workers. As such, plugin hook implementations should be stateless, relying
+only on their inputs. Hook implementations may use their input parameters to
+to obtain a reference to shared state prepared by another hook implementation.
+Plugins must expect that other instances of the plugin will be running
+simultaneously.
+
+The ``context`` object that is passed to many hooks can be used to share information
+about a file being worked on. Plugins must write private, plugin-specific data to
+a subfolder named ``{options.work_folder}/ocrmypdf-plugin-name``. Plugins MAY
+read and write files in ``options.work_folder``, but should be aware that their
+semantics are subject to change.
+
+OCRmyPDF will delete ``options.work_folder`` when it has finished OCRing
+a file, unless invoked with ``--keep-temporary-files``.
+
+The documentation for some plugin hooks contain a detailed description of the
+execution context in which they will be called.
+
+Plugins should be prepared to work whether executed in worker threads or worker
+processes. Generally, OCRmyPDF uses processes, but has a semi-hidden threaded
+argument that simplifies debugging.
+
+
+Plugin hooks
+============
+
+A plugin may provide the following hooks. Hooks must be decorated with
+``ocrmypdf.hookimpl``, for example:
+
+.. code-block:: python
+
+    from ocrmpydf import hookimpl
+
+    @hookimpl
+    def add_options(parser):
+        pass
+
+The following is a complete list of hooks that are available, and when
+they are called.
+
+.. _firstresult:
+
+**Note on firstresult hooks**
+
+If multiple plugins install implementations for this hook, they will be called in
+the reverse of the order in which they are installed (i.e., last plugin wins).
+When each hook implementation is called in order, the first implementation that
+returns a value other than ``None`` will "win" and prevent execution of all other
+hooks. As such, you cannot "chain" a series of plugin filters together in this
+way. Instead, a single hook implementation should be responsible for any such
+chaining operations.
+
+Custom command line arguments
+-----------------------------
+
+.. autofunction:: ocrmypdf.pluginspec.add_options
+
+.. autofunction:: ocrmypdf.pluginspec.check_options
+
+Applying special behavior before processing
+-------------------------------------------
+
+.. autofunction:: ocrmypdf.pluginspec.validate
+
+PDF page to image
+-----------------
+
+.. autofunction:: ocrmypdf.pluginspec.rasterize_pdf_page
+
+Modifying intermediate images
+-----------------------------
+
+.. autofunction:: ocrmypdf.pluginspec.filter_ocr_image
+
+.. autofunction:: ocrmypdf.pluginspec.filter_page_image
+
+OCR engine
+----------
+
+.. autofunction:: ocrmypdf.pluginspec.get_ocr_engine
+
+.. autoclass:: ocrmypdf.pluginspec.OcrEngine
+    :members:
+
+    .. automethod:: __str__
+
+.. autoclass:: ocrmypdf.pluginspec.OrientationConfidence
+
+PDF/A production
+----------------
+
+.. autofunction:: ocrmypdf.pluginspec.generate_pdfa

docs/security.rst

@@ -1,79 +0,0 @@
-PDF security issues
-===================
-
-	OCRmyPDF should only be used on PDFs you trust. It is not designed to protect you against malware.
-
-Recognizing that many users have an interest in handling PDFs and applying OCR to PDFs they did not generate themselves, this article discusses the security implications of PDFs and how users can protect themselves.
-
-The disclaimer applies: this software has no warranties of any kind.
-
-PDFs may contain malware
-------------------------
-
-PDF is a rich, complex file format. The official PDF 1.7 specification, ISO 32000:2008, is hundreds of pages long and references several annexes each of which are similar in length. PDFs can contain video, audio, XML, JavaScript and other programming, and forms. In some cases, they can open internet connections to pre-selected URLs. All of these possible attack vectors.
-
-In short, PDFs `may contain viruses <https://security.stackexchange.com/questions/64052/can-a-pdf-file-contain-a-virus>`_.
-
-This `article <https://theinvisiblethings.blogspot.ca/2013/02/converting-untrusted-pdfs-into-trusted.html>`_ describes a high-paranoia method which allows potentially hostile PDFs to be viewed and rasterized safely in a disposable virtual machine. A trusted PDF created in this manner is converted to images and loses all information making it searchable and losing all compression. OCRmyPDF could be used restore searchability.
-
-How OCRmyPDF processes PDFs
----------------------------
-
-OCRmyPDF must open and interpret your PDF in order to insert an OCR layer. First, it runs all PDFs through `pikepdf <https://github.com/pikepdf/pikepdf>`_, a library based on `qpdf <https://github.com/qpdf/qpdf>`_, a program that repairs PDFs with syntax errors. This is done because, in the author's experience, a significant number of PDFs in the wild especially those created by scanners are not well-formed files. qpdf makes it more likely that OCRmyPDF will succeed, but offers no security guarantees. qpdf is also used to split the PDF into single page PDFs.
-
-Finally, OCRmyPDF rasterizes each page of the PDF using `Ghostscript <http://ghostscript.com/>`_ in ``-dSAFER`` mode.
-
-Depending on the options specified, OCRmyPDF may graft the OCR layer into the existing PDF or it may essentially reconstruct ("re-fry") a visually identical PDF that may be quite different at the binary level. That said, OCRmyPDF is not a tool designed for sanitizing PDFs.
-
-.. _ocr-service:
-
-Using OCRmyPDF online or as a service
--------------------------------------
-
-OCRmyPDF is not designed for use as a public web service where a malicious user could upload a chosen PDF. In particular, it is not necessarily secure against PDF malware or PDFs that cause denial of service. OCRmyPDF relies on Ghostscript, and therefore, if deployed online one should be prepared to comply with Ghostscript's Affero GPL license, OCRmyPDF's GPL license, and any other licenses.
-
-Setting aside these concerns, a side effect of OCRmyPDF is it may incidentally sanitize PDFs that contain certain types of malware. It runs ``qpdf`` to repair the PDF, which could correct malformed PDF structures that are part of an attack. When PDF/A output is selected (the default), the input PDF is partially reconstructed by Ghostscript. When ``--force-ocr`` is used, all pages are rasterized and reconverted to PDF, which could remove malware in embedded images.
-
-OCRmyPDF should be relatively safe to use in a trusted intranet, with some considerations:
-
-Limiting CPU usage
-^^^^^^^^^^^^^^^^^^
-
-OCRmyPDF will attempt to use all available CPUs and storage, so executing ``nice ocrmypdf`` or limiting the number of jobs with the ``-j`` argument may ensure the server remains available. Another option would be run OCRmyPDF jobs inside a Docker container, a virtual machine, or a cloud instance, which can impose its own limits on CPU usage and be terminated "from orbit" if it fails to complete.
-
-Temporary storage requirements
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-OCRmyPDF will use a large amount of temporary storage for its work, proportional to the total number of pixels needed to rasterize the PDF. The raster image of a 8.5×11" color page at 300 DPI takes 25 MB uncompressed; OCRmyPDF saves its intermediates as PNG, but that still means it requires about 9 MB per intermediate based on average compression ratios. Multiple intermediates per page are also required, depending on the command line given. A rule of thumb would be to allow 100 MB of temporary storage per page in a file – meaning that a small cloud servers or small VM partitions should be provisioned with plenty of extra space, if say, a 500 page file might be sent.
-
-To check temporary storage usage on actual files, run ``ocrmypdf -k ...`` which will preserve and print the path to temporary storage when the job is done.
-
-To change where temporary files are stored, change the ``TMPDIR`` environment variable for ocrmypdf's environment. (Python's ``tempfile.gettempdir()`` returns the root directory in which temporary files will be stored.) For example, one could redirect ``TMPDIR`` to a large RAM disk to avoid wear on HDD/SSD and potentially improve performance. On Amazon Web Services, ``TMPDIR`` can be set to `empheral storage <https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html>`_.
-
-Timeouts
-^^^^^^^^
-
-To prevent excessively long OCR jobs consider setting ``--tesseract-timeout`` and/or ``--skip-big`` arguments. ``--skip-big`` is particularly helpful if your PDFs include documents such as reports on standard page sizes with large images attached - often large images are not worth OCR'ing anyway.
-
-Commercial alternatives
-^^^^^^^^^^^^^^^^^^^^^^^
-
-The author also provides professional services that include OCR and building databases around PDFs, and is happy to provide consultation.
-
-Abbyy Cloud OCR is a viable commercial alternative with a web services API.
-
-
-Password protection, digital signatures and certification
----------------------------------------------------------
-
-Password protected PDFs usually have two passwords, and owner and user password. When the user password is set to empty, PDF readers will open the file automatically and marked it as "(SECURED)". While not as reliable as a digital signature, this indicates that whoever set the password approved of the file at that time. When the user password is set, the document cannot be viewed without the password.
-
-Either way, OCRmyPDF does not remove passwords from PDFs and exits with an error on encountering them.
-
-``qpdf``, one of OCRmyPDF's dependencies, can remove passwords. If the owner and user password are set, a password is required for ``qpdf``. If only the owner password is set, then the password can be stripped, even if one does not have the owner password.
-
-After OCR is applied, password protection is not permitted on PDF/A documents but the file can be converted to regular PDF.
-
-Many programs exist which are capable of inserting an image of someone's signature. On its own, this offers no security guarantees. It is trivial to remove the signature image and apply it to other files. This practice offers no real security.
-
-Important documents can be digitally signed and certified to attest to their authorship. OCRmyPDF cannot do this. Open source tools such as pdfbox (Java) have this capability as does Adobe Acrobat.

misc/batch.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+# Original version by DeliciousPickle@github; modified
+
+# This script must be edited to meet your needs.
+
+import logging
+import os
+import sys
+
+import ocrmypdf
+
+# pylint: disable=logging-format-interpolation
+# pylint: disable=logging-not-lazy
+
+script_dir = os.path.dirname(os.path.realpath(__file__))
+print(script_dir + '/batch.py: Start')
+
+if len(sys.argv) > 1:
+    start_dir = sys.argv[1]
+else:
+    start_dir = '.'
+
+if len(sys.argv) > 2:
+    log_file = sys.argv[2]
+else:
+    log_file = script_dir + '/ocr-tree.log'
+
+logging.basicConfig(
+    level=logging.INFO,
+    format='%(asctime)s %(message)s',
+    filename=log_file,
+    filemode='w',
+)
+
+ocrmypdf.configure_logging(ocrmypdf.Verbosity.default)
+
+for dir_name, subdirs, file_list in os.walk(start_dir):
+    logging.info(dir_name + '\n')
+    os.chdir(dir_name)
+    for filename in file_list:
+        file_ext = os.path.splitext(filename)[1]
+        if file_ext == '.pdf':
+            full_path = dir_name + '/' + filename
+            print(full_path)
+            result = ocrmypdf.ocr(filename, filename, deskew=True)
+            if result == ocrmypdf.ExitCode.already_done_ocr:
+                print("Skipped document because it already contained text")
+            elif result == ocrmypdf.ExitCode.ok:
+                print("OCR complete")
+            logging.info(result)

misc/completion/ocrmypdf.bash

@@ -0,0 +1,99 @@
+# ocrmypdf completion                                     -*- shell-script -*-
+
+set -o errexit
+
+_ocrmypdf()
+{
+    local cur prev cword words split
+
+    # Homebrew on Macs have version 1.3 of bash-completion which doesn't include - see #502
+    if declare -F _init_completions >/dev/null 2>&1; then
+        _init_completion -s || return
+    else
+        COMPREPLY=()
+        _get_comp_words_by_ref cur prev words cword
+    fi
+
+    if [[ $cur == -* ]]; then
+        COMPREPLY=( $( compgen -W '--language --image-dpi --output-type
+            --sidecar --version --jobs --quiet --verbose --title --author
+            --subject --keywords --rotate-pages --remove-background --deskew
+            --clean --clean-final --unpaper-args --oversample --remove-vectors
+            --threshold --force-ocr --skip-text --redo-ocr
+            --skip-big --jpeg-quality --png-quality --jbig2-lossy
+            --max-image-mpixels --tesseract-config --tesseract-pagesegmode
+            --help --tesseract-oem --pdf-renderer --tesseract-timeout
+            --rotate-pages-threshold --pdfa-image-compression --user-words
+            --user-patterns --keep-temporary-files --output-type
+            --no-progress-bar --pages --fast-web-view' \
+            --  "$cur" ) )
+        return
+    else
+        _filedir
+        return
+    fi
+
+    case $prev in
+        --version|-h|--help)
+            return
+            ;;
+        --user-words|--user-patterns|--tesseract-config)
+            _filedir
+            return
+            ;;
+        --output-type)
+            COMPREPLY=( $( compgen -W 'pdfa pdf pdfa-1 pdfa-2 pdfa-3' -- \
+                "$cur" ) )
+            return
+            ;;
+        --pdf-renderer)
+            COMPREPLY=( $( compgen -W 'auto hocr sandwich' -- "$cur" ) )
+            return
+            ;;
+        --pdfa-image-compression)
+            COMPREPLY=( $( compgen -W 'auto jpeg lossless' -- "$cur" ) )
+            return
+            ;;
+        -O|--optimize|--tesseract-oem)
+            COMPREPLY=( $( compgen -W '{0..3}' -- "$cur" ) )
+            return
+            ;;
+        --jpeg-quality|--png-quality)
+            COMPREPLY=( $( compgen -W '{0..100}' -- "$cur" ) )
+            return
+            ;;
+        -l|--language)
+            COMPREPLY=$( command tesseract --list-langs 2>/dev/null )
+            COMPREPLY=( $( compgen -W '${COMPREPLY[@]##*:}' -- "$cur" ) )
+            return
+            ;;
+        --image-dpi|--oversample|--skip-big|--max-image-mpixels|\
+        --tesseract-timeout|--rotate-pages-threshold)
+            COMPREPLY=( $( compgen -P "$cur" -W '{0..9}' ) )
+            return
+            ;;
+        -j|--jobs)
+            COMPREPLY=( $( compgen -W '{1..'$( _ncpus )'}' -- "$cur" ) )
+            return
+            ;;
+        -v|--verbose)
+            COMPREPLY=( $( compgen -W '{0..2}' -- "$cur" ) ) # max level ?
+            return
+            ;;
+        --tesseract-pagesegmode)
+            COMPREPLY=( $( compgen -W '{1..13}' -- "$cur" ) )
+            return
+            ;;
+        --sidecar|--title|--author|--subject|--keywords|--unpaper-args|--pages|--fast-web-view)
+            # argument required but no completions available
+            return
+            ;;
+    esac
+
+    $split && return
+} &&
+complete -F _ocrmypdf ocrmypdf
+
+set +o errexit
+
+# ex: filetype=sh

misc/completion/ocrmypdf.fish

@@ -0,0 +1,118 @@
+complete -c ocrmypdf -x -n '__fish_is_first_arg' -l version
+complete -c ocrmypdf -x -n '__fish_is_first_arg' -s h -s "?" -l help
+
+complete -c ocrmypdf -r -l sidecar -d "write OCR to text file"
+complete -c ocrmypdf -x -s q -l quiet
+
+complete -c ocrmypdf -s r -l rotate-pages -d "rotate pages to correct orientation"
+complete -c ocrmypdf -s d -l deskew -d "fix small horizontal alignment skew"
+complete -c ocrmypdf -s c -l clean -d "clean document images before OCR"
+complete -c ocrmypdf -s i -l clean-final -d "clean document images and keep result"
+complete -c ocrmypdf -l remove-vectors -d "don't send vector objects to OCR"
+complete -c ocrmypdf -l threshold -d "threshold images before OCR"
+
+complete -c ocrmypdf -s f -l force-ocr -d "OCR documents that already have printable text"
+complete -c ocrmypdf -s s -l skip-ocr -d "skip OCR on pages that text, otherwise try OCR"
+complete -c ocrmypdf -l redo-ocr -d "redo OCR on any pages that seem to have OCR already"
+
+complete -c ocrmypdf -s k -l keep-temporary-files -d "keep temporary files (debug)"
+
+function __fish_ocrmypdf_languages
+    set langs (tesseract --list-langs ^/dev/null)
+    set arr (string split '\n' $langs)
+    for lang in $arr[2..-1]
+        echo $lang
+    end
+end
+complete -c ocrmypdf -x -s l -l language -a '(__fish_ocrmypdf_languages)' -d "language"
+
+complete -c ocrmypdf -x -l image-dpi -d "assume this DPI if input image DPI is unknown"
+
+function __fish_ocrmypdf_output_type
+    echo -e "pdfa\t"(_ "output a PDF/A (default)")
+    echo -e "pdf\t"(_ "output a standard PDF")
+    echo -e "pdfa-1\t"(_ "output a PDF/A-1b")
+    echo -e "pdfa-2\t"(_ "output a PDF/A-2b")
+    echo -e "pdfa-3\t"(_ "output a PDF/A-3b")
+end
+complete -c ocrmypdf -x -l output-type -a '(__fish_ocrmypdf_output_type)' -d "select PDF output options"
+
+function __fish_ocrmypdf_pdf_renderer
+    echo -e "auto\t"(_ "auto select PDF renderer")
+    echo -e "hocr\t"(_ "use hocr renderer")
+    echo -e "sandwich\t"(_ "use sandwich renderer")
+end
+complete -c ocrmypdf -x -l pdf-renderer -a '(__fish_ocrmypdf_pdf_renderer)' -d "select PDF renderer options"
+
+function __fish_ocrmypdf_optimize
+    echo -e "0\t"(_ "do not optimize")
+    echo -e "1\t"(_ "do safe, lossless optimizations (default)")
+    echo -e "2\t"(_ "do some lossy optimizations")
+    echo -e "3\t"(_ "do aggressive lossy optimizations (including lossy JBIG2)")
+end
+complete -c ocrmypdf -x -s O -l optimize -a '(__fish_ocrmypdf_optimize)' -d "select optimization level"
+
+function __fish_ocrmypdf_verbose
+    echo -e "0\t"(_ "standard output messages")
+    echo -e "1\t"(_ "troubleshooting output messages")
+    echo -e "2\t"(_ "debugging output messages")
+end
+complete -c ocrmypdf -x -s v -l verbose -a '(__fish_ocrmypdf_verbose)' -d "set verbosity level"
+
+complete -c ocrmypdf -x -l no-progress-bar -d "disable the progress bar"
+
+function __fish_ocrmypdf_pdfa_compression
+    echo -e "auto\t"(_ "let Ghostscript decide how to compress images")
+    echo -e "jpeg\t"(_ "convert color and grayscale images to JPEG")
+    echo -e "lossless\t"(_ "convert color and grayscale images to lossless (PNG)")
+end
+complete -c ocrmypdf -x -l pdfa-image-compression -a '(__fish_ocrmypdf_pdfa_compression)' -d "set PDF/A image compression options"
+
+complete -c ocrmypdf -x -s j -l jobs -d "how many worker processes to use"
+complete -c ocrmypdf -x -l title -d "set metadata"
+complete -c ocrmypdf -x -l author -d "set metadata"
+complete -c ocrmypdf -x -l subject -d "set metadata"
+complete -c ocrmypdf -x -l keywords -d "set metadata"
+complete -c ocrmypdf -x -l oversample -d "oversample images to this DPI"
+complete -c ocrmypdf -x -l skip-big -d "skip OCR on pages larger than this many MPixels"
+
+complete -c ocrmypdf -x -l jpeg-quality -d "JPEG quality [0..100]"
+complete -c ocrmypdf -x -l png-quality -d "PNG quality [0..100]"
+complete -c ocrmypdf -x -l jbig2-lossy -d "enable lossy JBIG2 (see docs)"
+complete -c ocrmypdf -x -l max-image-mpixels -d "image decompression bomb threshold"
+complete -c ocrmypdf -x -l pages -d "apply OCR to only the specified pages"
+complete -c ocrmypdf -x -l tesseract-config -d "set custom tesseract config file"
+
+function __fish_ocrmypdf_tesseract_pagesegmode
+  echo -e "0\t"(_ "orientation and script detection (OSD) only")
+  echo -e "1\t"(_ "automatic page segmentation with OSD")
+  echo -e "2\t"(_ "automatic page segmentation, but no OSD, or OCR")
+  echo -e "3\t"(_ "fully automatic page segmentation, but no OSD (default)")
+  echo -e "4\t"(_ "assume a single column of text of variable sizes")
+  echo -e "5\t"(_ "assume a single uniform block of vertically aligned text")
+  echo -e "6\t"(_ "assume a single uniform block of text")
+  echo -e "7\t"(_ "treat the image as a single text line")
+  echo -e "8\t"(_ "treat the image as a single word")
+  echo -e "9\t"(_ "treat the image as a single word in a circle")
+  echo -e "10\t"(_ "treat the image as a single character")
+  echo -e "11\t"(_ "sparse text - find as much text as possible in no particular order")
+  echo -e "12\t"(_ "sparse text with OSD")
+  echo -e "13\t"(_ "raw line - treat the image as a single text line")
+end
+complete -c ocrmypdf -x -l tesseract-pagesegmode -a '(__fish_ocrmypdf_tesseract_pagesegmode)' -d "set tesseract --psm"
+
+function __fish_ocrmypdf_tesseract_oem
+    echo -e "0\t"(_ "legacy engine only")
+    echo -e "1\t"(_ "neural nets LSTM engine only")
+    echo -e "2\t"(_ "legacy + LSTM engines")
+    echo -e "3\t"(_ "default, based on what is available")
+end
+complete -c ocrmypdf -x -l tesseract-oem -a '(__fish_ocrmypdf_tesseract_oem)' -d "set tesseract --oem"
+complete -c ocrmypdf -x -l tesseract-timeout -d "maximum number of seconds to wait for OCR"
+complete -c ocrmypdf -x -l rotate-pages-threshold -d "page rotation confidence"
+
+complete -c ocrmypdf -r -l user-words -d "specify location of user words file"
+complete -c ocrmypdf -r -l user-patterns -d "specify location of user patterns file"
+complete -c ocrmypdf -x -l fast-web-view -d "if file size if above this amount in MB, linearize PDF"
+
+complete -c ocrmypdf -x -a "(__fish_complete_suffix .pdf)"

misc/completions.fish

@@ -1,70 +0,0 @@
-complete -c ocrmypdf -l version
-complete -c ocrmypdf -l help
-
-complete -c ocrmypdf -l sidecar -r -d "write OCR to text file"
-complete -c ocrmypdf -s q -l quiet
-
-complete -c ocrmypdf -s r -l rotate-pages -d "rotate pages to correct orientation"
-complete -c ocrmypdf -s d -l deskew -d "fix small horizontal alignment skew"
-complete -c ocrmypdf -s c -l clean -d "clean document images before OCR"
-complete -c ocrmypdf -s i -l clean-final -d "clean document images and keep result"
-complete -c ocrmypdf -l remove-vectors -d "don't send vector objects to OCR"
-complete -c ocrmypdf -l mask-barcodes -d "mask barcodes from OCR"
-complete -c ocrmypdf -l threshold -d "threshold images before OCR"
-
-complete -c ocrmypdf -s f -l force-ocr -d "OCR documents that already have printable text"
-complete -c ocrmypdf -s s -l skip-ocr -d "skip OCR on pages that text, otherwise try OCR"
-complete -c ocrmypdf -l redo-ocr -d "redo OCR on any pages that seem to have OCR already"
-
-complete -c ocrmypdf -s k -l keep-temporary-files -d "keep temporary files (debug)"
-
-complete -c ocrmypdf -x -s l -l language -d 'language'
-complete -c ocrmypdf -x -s l -l language -a '(tesseract --list-langs)'
-
-complete -c ocrmypdf -x -l image-dpi -d "assume this DPI if input image DPI is unknown"
-
-function __fish_ocrmypdf_output_type
-    echo -e "pdfa\t"(_ "output a PDF/A (default)")
-    echo -e "pdf\t"(_ "output a standard PDF")
-    echo -e "pdfa-1\t"(_ "output a PDF/A-1b")
-    echo -e "pdfa-2\t"(_ "output a PDF/A-2b")
-    echo -e "pdfa-3\t"(_ "output a PDF/A-3b")
-end
-complete -c ocrmypdf -x -l output-type -a '(__fish_ocrmypdf_output_type)' -d "select PDF output options"
-
-function __fish_ocrmypdf_pdf_renderer
-    echo -e "auto\t"(_ "auto select PDF renderer")
-    echo -e "hocr\t"(_ "use hocr renderer")
-    echo -e "sandwich\t"(_ "use sandwich renderer")
-end
-complete -c ocrmypdf -x -l pdf-render -a '(__fish_ocrmypdf_pdf_renderer)' -d "select PDF renderer options"
-
-function __fish_ocrmypdf_optimize
-    echo -e "0\t"(_ "do not optimize")
-    echo -e "1\t"(_ "do safe, lossless optimizations (default)")
-    echo -e "2\t"(_ "do some lossy optimizations")
-    echo -e "3\t"(_ "do aggressive lossy optimizations (including lossy JBIG2)")
-end
-complete -c ocrmypdf -x -s O -l optimize -a '(__fish_ocrmypdf_optimize)' -d "select optimization level"
-
-complete -c ocrmypdf -x -s j -l jobs -d "how many worker processes to use"
-complete -c ocrmypdf -x -s v -a '(seq 1 9)'
-complete -c ocrmypdf -x -l title -d "set metadata"
-complete -c ocrmypdf -x -l author -d "set metadata"
-complete -c ocrmypdf -x -l subject -d "set metadata"
-complete -c ocrmypdf -x -l keywords -d "set metadata"
-complete -c ocrmypdf -x -l oversample -d "oversample images to this DPI"
-complete -c ocrmypdf -x -l skip-big -d "skip OCR on pages larger than this many MPixels"
-
-complete -c ocrmypdf -x -l jpeg-quality -d "JPEG quality [0..100]"
-complete -c ocrmypdf -x -l png-quality -d "PNG quality [0..100]"
-complete -c ocrmypdf -x -l jbig2-lossy -d "enable lossy JBIG2 (see docs)"
-complete -c ocrmypdf -x -l max-image-mpixels -d "image decompression bomb threshold"
-complete -c ocrmypdf -x -l tesseract-config -d "set custom tesseract config file"
-complete -c ocrmypdf -x -l tesseract-pagesegmode -d "set tesseract --psm"
-complete -c ocrmypdf -x -l tesseract-oem -d "set tesseract --oem"
-complete -c ocrmypdf -x -l tesseract-timeout -d "maximum number of seconds to wait for OCR"
-complete -c ocrmypdf -x -l rotate-pages-threshold -d "page rotation confidence"
-complete -c ocrmypdf -x -l pdfa-image-compression -a 'auto jpeg lossless' -d "set PDF/A image compression options"
-
-complete -c ocrmypdf -x -a "(__fish_complete_suffix .pdf)"

misc/docker-compose.example.yml

@@ -0,0 +1,15 @@
+---
+version: "3.3"
+services:
+  ocrmypdf:
+    restart: always
+    container_name: ocrmypdf
+    image: jbarlow83/ocrmypdf
+    volumes:
+      - "/media/scan:/input"
+      - "/mnt/scan:/output"
+    environment:
+      - OCR_OUTPUT_DIRECTORY_YEAR_MONT=0
+    user: "<SET TO YOUR USER ID>:<SET TO YOUR GROUP ID>"
+    entrypoint: python3
+    command: watcher.py

misc/example_plugin.py

@@ -0,0 +1,53 @@
+# © 2020 James R Barlow: https://github.com/jbarlow83
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+
+from PIL import Image
+
+from ocrmypdf import hookimpl
+
+log = logging.getLogger(__name__)
+
+
+@hookimpl
+def add_options(parser):
+    parser.add_argument('--grayscale-ocr', action='store_true')
+
+
+@hookimpl
+def prepare(options):
+    pass
+
+
+@hookimpl
+def validate(pdfinfo, options):
+    pass
+
+
+@hookimpl
+def filter_ocr_image(page, image):
+    if page.options.grayscale_ocr:
+        log.info("graying")
+        return image.convert('L')
+    return image
+
+
+@hookimpl
+def filter_page_image(page, image_filename):
+    output = image_filename.with_suffix('.jpg')
+    with Image.open(image_filename) as im:
+        im.save(output)
+    return output

misc/synology.py

@@ -0,0 +1,72 @@
+#!/bin/env python3
+# Contributed by github.com/Enantiomerie
+
+# This script must be edited to meet your needs.
+
+import logging
+import os
+import shutil
+import subprocess
+import sys
+import time
+
+# pylint: disable=logging-format-interpolation
+# pylint: disable=logging-not-lazy
+
+script_dir = os.path.dirname(os.path.realpath(__file__))
+timestamp = time.strftime("%Y-%m-%d-%H%M_")
+log_file = script_dir + '/' + timestamp + 'ocrmypdf.log'
+logging.basicConfig(
+    level=logging.INFO,
+    format='%(asctime)s %(message)s',
+    filename=log_file,
+    filemode='w',
+)
+
+if len(sys.argv) > 1:
+    start_dir = sys.argv[1]
+else:
+    start_dir = '.'
+
+for dir_name, subdirs, file_list in os.walk(start_dir):
+    logging.info(dir_name)
+    os.chdir(dir_name)
+    for filename in file_list:
+        file_stem, file_ext = os.path.splitext(filename)
+        if file_ext != '.pdf':
+            continue
+        full_path = os.path.join(dir_name, filename)
+        timestamp_ocr = time.strftime("%Y-%m-%d-%H%M_OCR_")
+        filename_ocr = timestamp_ocr + file_stem + '.pdf'
+        # create string for pdf processing
+        # the script is processed as root user via chron
+        cmd = [
+            'docker',
+            'run',
+            '--rm',
+            '-i',
+            'jbarlow83/ocrmypdf',
+            '--deskew',
+            '-',
+            '-',
+        ]
+        logging.info(cmd)
+        full_path_ocr = os.path.join(dir_name, filename_ocr)
+        with open(filename, 'rb') as input_file, open(
+            full_path_ocr, 'wb'
+        ) as output_file:
+            proc = subprocess.run(
+                cmd,
+                stdin=input_file,
+                stdout=output_file,
+                stderr=subprocess.PIPE,
+                check=False,
+            )
+        logging.info(proc.stderr.read())
+        os.chmod(full_path_ocr, 0o664)
+        os.chmod(full_path, 0o664)
+        full_path_ocr_archive = sys.argv[2]
+        full_path_archive = sys.argv[2] + '/no_ocr'
+        shutil.move(full_path_ocr, full_path_ocr_archive)
+        shutil.move(full_path, full_path_archive)
+logging.info('Finished.\n')

misc/watcher.py

@@ -0,0 +1,156 @@
+# Copyright (C) 2019 Ian Alexander: https://github.com/ianalexander
+# Copyright (C) 2020 James R Barlow: https://github.com/jbarlow83
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import json
+import logging
+import os
+import sys
+import time
+from datetime import datetime
+from pathlib import Path
+
+import pikepdf
+from watchdog.events import PatternMatchingEventHandler
+from watchdog.observers import Observer
+from watchdog.observers.polling import PollingObserver
+
+import ocrmypdf
+
+# pylint: disable=logging-format-interpolation
+
+INPUT_DIRECTORY = os.getenv('OCR_INPUT_DIRECTORY', '/input')
+OUTPUT_DIRECTORY = os.getenv('OCR_OUTPUT_DIRECTORY', '/output')
+OUTPUT_DIRECTORY_YEAR_MONTH = bool(os.getenv('OCR_OUTPUT_DIRECTORY_YEAR_MONTH', ''))
+ON_SUCCESS_DELETE = bool(os.getenv('OCR_ON_SUCCESS_DELETE', ''))
+DESKEW = bool(os.getenv('OCR_DESKEW', ''))
+OCR_JSON_SETTINGS = json.loads(os.getenv('OCR_JSON_SETTINGS', '{}'))
+POLL_NEW_FILE_SECONDS = int(os.getenv('OCR_POLL_NEW_FILE_SECONDS', '1'))
+USE_POLLING = bool(os.getenv('OCR_USE_POLLING', ''))
+LOGLEVEL = os.getenv('OCR_LOGLEVEL', 'INFO').upper()
+PATTERNS = ['*.pdf']
+
+log = logging.getLogger('ocrmypdf-watcher')
+
+
+def get_output_dir(root, basename):
+    if OUTPUT_DIRECTORY_YEAR_MONTH:
+        today = datetime.today()
+        output_directory_year_month = (
+            Path(root) / str(today.year) / f'{today.month:02d}'
+        )
+        if not output_directory_year_month.exists():
+            output_directory_year_month.mkdir(parents=True, exist_ok=True)
+        output_path = Path(output_directory_year_month) / basename
+    else:
+        output_path = Path(OUTPUT_DIRECTORY) / basename
+    return output_path
+
+
+def wait_for_file_ready(file_path):
+    # This loop waits to make sure that the file is completely loaded on
+    # disk before attempting to read. Docker sometimes will publish the
+    # watchdog event before the file is actually fully on disk, causing
+    # pikepdf to fail.
+
+    retries = 5
+    while retries:
+        try:
+            pdf = pikepdf.open(file_path)
+        except (FileNotFoundError, pikepdf.PdfError) as e:
+            log.info(f"File {file_path} is not ready yet")
+            log.debug("Exception was", exc_info=e)
+            time.sleep(POLL_NEW_FILE_SECONDS)
+            retries -= 1
+        else:
+            pdf.close()
+            return True
+
+    return False
+
+
+def execute_ocrmypdf(file_path):
+    file_path = Path(file_path)
+    output_path = get_output_dir(OUTPUT_DIRECTORY, file_path.name)
+
+    log.info("-" * 20)
+    log.info(f'New file: {file_path}. Waiting until fully loaded...')
+    if not wait_for_file_ready(file_path):
+        log.info(f"Gave up waiting for {file_path} to become ready")
+        return
+    log.info(f'Attempting to OCRmyPDF to: {output_path}')
+    exit_code = ocrmypdf.ocr(
+        input_file=file_path,
+        output_file=output_path,
+        deskew=DESKEW,
+        **OCR_JSON_SETTINGS,
+    )
+    if exit_code == 0 and ON_SUCCESS_DELETE:
+        log.info(f'OCR is done. Deleting: {file_path}')
+        file_path.unlink()
+    else:
+        log.info('OCR is done')
+
+
+class HandleObserverEvent(PatternMatchingEventHandler):
+    def on_any_event(self, event):
+        if event.event_type in ['created']:
+            execute_ocrmypdf(event.src_path)
+
+
+def main():
+    ocrmypdf.configure_logging(
+        verbosity=ocrmypdf.Verbosity.default, manage_root_logger=True
+    )
+    log.setLevel(LOGLEVEL)
+    log.info(
+        f"Starting OCRmyPDF watcher with config:\n"
+        f"Input Directory: {INPUT_DIRECTORY}\n"
+        f"Output Directory: {OUTPUT_DIRECTORY}\n"
+        f"Output Directory Year & Month: {OUTPUT_DIRECTORY_YEAR_MONTH}"
+    )
+    log.debug(
+        f"INPUT_DIRECTORY: {INPUT_DIRECTORY}\n"
+        f"OUTPUT_DIRECTORY: {OUTPUT_DIRECTORY}\n"
+        f"OUTPUT_DIRECTORY_YEAR_MONTH: {OUTPUT_DIRECTORY_YEAR_MONTH}\n"
+        f"ON_SUCCESS_DELETE: {ON_SUCCESS_DELETE}\n"
+        f"DESKEW: {DESKEW}\n"
+        f"ARGS: {OCR_JSON_SETTINGS}\n"
+        f"POLL_NEW_FILE_SECONDS: {POLL_NEW_FILE_SECONDS}\n"
+        f"USE_POLLING: {USE_POLLING}\n"
+        f"LOGLEVEL: {LOGLEVEL}\n"
+    )
+
+    if 'input_file' in OCR_JSON_SETTINGS or 'output_file' in OCR_JSON_SETTINGS:
+        log.error('OCR_JSON_SETTINGS should not specify input file or output file')
+        sys.exit(1)
+
+    handler = HandleObserverEvent(patterns=PATTERNS)
+    if USE_POLLING:
+        observer = PollingObserver()
+    else:
+        observer = Observer()
+    observer.schedule(handler, INPUT_DIRECTORY, recursive=True)
+    observer.start()
+    try:
+        while True:
+            time.sleep(1)
+    except KeyboardInterrupt:
+        observer.stop()
+    observer.join()
+
+
+if __name__ == "__main__":
+    main()

misc/webservice.py

@@ -23,21 +23,22 @@ to emphasize that SaaS deployments should make sure they comply with
 Ghostscript's license as well as OCRmyPDF's.
 """
 
+import os
+import shlex
+from subprocess import PIPE, run
+from tempfile import TemporaryDirectory
+
 from flask import (
     Flask,
     Response,
-    flash,
-    request,
-    redirect,
-    url_for,
     abort,
+    flash,
+    redirect,
+    request,
     send_from_directory,
+    url_for,
 )
-from subprocess import run, PIPE
-from tempfile import TemporaryDirectory
 from werkzeug.utils import secure_filename
-import os
-import shlex
 
 app = Flask(__name__)
 app.secret_key = "secret"

pyproject.toml

@@ -10,7 +10,7 @@ build-backend = "setuptools.build_meta"
 
 [tool.black]
 line-length = 88
-py36 = true
+target-version = ["py36", "py37", "py38"]
 skip-string-normalization = true
 include = '\.pyi?$'
 exclude = '''
@@ -28,5 +28,6 @@ exclude = '''
   | docs
   | misc
   | \.egg-info
+  | src/ocrmypdf/lib/_leptonica.py
 )/
 '''

requirements/dev.txt

@@ -1,4 +0,0 @@
-check-manifest >= 0.35
-twine >= 1.8.1
-coverage >= 4.5
-GitPython == 2.1.3

requirements/main.txt

@@ -1,13 +1,12 @@
 # requirements.txt can be used to replicate the developer's build environment
 # setup.py lists a separate set of requirements that are looser to simplify
 # installation
-chardet == 3.0.4
-cffi == 1.12.2
-img2pdf == 0.3.3
-pdfminer.six == 20181108
-pikepdf == 1.1.0
-Pillow >= 5.0.0, != 5.1.0 ; sys_platform == "darwin"
-pycparser == 2.19
-python-xmp-toolkit == 2.0.1
-reportlab == 3.5.13
-ruffus == 2.8.1
+cffi == 1.14.0
+coloredlogs == 14.0  # technically optional
+img2pdf == 0.3.6
+pdfminer.six == 20200517
+pikepdf == 1.16.1
+pluggy == 0.13.1
+Pillow == 7.1.2
+reportlab == 3.5.42
+tqdm == 4.46.1

requirements/test.txt

@@ -1,8 +1,7 @@
-pytest == 4.3.0
+pytest >= 5.0.0
 pytest-helpers-namespace >= 2019.1.8
-pytest-xdist
-pytest-cov >= 2.6.1
-python-xmp-toolkit   # requires apt-get install libexempi3
+pytest-xdist >= 1.31.0
+pytest-cov >= 2.10.0
+python-xmp-toolkit == 2.0.1  # requires apt-get install libexempi3
                      # or brew install exempi
-PyPDF2 >= 1.26.0
 #PyMuPDF == 1.13.4    # optional

requirements/watcher.txt

@@ -0,0 +1 @@
+watchdog == 0.10.2

requirements/webservice.txt

@@ -0,0 +1 @@
+Flask >= 1, < 2

setup.cfg

@@ -13,6 +13,8 @@ norecursedirs = lib .pc .git output cache resources
 testpaths = tests
 filterwarnings =
 	ignore:.*XMLParser.*:DeprecationWarning
+markers =
+	slow
 
 [isort]
 multi_line_output=3
@@ -20,6 +22,8 @@ include_trailing_comma=True
 force_grid_wrap=0
 use_parentheses=True
 line_length=88
+known_first_party = ocrmypdf
+known_third_party = PIL,_cffi_backend,cffi,flask,img2pdf,pdfminer,pikepdf,pkg_resources,pluggy,pytest,reportlab,setuptools,sphinx_rtd_theme,tqdm,watchdog,werkzeug
 
 [metadata]
 license_file = LICENSE

setup.py

@@ -21,30 +21,12 @@ from __future__ import print_function, unicode_literals
 
 import sys
 
+from setuptools import find_packages, setup
+
 if sys.version_info < (3, 6):
     print("Python 3.6 or newer is required", file=sys.stderr)
     sys.exit(1)
 
-from setuptools import setup, find_packages
-from subprocess import STDOUT, check_output, CalledProcessError
-from collections.abc import Mapping
-import re
-
-# pylint: disable=w0613
-
-
-command = next((arg for arg in sys.argv[1:] if not arg.startswith('-')), '')
-if command.startswith('install') or command in [
-    'check',
-    'test',
-    'nosetests',
-    'easy_install',
-]:
-    forced = '--force' in sys.argv
-    if forced:
-        print("The argument --force is deprecated. Please discontinue use.")
-
-
 if 'upload' in sys.argv[1:]:
     print('Use twine to upload the package - setup.py upload is insecure')
     sys.exit(1)
@@ -64,13 +46,15 @@ setup(
     long_description_content_type='text/markdown',
     url='https://github.com/jbarlow83/OCRmyPDF',
     author='James R. Barlow',
-    author_email='jim@purplerock.ca',
+    author_email='james@purplerock.ca',
     packages=find_packages('src', exclude=["tests", "tests.*"]),
     package_dir={'': 'src'},
     keywords=['PDF', 'OCR', 'optical character recognition', 'PDF/A', 'scanning'],
     classifiers=[
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "Development Status :: 5 - Production/Stable",
         "Environment :: Console",
         "Intended Audience :: End Users/Desktop",
@@ -78,6 +62,7 @@ setup(
         "Intended Audience :: System Administrators",
         "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
         "Operating System :: MacOS :: MacOS X",
+        "Operating System :: Microsoft :: Windows :: Windows 10",
         "Operating System :: POSIX",
         "Operating System :: POSIX :: BSD",
         "Operating System :: POSIX :: Linux",
@@ -95,20 +80,18 @@ setup(
     use_scm_version={'version_scheme': 'post-release'},
     cffi_modules=['src/ocrmypdf/lib/compile_leptonica.py:ffibuilder'],
     install_requires=[
-        'chardet >= 3.0.4, < 4',  # unlisted requirement of pdfminer.six 20181108
         'cffi >= 1.9.1',  # must be a setup and install requirement
+        'coloredlogs >= 14.0',  # strictly optional
         'img2pdf >= 0.3.0, < 0.4',  # pure Python, so track HEAD closely
-        'pdfminer.six == 20181108 ; sys_platform != "darwin"',
-        'pikepdf >= 1.1.0, < 2',
-        'Pillow >= 4.0.0, != 5.1.0 ; sys_platform == "darwin"',
-        # Pillow < 4 has BytesIO/TIFF bug w/img2pdf 0.2.3
-        # block 5.1.0, broken wheels
+        'pdfminer.six >= 20191110, <= 20200726',
+        'pikepdf >= 1.14.0, < 2',
+        'Pillow >= 7.0.0',
+        'pluggy >= 0.13.0',
         'reportlab >= 3.3.0',  # oldest released version with sane image handling
-        'ruffus >= 2.7.0',
+        'tqdm >= 4',
     ],
-    extras_require={'pdfminer': ['pdfminer.six == 20181108']},
     tests_require=tests_require,
-    entry_points={'console_scripts': ['ocrmypdf = ocrmypdf.__main__:run_pipeline']},
+    entry_points={'console_scripts': ['ocrmypdf = ocrmypdf.__main__:run']},
     package_data={'ocrmypdf': ['data/sRGB.icc']},
     include_package_data=True,
     zip_safe=False,

src/ocrmypdf/__init__.py

@@ -15,32 +15,27 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
-import pkg_resources
 
-PROGRAM_NAME = 'ocrmypdf'
+from pluggy import HookimplMarker as _HookimplMarker
 
-# Official PEP 396
-__version__ = pkg_resources.get_distribution('ocrmypdf').version
-
-VERSION = __version__
-
-from .exceptions import (
-    ExitCode,
+from ocrmypdf import helpers, hocrtransform, leptonica, pdfa, pdfinfo
+from ocrmypdf._version import PROGRAM_NAME, __version__
+from ocrmypdf.api import Verbosity, configure_logging, ocr
+from ocrmypdf.exceptions import (
     BadArgsError,
-    PdfMergeFailedError,
-    MissingDependencyError,
-    UnsupportedImageFormatError,
     DpiError,
-    OutputFileAccessError,
-    PriorOcrFoundError,
-    InputFileError,
-    SubprocessOutputError,
     EncryptedPdfError,
+    ExitCode,
+    ExitCodeException,
+    InputFileError,
+    MissingDependencyError,
+    OutputFileAccessError,
+    PdfMergeFailedError,
+    PriorOcrFoundError,
+    SubprocessOutputError,
     TesseractConfigError,
+    UnsupportedImageFormatError,
 )
+from ocrmypdf.pluginspec import OcrEngine, OrientationConfidence
 
-from . import helpers
-from . import hocrtransform
-from . import leptonica
-from . import pdfa
-from . import pdfinfo
+hookimpl = _HookimplMarker('ocrmypdf')

src/ocrmypdf/_concurrent.py

@@ -0,0 +1,148 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+import logging.handlers
+import multiprocessing
+import os
+import signal
+import sys
+import threading
+from multiprocessing import Pool as ProcessPool
+from multiprocessing.dummy import Pool as ThreadPool
+from typing import Callable, Iterable, Optional
+
+from tqdm import tqdm
+
+from ocrmypdf.exceptions import InputFileError
+
+
+def log_listener(queue):
+    """Listen to the worker processes and forward the messages to logging
+
+    For simplicity this is a thread rather than a process. Only one process
+    should actually write to sys.stderr or whatever we're using, so if this is
+    made into a process the main application needs to be directed to it.
+
+    See https://docs.python.org/3/howto/logging-cookbook.html#logging-to-a-single-file-from-multiple-processes
+    """
+
+    while True:
+        try:
+            record = queue.get()
+            if record is None:
+                break
+            logger = logging.getLogger(record.name)
+            logger.handle(record)
+        except Exception:  # pylint: disable=broad-except
+            import traceback  # pylint: disable=import-outside-toplevel
+
+            print("Logging problem", file=sys.stderr)
+            traceback.print_exc(file=sys.stderr)
+
+
+def process_sigbus(*args):
+    raise InputFileError("A worker process lost access to an input file")
+
+
+def process_init(queue, user_init):
+    """Initialize a process pool worker"""
+
+    # Ignore SIGINT (our parent process will kill us gracefully)
+    signal.signal(signal.SIGINT, signal.SIG_IGN)
+
+    # Install SIGBUS handler (so our parent process can abort somewhat gracefully)
+    if hasattr(signal, 'SIGBUS'):
+        signal.signal(signal.SIGBUS, process_sigbus)
+
+    # Reconfigure the root logger for this process to send all messages to a queue
+    h = logging.handlers.QueueHandler(queue)
+    root = logging.getLogger()
+    root.handlers = []
+    root.addHandler(h)
+
+    if user_init:
+        user_init()
+
+
+def thread_init(_queue, user_init):
+    # As a thread, block SIGBUS so the main thread deals with it...
+    if hasattr(signal, 'SIGBUS'):
+        signal.pthread_sigmask(signal.SIG_BLOCK, {signal.SIGBUS})
+    if user_init:
+        user_init()
+
+
+def exec_progress_pool(
+    *,
+    use_threads: bool,
+    max_workers: int,
+    tqdm_kwargs: dict,
+    task_initializer: Optional[Callable] = None,
+    task: Optional[Callable] = None,
+    task_arguments: Optional[Iterable] = None,
+    task_finished: Optional[Callable] = None,
+):
+    log_queue: multiprocessing.Queue = multiprocessing.Queue(-1)
+    listener = threading.Thread(target=log_listener, args=(log_queue,))
+
+    if use_threads:
+        pool_class = ThreadPool
+        initializer = thread_init
+    else:
+        pool_class = ProcessPool
+        initializer = process_init
+    listener.start()
+
+    with tqdm(**tqdm_kwargs) as pbar:
+        pool = pool_class(
+            processes=max_workers,
+            initializer=initializer,
+            initargs=(log_queue, task_initializer),
+        )
+        try:
+            results = pool.imap_unordered(task, task_arguments)
+            while True:
+                try:
+                    result = results.next()
+                    if task_finished:
+                        task_finished(result, pbar)
+                    else:
+                        pbar.update()
+                except StopIteration:
+                    break
+        except KeyboardInterrupt:
+            # Terminate pool so we exit instantly
+            pool.terminate()
+            # Don't try listener.join() here, will deadlock
+            raise
+        except Exception:
+            if not os.environ.get("PYTEST_CURRENT_TEST", ""):
+                # Unless inside pytest, exit immediately because no one wants
+                # to wait for child processes to finalize results that will be
+                # thrown away. Inside pytest, we want child processes to exit
+                # cleanly so that they output an error messages or coverage data
+                # we need from them.
+                pool.terminate()
+            raise
+        finally:
+            # Terminate log listener
+            log_queue.put_nowait(None)
+            pool.close()
+            pool.join()
+
+    listener.join()

src/ocrmypdf/_exec/__init__.py

@@ -0,0 +1,18 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Manage third party executables"""

src/ocrmypdf/_exec/ghostscript.py

@@ -0,0 +1,248 @@
+# © 2017 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Interface to Ghostscript executable"""
+
+import logging
+import os
+import re
+from io import BytesIO
+from os import fspath
+from pathlib import Path
+from shutil import which
+from subprocess import PIPE, CalledProcessError
+from typing import Optional, cast
+
+from PIL import Image
+
+from ocrmypdf.exceptions import MissingDependencyError, SubprocessOutputError
+from ocrmypdf.helpers import Resolution
+from ocrmypdf.subprocess import get_version, run
+
+log = logging.getLogger(__name__)
+
+_gswin = None
+if os.name == 'nt':
+    _gswin = which('gswin64c')
+    if not _gswin:
+        _gswin = which('gswin32c')
+        if not _gswin:
+            raise MissingDependencyError(
+                """
+                ---------------------------------------------------------------------
+                This error normally occurs when ocrmypdf can't Ghostscript.  Please
+                ensure Ghostscript is installed and its location is added to the
+                system PATH environment variable.
+
+                For details see:
+                    https://ocrmypdf.readthedocs.io/en/latest/installation.html
+                ---------------------------------------------------------------------
+                """
+            )
+    _gswin = Path(_gswin).stem
+
+GS = _gswin if _gswin else 'gs'
+del _gswin
+
+
+def version():
+    return get_version(GS)
+
+
+def jpeg_passthrough_available() -> bool:
+    """Returns True if the installed version of Ghostscript supports JPEG passthru
+
+    Prior to 9.23, Ghostscript decode and re-encoded JPEGs internally. In 9.23
+    it gained the ability to keep JPEGs unmodified. However, the 9.23
+    implementation was buggy and would deletes the last two bytes of images in
+    some cases, as reported here.
+    https://bugs.ghostscript.com/show_bug.cgi?id=699216
+
+    The issue was fixed for 9.24, hence that is the first version we consider
+    the feature available. (However, we don't use 9.24 at all, so the first
+    version that allows JPEG passthrough is 9.25.
+
+    """
+    return version() >= '9.24'
+
+
+def _gs_error_reported(stream) -> bool:
+    return True if re.search(r'error', stream, flags=re.IGNORECASE) else False
+
+
+def rasterize_pdf(
+    input_file: os.PathLike,
+    output_file: os.PathLike,
+    *,
+    raster_device: str,
+    raster_dpi: Resolution,
+    pageno: int = 1,
+    page_dpi: Resolution = None,
+    rotation: int = None,
+    filter_vector: bool = False,
+):
+    """Rasterize one page of a PDF at resolution raster_dpi in canvas units."""
+    raster_dpi = raster_dpi.round(6)
+    if not page_dpi:
+        page_dpi = raster_dpi
+
+    args_gs = (
+        [
+            GS,
+            '-dQUIET',
+            '-dSAFER',
+            '-dBATCH',
+            '-dNOPAUSE',
+            f'-sDEVICE={raster_device}',
+            f'-dFirstPage={pageno}',
+            f'-dLastPage={pageno}',
+            f'-r{raster_dpi.x:f}x{raster_dpi.y:f}',
+        ]
+        + (['-dFILTERVECTOR'] if filter_vector else [])
+        + [
+            '-o',
+            '-',
+            '-sstdout=%stderr',
+            '-dAutoRotatePages=/None',  # Probably has no effect on raster
+            '-f',
+            fspath(input_file),
+        ]
+    )
+
+    try:
+        p = run(args_gs, stdout=PIPE, stderr=PIPE, check=True)
+    except CalledProcessError as e:
+        log.error(e.stderr.decode(errors='replace'))
+        raise SubprocessOutputError('Ghostscript rasterizing failed')
+    else:
+        stderr = p.stderr.decode(errors='replace')
+        if _gs_error_reported(stderr):
+            log.error(stderr)
+        elif stderr:
+            log.debug(stderr)
+
+    with Image.open(BytesIO(p.stdout)) as im:
+        if rotation is not None:
+            log.debug("Rotating output by %i", rotation)
+            # rotation is a clockwise angle and Image.ROTATE_* is
+            # counterclockwise so this cancels out the rotation
+            if rotation == 90:
+                im = im.transpose(Image.ROTATE_90)
+            elif rotation == 180:
+                im = im.transpose(Image.ROTATE_180)
+            elif rotation == 270:
+                im = im.transpose(Image.ROTATE_270)
+            if rotation % 180 == 90:
+                page_dpi = page_dpi.flip_axis()
+        im.save(fspath(output_file), dpi=page_dpi)
+
+
+def generate_pdfa(
+    pdf_pages,
+    output_file: os.PathLike,
+    compression: str,
+    pdf_version: str = '1.5',
+    pdfa_part: str = '2',
+):
+    compression_args = []
+    if compression == 'jpeg':
+        compression_args = [
+            "-dAutoFilterColorImages=false",
+            "-dColorImageFilter=/DCTEncode",
+            "-dAutoFilterGrayImages=false",
+            "-dGrayImageFilter=/DCTEncode",
+        ]
+    elif compression == 'lossless':
+        compression_args = [
+            "-dAutoFilterColorImages=false",
+            "-dColorImageFilter=/FlateEncode",
+            "-dAutoFilterGrayImages=false",
+            "-dGrayImageFilter=/FlateEncode",
+        ]
+    else:
+        compression_args = [
+            "-dAutoFilterColorImages=true",
+            "-dAutoFilterGrayImages=true",
+        ]
+
+    # Older versions of Ghostscript expect a leading slash in
+    # sColorConversionStrategy, newer ones should not have it. See Ghostscript
+    # git commit fe1c025d.
+    strategy = 'RGB' if version() >= '9.19' else '/RGB'
+
+    if version() == '9.23':
+        # 9.23: new feature JPEG passthrough is broken in some cases, best to
+        # disable it always
+        # https://bugs.ghostscript.com/show_bug.cgi?id=699216
+        compression_args.append('-dPassThroughJPEGImages=false')
+
+    # nb no need to specify ProcessColorModel when ColorConversionStrategy
+    # is set; see:
+    # https://bugs.ghostscript.com/show_bug.cgi?id=699392
+    args_gs = (
+        [
+            GS,
+            "-dQUIET",
+            "-dBATCH",
+            "-dNOPAUSE",
+            "-dSAFER",
+            "-dCompatibilityLevel=" + str(pdf_version),
+            "-sDEVICE=pdfwrite",
+            "-dAutoRotatePages=/None",
+            "-sColorConversionStrategy=" + strategy,
+        ]
+        + compression_args
+        + [
+            "-dJPEGQ=95",
+            "-dPDFA=" + pdfa_part,
+            "-dPDFACompatibilityPolicy=1",
+            "-o",
+            "-",
+            "-sstdout=%stderr",
+        ]
+    )
+    args_gs.extend(fspath(s) for s in pdf_pages)  # Stringify Path objs
+    try:
+        with Path(output_file).open('wb') as output:
+            p = run(args_gs, stdout=output, stderr=PIPE, check=True)
+    except CalledProcessError as e:
+        # Ghostscript does not change return code when it fails to create
+        # PDF/A - check PDF/A status elsewhere
+        log.error(e.stderr.decode(errors='replace'))
+        raise SubprocessOutputError('Ghostscript PDF/A rendering failed')
+    else:
+        stderr = p.stderr.decode('utf-8', errors='replace')
+        if _gs_error_reported(stderr):
+            last_part = None
+            repcount = 0
+            for part in stderr.split('****'):
+                if part != last_part:
+                    if repcount > 1:
+                        log.error(f"(previous error message repeated {repcount} times)")
+                        repcount = 0
+                    log.error(part)
+                else:
+                    repcount += 1
+                last_part = part
+        elif 'overprint mode not set' in stderr:
+            # Unless someone is going to print PDF/A documents on a
+            # magical sRGB printer I can't see the removal of overprinting
+            # being a problem....
+            log.debug(
+                "Ghostscript had to remove PDF 'overprinting' from the "
+                "input file to complete PDF/A conversion. "
+            )

src/ocrmypdf/_exec/jbig2enc.py

@@ -15,14 +15,14 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
-from functools import lru_cache
-from subprocess import PIPE, run
+"""Interface to jbig2 executable"""
 
-from . import get_version
-from ..exceptions import MissingDependencyError
+from subprocess import PIPE
+
+from ocrmypdf.exceptions import MissingDependencyError
+from ocrmypdf.subprocess import get_version, run
 
 
-@lru_cache(maxsize=1)
 def version():
     return get_version('jbig2', regex=r'jbig2enc (\d+(\.\d+)*).*')
 

src/ocrmypdf/_exec/pngquant.py

@@ -15,17 +15,17 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
-from functools import lru_cache
-from subprocess import run
+"""Interface to pngquant executable"""
+
+from os import fspath
 from tempfile import NamedTemporaryFile
 
 from PIL import Image
 
-from . import get_version
-from ..exceptions import MissingDependencyError
+from ocrmypdf.exceptions import MissingDependencyError
+from ocrmypdf.subprocess import get_version, run
 
 
-@lru_cache(maxsize=1)
 def version():
     return get_version('pngquant', regex=r'(\d+(\.\d+)*).*')
 
@@ -39,9 +39,10 @@ def available():
 
 
 def quantize(input_file, output_file, quality_min, quality_max):
+    input_file = fspath(input_file)
+    output_file = fspath(output_file)
     if input_file.endswith('.jpg'):
-        im = Image.open(input_file)
-        with NamedTemporaryFile(suffix='.png') as tmp:
+        with Image.open(input_file) as im, NamedTemporaryFile(suffix='.png') as tmp:
             im.save(tmp)
             args = [
                 'pngquant',

src/ocrmypdf/_exec/tesseract.py

@@ -15,26 +15,27 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
+"""Interface to Tesseract executable"""
+
+import logging
 import os
 import shutil
-import sys
 from collections import namedtuple
-from contextlib import suppress
-from functools import lru_cache
 from os import fspath
-from subprocess import (
-    PIPE,
-    STDOUT,
-    CalledProcessError,
-    TimeoutExpired,
-    check_output,
-    run,
-)
-from textwrap import dedent
+from pathlib import Path
+from subprocess import PIPE, STDOUT, CalledProcessError, TimeoutExpired
+from typing import List
 
-from . import get_version
-from ..exceptions import MissingDependencyError, TesseractConfigError
-from ..helpers import page_number
+from PIL import Image
+
+from ocrmypdf.exceptions import (
+    MissingDependencyError,
+    SubprocessOutputError,
+    TesseractConfigError,
+)
+from ocrmypdf.subprocess import get_version, run
+
+log = logging.getLogger(__name__)
 
 OrientationConfidence = namedtuple('OrientationConfidence', ('angle', 'confidence'))
 
@@ -56,46 +57,55 @@ HOCR_TEMPLATE = """<?xml version="1.0" encoding="UTF-8"?>
 """
 
 
-@lru_cache(maxsize=1)
+class TesseractLoggerAdapter(logging.LoggerAdapter):
+    def process(self, msg, kwargs):
+        kwargs['extra'] = self.extra
+        return '[tesseract] %s' % (msg), kwargs
+
+
 def version():
     return get_version('tesseract', regex=r'tesseract\s(.+)')
 
 
-def v4():
-    "Is this Tesseract v4.0?"
-    return version() >= '4'
-
-
-@lru_cache(maxsize=1)
-def has_textonly_pdf():
+def has_textonly_pdf(langs=None):
     """Does Tesseract have textonly_pdf capability?
 
     Available in v4.00.00alpha since January 2017. Best to
-    parse the parameter list
+    parse the parameter list.
     """
-    args_tess = ['tesseract', '--print-parameters', 'pdf']
+    args_tess = tess_base_args(langs, engine_mode=None) + ['--print-parameters', 'pdf']
     params = ''
     try:
-        params = check_output(args_tess, universal_newlines=True, stderr=STDOUT)
+        proc = run(args_tess, check=True, stdout=PIPE, stderr=STDOUT)
+        params = proc.stdout
     except CalledProcessError as e:
-        print("Could not --print-parameters from tesseract", file=sys.stderr)
-        raise MissingDependencyError from e
-    if 'textonly_pdf' in params:
+        raise MissingDependencyError(
+            "Could not --print-parameters from tesseract. This can happen if the "
+            "TESSDATA_PREFIX environment is not set to a valid tessdata folder. "
+        ) from e
+    if b'textonly_pdf' in params:
         return True
     return False
 
 
-@lru_cache(maxsize=1)
-def languages():
+def has_user_words():
+    """Does Tesseract have --user-words capability?
+
+    Not available in 4.0, but available in 4.1. Also available in 3.x, but
+    we no longer support 3.x.
+    """
+    return version() >= '4.1'
+
+
+def get_languages():
     def lang_error(output):
-        msg = dedent(
-            """Tesseract failed to report available languages.
-        Output from Tesseract:
-        -----------
-        """
+        msg = (
+            "Tesseract failed to report available languages.\n"
+            "Output from Tesseract:\n"
+            "-----------\n"
         )
         msg += output
-        print(msg, file=sys.stderr)
+        return msg
 
     args_tess = ['tesseract', '--list-langs']
     try:
@@ -104,26 +114,25 @@ def languages():
         )
         output = proc.stdout
     except CalledProcessError as e:
-        lang_error(e.output)
-        raise MissingDependencyError from e
+        raise MissingDependencyError(lang_error(e.output)) from e
 
-    header, *rest = output.splitlines()
-    if not header.startswith('List of available languages'):
-        lang_error(output)
-        raise MissingDependencyError
+    for line in output.splitlines():
+        if line.startswith('Error'):
+            raise MissingDependencyError(lang_error(output))
+    _header, *rest = output.splitlines()
     return set(lang.strip() for lang in rest)
 
 
-def tess_base_args(langs, engine_mode):
+def tess_base_args(langs: List[str], engine_mode: int) -> List[str]:
     args = ['tesseract']
     if langs:
         args.extend(['-l', '+'.join(langs)])
-    if engine_mode is not None and v4():
+    if engine_mode is not None:
         args.extend(['--oem', str(engine_mode)])
     return args
 
 
-def get_orientation(input_file, engine_mode, timeout: float, log):
+def get_orientation(input_file: Path, engine_mode: int, timeout: float):
     args_tesseract = tess_base_args(['osd'], engine_mode) + [
         '--psm',
         '0',
@@ -132,17 +141,19 @@ def get_orientation(input_file, engine_mode, timeout: float, log):
     ]
 
     try:
-        stdout = check_output(args_tesseract, stderr=STDOUT, timeout=timeout)
+        p = run(args_tesseract, stdout=PIPE, stderr=STDOUT, timeout=timeout, check=True)
+        stdout = p.stdout
     except TimeoutExpired:
         return OrientationConfidence(angle=0, confidence=0.0)
     except CalledProcessError as e:
-        tesseract_log_output(log, e.output, input_file)
+        tesseract_log_output(e.stdout)
+        tesseract_log_output(e.stderr)
         if (
             b'Too few characters. Skipping this page' in e.output
             or b'Image too large' in e.output
         ):
             return OrientationConfidence(0, 0)
-        raise e from e
+        raise SubprocessOutputError() from e
     else:
         osd = {}
         for line in stdout.decode().splitlines():
@@ -158,19 +169,17 @@ def get_orientation(input_file, engine_mode, timeout: float, log):
         return oc
 
 
-def tesseract_log_output(log, stdout, input_file):
-    prefix = f"{(page_number(input_file)):4d}: [tesseract] "
+def tesseract_log_output(stream):
+    tlog = TesseractLoggerAdapter(
+        log, extra=log.extra if hasattr(log, 'extra') else None
+    )
 
+    if not stream:
+        return
     try:
-        text = stdout.decode()
+        text = stream.decode()
     except UnicodeDecodeError:
-        log.error(
-            prefix
-            + "command line output was not utf-8. "
-            + "This usually means Tesseract's language packs do not match "
-            "the installed version of Tesseract."
-        )
-        text = stdout.decode('utf-8', 'backslashreplace')
+        text = stream.decode('utf-8', 'ignore')
 
     lines = text.splitlines()
     for line in lines:
@@ -179,66 +188,58 @@ def tesseract_log_output(log, stdout, input_file):
         elif line.startswith("Warning in pixReadMem"):
             continue
         elif 'diacritics' in line:
-            log.warning(prefix + "lots of diacritics - possibly poor OCR")
+            tlog.warning("lots of diacritics - possibly poor OCR")
         elif line.startswith('OSD: Weak margin'):
-            log.warning(prefix + "unsure about page orientation")
+            tlog.warning("unsure about page orientation")
         elif 'Error in pixScanForForeground' in line:
             pass  # Appears to be spurious/problem with nonwhite borders
         elif 'Error in boxClipToRectangle' in line:
             pass  # Always appears with pixScanForForeground message
         elif 'parameter not found: ' in line.lower():
-            log.error(prefix + line.strip())
+            tlog.error(line.strip())
             problem = line.split('found: ')[1]
             raise TesseractConfigError(problem)
         elif 'error' in line.lower() or 'exception' in line.lower():
-            log.error(prefix + line.strip())
+            tlog.error(line.strip())
         elif 'warning' in line.lower():
-            log.warning(prefix + line.strip())
+            tlog.warning(line.strip())
         elif 'read_params_file' in line.lower():
-            log.error(prefix + line.strip())
+            tlog.error(line.strip())
         else:
-            log.info(prefix + line.strip())
+            tlog.info(line.strip())
 
 
-def page_timedout(log, input_file, timeout):
+def page_timedout(timeout):
     if timeout == 0:
         return
-    prefix = f"{(page_number(input_file)):4d}: [tesseract] "
-    log.warning(prefix + " took too long to OCR - skipping")
+    log.warning("[tesseract] took too long to OCR - skipping")
 
 
-def _generate_null_hocr(output_hocr, output_sidecar, image):
+def _generate_null_hocr(output_hocr, output_text, image):
     """Produce a .hocr file that reports no text detected on a page that is
     the same size as the input image."""
-    from PIL import Image
+    with Image.open(image) as im:
+        w, h = im.size
 
-    im = Image.open(image)
-    w, h = im.size
-
-    with open(output_hocr, 'w', encoding="utf-8") as f:
-        f.write(HOCR_TEMPLATE.format(w, h))
-    with open(output_sidecar, 'w', encoding='utf-8') as f:
-        f.write('[skipped page]')
+    output_hocr.write_text(HOCR_TEMPLATE.format(w, h), encoding='utf-8')
+    output_text.write_text('[skipped page]', encoding='utf-8')
 
 
 def generate_hocr(
-    input_file,
-    output_files,
-    language: list,
-    engine_mode,
-    tessconfig: list,
+    input_file: Path,
+    output_hocr: Path,
+    output_text: Path,
+    languages: List[str],
+    engine_mode: int,
+    tessconfig: List[str],
     timeout: float,
     pagesegmode: int,
     user_words,
     user_patterns,
-    log,
 ):
+    prefix = output_hocr.with_suffix('')
 
-    output_hocr = next(o for o in output_files if o.endswith('.hocr'))
-    output_sidecar = next(o for o in output_files if o.endswith('.txt'))
-    prefix = os.path.splitext(output_hocr)[0]
-
-    args_tesseract = tess_base_args(language, engine_mode)
+    args_tesseract = tess_base_args(languages, engine_mode)
 
     if pagesegmode is not None:
         args_tesseract.extend(['--psm', str(pagesegmode)])
@@ -249,86 +250,70 @@ def generate_hocr(
     if user_patterns:
         args_tesseract.extend(['--user-patterns', user_patterns])
 
-    # Reminder: test suite tesseract spoofers will break after any changes
+    # Reminder: test suite tesseract test plugins will break after any changes
     # to the number of order parameters here
     args_tesseract.extend([input_file, prefix, 'hocr', 'txt'] + tessconfig)
     try:
-        log.debug(args_tesseract)
-        stdout = check_output(args_tesseract, stderr=STDOUT, timeout=timeout)
+        p = run(args_tesseract, stdout=PIPE, stderr=STDOUT, timeout=timeout, check=True)
+        stdout = p.stdout
     except TimeoutExpired:
         # Generate a HOCR file with no recognized text if tesseract times out
         # Temporary workaround to hocrTransform not being able to function if
         # it does not have a valid hOCR file.
-        page_timedout(log, input_file, timeout)
-        _generate_null_hocr(output_hocr, output_sidecar, input_file)
+        page_timedout(timeout)
+        _generate_null_hocr(output_hocr, output_text, input_file)
     except CalledProcessError as e:
-        tesseract_log_output(log, e.output, input_file)
+        tesseract_log_output(e.output)
         if b'Image too large' in e.output:
-            _generate_null_hocr(output_hocr, output_sidecar, input_file)
+            _generate_null_hocr(output_hocr, output_text, input_file)
             return
 
-        raise e from e
+        raise SubprocessOutputError() from e
     else:
-        tesseract_log_output(log, stdout, input_file)
+        tesseract_log_output(stdout)
         # The sidecar text file will get the suffix .txt; rename it to
         # whatever caller wants it named
-        if os.path.exists(prefix + '.txt'):
-            shutil.move(prefix + '.txt', output_sidecar)
+        if prefix.with_suffix('.txt').exists():
+            shutil.move(prefix.with_suffix('.txt'), output_text)
 
 
-def use_skip_page(text_only, skip_pdf, output_pdf, output_text):
-    with open(output_text, 'w') as f:
-        f.write('[skipped page]')
+def use_skip_page(output_pdf, output_text):
+    output_text.write_text('[skipped page]', encoding='utf-8')
 
-    if skip_pdf and not text_only:
-        # Substitute a "skipped page"
-        with suppress(FileNotFoundError):
-            os.remove(output_pdf)  # In case it was partially created
-        os.symlink(skip_pdf, output_pdf)
-        return
-
-    # Or normally, just write a 0 byte file to the output to indicate a skip
-    with open(output_pdf, 'wb') as out:
-        out.write(b'')
+    # A 0 byte file to the output to indicate a skip
+    output_pdf.write_bytes(b'')
 
 
 def generate_pdf(
     *,
-    input_image,
-    skip_pdf=None,
-    output_pdf,
-    output_text,
-    language: list,
-    engine_mode,
-    text_only: bool,
-    tessconfig: list,
+    input_file: Path,
+    output_pdf: Path,
+    output_text: Path,
+    languages: List[str],
+    engine_mode: int,
+    tessconfig: List[str],
     timeout: float,
     pagesegmode: int,
     user_words,
     user_patterns,
-    log,
 ):
-    '''Use Tesseract to render a PDF.
+    """Use Tesseract to render a PDF.
 
-    input_image -- image to analyze
-    skip_pdf -- if we time out, use this file as output
+    input_file -- image to analyze
     output_pdf -- file to generate
     output_text -- OCR text file
-    language -- list of languages to consider
+    languages -- list of languages to consider
     engine_mode -- engine mode argument for tess v4
-    text_only -- enable tesseract text only mode?
     tessconfig -- tesseract configuration
     timeout -- timeout (seconds)
-    log -- logger object
-    '''
+    """
 
-    args_tesseract = tess_base_args(language, engine_mode)
+    args_tesseract = tess_base_args(languages, engine_mode)
 
     if pagesegmode is not None:
         args_tesseract.extend(['--psm', str(pagesegmode)])
 
-    if text_only and has_textonly_pdf():
-        args_tesseract.extend(['-c', 'textonly_pdf=1'])
+    args_tesseract.extend(['-c', 'textonly_pdf=1'])
 
     if user_words:
         args_tesseract.extend(['--user-words', user_words])
@@ -338,24 +323,23 @@ def generate_pdf(
 
     prefix = os.path.splitext(output_pdf)[0]  # Tesseract appends suffixes
 
-    # Reminder: test suite tesseract spoofers might break after any changes
+    # Reminder: test suite tesseract test plugins might break after any changes
     # to the number of order parameters here
 
-    args_tesseract.extend([input_image, prefix, 'pdf', 'txt'] + tessconfig)
-
+    args_tesseract.extend([input_file, prefix, 'pdf', 'txt'] + tessconfig)
     try:
-        log.debug(args_tesseract)
-        stdout = check_output(args_tesseract, stderr=STDOUT, timeout=timeout)
+        p = run(args_tesseract, stdout=PIPE, stderr=STDOUT, timeout=timeout, check=True)
+        stdout = p.stdout
         if os.path.exists(prefix + '.txt'):
             shutil.move(prefix + '.txt', output_text)
     except TimeoutExpired:
-        page_timedout(log, input_image, timeout)
-        use_skip_page(text_only, skip_pdf, output_pdf, output_text)
+        page_timedout(timeout)
+        use_skip_page(output_pdf, output_text)
     except CalledProcessError as e:
-        tesseract_log_output(log, e.output, input_image)
+        tesseract_log_output(e.output)
         if b'Image too large' in e.output:
-            use_skip_page(text_only, skip_pdf, output_pdf, output_text)
+            use_skip_page(output_pdf, output_text)
             return
-        raise e from e
+        raise SubprocessOutputError() from e
     else:
-        tesseract_log_output(log, stdout, input_image)
+        tesseract_log_output(stdout)

src/ocrmypdf/_exec/unpaper.py

@@ -18,59 +18,68 @@
 # unpaper documentation:
 # https://github.com/Flameeyes/unpaper/blob/master/doc/basic-concepts.md
 
+"""Interface to unpaper executable"""
+
+import logging
 import os
 import shlex
-import subprocess
-import sys
-from functools import lru_cache
+from pathlib import Path
 from subprocess import PIPE, STDOUT, CalledProcessError
 from tempfile import TemporaryDirectory
+from typing import Tuple
 
-from . import get_version
-from ..exceptions import MissingDependencyError, SubprocessOutputError
+from PIL import Image
 
-try:
-    from PIL import Image
-except ImportError:
-    print("Could not find Python3 imaging library", file=sys.stderr)
-    raise
+from ocrmypdf.exceptions import MissingDependencyError, SubprocessOutputError
+from ocrmypdf.subprocess import get_version
+from ocrmypdf.subprocess import run as external_run
+
+log = logging.getLogger(__name__)
 
 
-@lru_cache(maxsize=1)
 def version():
     return get_version('unpaper')
 
 
-def run(input_file, output_file, dpi, log, mode_args):
+def _setup_unpaper_io(tmpdir: Path, input_file: Path) -> Tuple[Path, Path]:
+    SUFFIXES = {'1': '.pbm', 'L': '.pgm', 'RGB': '.ppm'}
+    with Image.open(input_file) as im:
+        im_modified = False
+        if im.mode not in SUFFIXES:
+            log.info("Converting image to other colorspace")
+            try:
+                if im.mode == 'P' and len(im.getcolors()) == 2:
+                    im = im.convert(mode='1')
+                else:
+                    im = im.convert(mode='RGB')
+            except IOError as e:
+                raise MissingDependencyError(
+                    "Could not convert image with type " + im.mode
+                ) from e
+            else:
+                im_modified = True
+        try:
+            suffix = SUFFIXES[im.mode]
+        except KeyError:
+            raise MissingDependencyError(
+                "Failed to convert image to a supported format."
+            ) from e
+
+        if im_modified or input_file.suffix != '.png':
+            input_png = tmpdir / 'input.png'
+            im.save(input_png, format='PNG', compress_level=1)
+        else:
+            # No changes, PNG input, just use the file we already have
+            input_png = input_file
+        output_pnm = tmpdir / f'output{suffix}'
+    return input_png, output_pnm
+
+
+def run(input_file, output_file, dpi, mode_args):
     args_unpaper = ['unpaper', '-v', '--dpi', str(dpi)] + mode_args
 
-    SUFFIXES = {'1': '.pbm', 'L': '.pgm', 'RGB': '.ppm'}
-
-    im = Image.open(input_file)
-    if im.mode not in SUFFIXES.keys():
-        log.info("Converting image to other colorspace")
-        try:
-            if im.mode == 'P' and len(im.getcolors()) == 2:
-                im = im.convert(mode='1')
-            else:
-                im = im.convert(mode='RGB')
-        except IOError as e:
-            log.error("Could not convert image with type " + im.mode)
-            im.close()
-            raise MissingDependencyError() from e
-
-    try:
-        suffix = SUFFIXES[im.mode]
-    except KeyError:
-        log.error("Failed to convert image to a supported format.")
-        im.close()
-        raise MissingDependencyError() from e
-
     with TemporaryDirectory() as tmpdir:
-        input_pnm = os.path.join(tmpdir, f'input{suffix}')
-        output_pnm = os.path.join(tmpdir, f'output{suffix}')
-        im.save(input_pnm, format='PPM')
-        im.close()
+        input_png, output_pnm = _setup_unpaper_io(Path(tmpdir), input_file)
 
         # To prevent any shenanigans from accepting arbitrary parameters in
         # --unpaper-args, we:
@@ -79,28 +88,29 @@ def run(input_file, output_file, dpi, log, mode_args):
         # 3) append absolute paths for the input and output file
         # This should ensure that a user cannot clobber some other file with
         # their unpaper arguments (whether intentionally or otherwise)
-        args_unpaper.extend([input_pnm, output_pnm])
+        args_unpaper.extend([os.fspath(input_png), os.fspath(output_pnm)])
         try:
-            proc = subprocess.run(
+            proc = external_run(
                 args_unpaper,
                 check=True,
                 close_fds=True,
                 universal_newlines=True,
-                stderr=STDOUT,
-                cwd=tmpdir,
+                stderr=STDOUT,  # unpaper writes logging output to stdout and stderr
+                cwd=tmpdir,  # and cannot send file output to stdout
                 stdout=PIPE,
             )
         except CalledProcessError as e:
-            log.debug(e.output)
+            log.debug(e.stderr)
             raise e from e
         else:
-            log.debug(proc.stdout)
-            # unpaper sets dpi to 72; fix this
+            log.debug(proc.stderr)
             try:
-                Image.open(output_pnm).save(output_file, dpi=(dpi, dpi))
+                with Image.open(output_pnm) as imout:
+                    imout.save(output_file, dpi=(dpi, dpi))
             except (FileNotFoundError, OSError):
                 raise SubprocessOutputError(
-                    "unpaper: failed to produce the expected output file. Called with: "
+                    "unpaper: failed to produce the expected output file. "
+                    + " Called with: "
                     + str(args_unpaper)
                 ) from None
 
@@ -112,7 +122,7 @@ def validate_custom_args(args: str):
     return unpaper_args
 
 
-def clean(input_file, output_file, dpi, log, unpaper_args=None):
+def clean(input_file, output_file, dpi, unpaper_args=None):
     default_args = [
         '--layout',
         'none',
@@ -126,4 +136,4 @@ def clean(input_file, output_file, dpi, log, unpaper_args=None):
     ]
     if not unpaper_args:
         unpaper_args = default_args
-    run(input_file, output_file, dpi, log, unpaper_args)
+    run(input_file, output_file, dpi, unpaper_args)

src/ocrmypdf/_graft.py

@@ -0,0 +1,301 @@
+# © 2018 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+from contextlib import suppress
+from pathlib import Path
+from typing import Optional
+
+import pikepdf
+
+log = logging.getLogger(__name__)
+MAX_REPLACE_PAGES = 100
+
+
+def _update_page_resources(*, page, font, font_key, procset):
+    """Update this page's fonts with a reference to the Glyphless font"""
+
+    if '/Resources' not in page:
+        page['/Resources'] = pikepdf.Dictionary({})
+    resources = page['/Resources']
+    try:
+        fonts = resources['/Font']
+    except KeyError:
+        fonts = pikepdf.Dictionary({})
+    if font_key is not None and font_key not in fonts:
+        fonts[font_key] = font
+    resources['/Font'] = fonts
+
+    # Reassign /ProcSet to one that just lists everything - ProcSet is
+    # obsolete and doesn't matter but recommended for old viewer support
+    resources['/ProcSet'] = procset
+
+
+def strip_invisible_text(pdf, page):
+    stream = []
+    in_text_obj = False
+    render_mode = 0
+    text_objects = []
+
+    page.page_contents_coalesce()
+    for operands, operator in pikepdf.parse_content_stream(page, ''):
+        if not in_text_obj:
+            if operator == pikepdf.Operator('BT'):
+                in_text_obj = True
+                render_mode = 0
+                text_objects.append((operands, operator))
+            else:
+                stream.append((operands, operator))
+        else:
+            if operator == pikepdf.Operator('Tr'):
+                render_mode = operands[0]
+            text_objects.append((operands, operator))
+            if operator == pikepdf.Operator('ET'):
+                in_text_obj = False
+                if render_mode != 3:
+                    stream.extend(text_objects)
+                text_objects.clear()
+
+    def convert(op):
+        try:
+            return op.unparse()
+        except AttributeError:
+            return str(op).encode('ascii')
+
+    lines = []
+
+    for operands, operator in stream:
+        if operator == pikepdf.Operator('INLINE IMAGE'):
+            iim = operands[0]
+            line = iim.unparse()
+        else:
+            line = b' '.join(convert(op) for op in operands) + b' ' + operator.unparse()
+        lines.append(line)
+
+    content_stream = b'\n'.join(lines)
+    page.Contents = pikepdf.Stream(pdf, content_stream)
+
+
+class OcrGrafter:
+    def __init__(self, context):
+        self.context = context
+        self.path_base = context.origin
+
+        self.pdf_base = pikepdf.open(self.path_base)
+        self.font, self.font_key = None, None
+
+        self.pdfinfo = context.pdfinfo
+        self.output_file = context.get_path('graft_layers.pdf')
+
+        self.procset = self.pdf_base.make_indirect(
+            pikepdf.Object.parse(b'[ /PDF /Text /ImageB /ImageC /ImageI ]')
+        )
+
+        self.emplacements = 1
+        self.interim_count = 0
+
+    def graft_page(
+        self,
+        *,
+        pageno: int,
+        image: Optional[Path],
+        textpdf: Optional[Path],
+        autorotate_correction: int,
+    ):
+        if textpdf and not self.font:
+            self.font, self.font_key = self._find_font(textpdf)
+
+        emplaced_page = False
+        content_rotation = self.pdfinfo[pageno].rotation
+        path_image = Path(image).resolve() if image else None
+        if path_image is not None and path_image != self.path_base:
+            # We are updating the old page with a rasterized PDF of the new
+            # page (without changing objgen, to preserve references)
+            log.debug("Emplacement update")
+            with pikepdf.open(image) as pdf_image:
+                self.emplacements += 1
+                foreign_image_page = pdf_image.pages[0]
+                self.pdf_base.pages.append(foreign_image_page)
+                local_image_page = self.pdf_base.pages[-1]
+                self.pdf_base.pages[pageno].emplace(local_image_page)
+                del self.pdf_base.pages[-1]
+            emplaced_page = True
+
+        if emplaced_page:
+            content_rotation = autorotate_correction
+        text_rotation = autorotate_correction
+        text_misaligned = (text_rotation - content_rotation) % 360
+        log.debug(
+            f"Rotations for page {pageno}: [text, auto, misalign, content] = "
+            f"{text_rotation}, {autorotate_correction}, "
+            f"{text_misaligned}, {content_rotation}"
+        )
+
+        if textpdf and self.font:
+            # Graft the text layer onto this page, whether new or old
+            strip_old = self.context.options.redo_ocr
+            self._graft_text_layer(
+                page_num=pageno + 1,
+                textpdf=textpdf,
+                font=self.font,
+                font_key=self.font_key,
+                rotation=text_misaligned,
+                procset=self.procset,
+                strip_old_text=strip_old,
+            )
+
+        # Correct the rotation if applicable
+        self.pdf_base.pages[pageno].Rotate = (
+            content_rotation - autorotate_correction
+        ) % 360
+
+        if self.emplacements % MAX_REPLACE_PAGES == 0:
+            self.save_and_reload()
+
+    def save_and_reload(self):
+        """Save and reload the Pdf.
+
+        This will keep a lid on our memory usage for very large files. Attach
+        the font to page 1 even if page 1 doesn't use it, so we have a way to get it
+        back.
+        """
+
+        page0 = self.pdf_base.pages[0]
+        _update_page_resources(
+            page=page0, font=self.font, font_key=self.font_key, procset=self.procset
+        )
+
+        # We cannot read and write the same file, that will corrupt it
+        # but we don't to keep more copies than we need to. Delete intermediates.
+        # {interim_count} is the opened file we were updateing
+        # {interim_count - 1} can be deleted
+        # {interim_count + 1} is the new file will produce and open
+        old_file = self.output_file.with_suffix(f'.working{self.interim_count - 1}.pdf')
+        if not self.context.options.keep_temporary_files:
+            with suppress(FileNotFoundError):
+                old_file.unlink()
+
+        next_file = self.output_file.with_suffix(
+            f'.working{self.interim_count + 1}.pdf'
+        )
+        self.pdf_base.save(next_file)
+        self.pdf_base.close()
+
+        self.pdf_base = pikepdf.open(next_file)
+        self.procset = self.pdf_base.pages[0].Resources.ProcSet
+        self.font, self.font_key = None, None  # Ensure we reacquire this information
+        self.interim_count += 1
+
+    def finalize(self):
+        self.pdf_base.save(self.output_file)
+        self.pdf_base.close()
+        return self.output_file
+
+    def _find_font(self, text):
+        """Copy a font from the filename text into pdf_base"""
+
+        font, font_key = None, None
+        possible_font_names = ('/f-0-0', '/F1')
+        try:
+            with pikepdf.open(text) as pdf_text:
+                try:
+                    pdf_text_fonts = pdf_text.pages[0].Resources.get('/Font', {})
+                except (AttributeError, IndexError, KeyError):
+                    return None, None
+                for f in possible_font_names:
+                    pdf_text_font = pdf_text_fonts.get(f, None)
+                    if pdf_text_font is not None:
+                        font_key = f
+                        break
+                if pdf_text_font:
+                    font = self.pdf_base.copy_foreign(pdf_text_font)
+                return font, font_key
+        except (FileNotFoundError, pikepdf.PdfError):
+            # PdfError occurs if a 0-length file is written e.g. due to OCR timeout
+            return None, None
+
+    def _graft_text_layer(
+        self,
+        *,
+        page_num: int,
+        textpdf: Path,
+        font: pikepdf.Object,
+        font_key: pikepdf.Object,
+        procset: pikepdf.Object,
+        rotation: int,
+        strip_old_text: bool,
+    ):
+        """Insert the text layer from text page 0 on to pdf_base at page_num"""
+
+        log.debug("Grafting")
+        if Path(textpdf).stat().st_size == 0:
+            return
+
+        # This is a pointer indicating a specific page in the base file
+        with pikepdf.open(textpdf) as pdf_text:
+            pdf_text_contents = pdf_text.pages[0].Contents.read_bytes()
+
+            base_page = self.pdf_base.pages.p(page_num)
+
+            # The text page always will be oriented up by this stage but the original
+            # content may have a rotation applied. Wrap the text stream with a rotation
+            # so it will be oriented the same way as the rest of the page content.
+            # (Previous versions OCRmyPDF rotated the content layer to match the text.)
+            mediabox = [float(pdf_text.pages[0].MediaBox[v]) for v in range(4)]
+            wt, ht = mediabox[2] - mediabox[0], mediabox[3] - mediabox[1]
+
+            mediabox = [float(base_page.MediaBox[v]) for v in range(4)]
+            wp, hp = mediabox[2] - mediabox[0], mediabox[3] - mediabox[1]
+
+            translate = pikepdf.PdfMatrix().translated(-wt / 2, -ht / 2)
+            untranslate = pikepdf.PdfMatrix().translated(wp / 2, hp / 2)
+            corner = pikepdf.PdfMatrix().translated(mediabox[0], mediabox[1])
+            # -rotation because the input is a clockwise angle and this formula
+            # uses CCW
+            rotation = -rotation % 360
+            rotate = pikepdf.PdfMatrix().rotated(rotation)
+
+            # Because of rounding of DPI, we might get a text layer that is not
+            # identically sized to the target page. Scale to adjust. Normally this
+            # is within 0.998.
+            if rotation in (90, 270):
+                wt, ht = ht, wt
+            scale_x = wp / wt
+            scale_y = hp / ht
+
+            # log.debug('%r', scale_x, scale_y)
+            scale = pikepdf.PdfMatrix().scaled(scale_x, scale_y)
+
+            # Translate the text so it is centered at (0, 0), rotate it there, adjust
+            # for a size different between initial and text PDF, then untranslate, and
+            # finally move the lower left corner to match the mediabox
+            ctm = translate @ rotate @ scale @ untranslate @ corner
+
+            pdf_text_contents = (
+                b'q %s cm\n' % ctm.encode() + pdf_text_contents + b'\nQ\n'
+            )
+
+            new_text_layer = pikepdf.Stream(self.pdf_base, pdf_text_contents)
+
+            if strip_old_text:
+                strip_invisible_text(self.pdf_base, base_page)
+
+            base_page.page_contents_add(new_text_layer, prepend=True)
+
+            _update_page_resources(
+                page=base_page, font=font, font_key=font_key, procset=procset
+            )

src/ocrmypdf/_jobcontext.py

@@ -15,69 +15,75 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
+import os
 import shutil
 import sys
-from contextlib import suppress
-from multiprocessing.managers import SyncManager
+from argparse import Namespace
+from copy import copy
+from io import IOBase
+from pathlib import Path
+from typing import Iterator
 
-from .pdfinfo import PdfInfo
+from ocrmypdf.pdfinfo import PdfInfo
 
 
-class JobContext:
-    """Holds our context for a particular run of the pipeline
+class PdfContext:
+    """Holds our context for a particular run of the pipeline"""
 
-    A multiprocessing manager effectively creates a separate process
-    that keeps the master job context object.  Other threads access
-    job context via multiprocessing proxy objects.
+    def __init__(
+        self,
+        options: Namespace,
+        work_folder: Path,
+        origin: Path,
+        pdfinfo: PdfInfo,
+        plugin_manager,
+    ):
+        self.options = options
+        self.work_folder = work_folder
+        self.origin = origin
+        self.pdfinfo = pdfinfo
+        self.plugin_manager = plugin_manager
 
-    While this would naturally lend itself @property's it seems to make
-    a little more sense to use functions to make it explicitly that the
-    invocation requires marshalling data across a process boundary.
+    def get_path(self, name: str) -> Path:
+        return self.work_folder / name
 
+    def get_page_contexts(self) -> Iterator['PageContext']:
+        npages = len(self.pdfinfo)
+        for n in range(npages):
+            yield PageContext(self, n)
+
+
+class PageContext:
+    """Holds our context for a page
+
+    Must be pickable, so stores only intrinsic/simple data elements or those
+    capable of their serializing themselves via __getstate__.
     """
 
-    def __init__(self):
-        self.pdfinfo = None
-        self.options = None
-        self.work_folder = None
-        self.rotations = {}
+    def __init__(self, pdf_context: PdfContext, pageno):
+        self.work_folder = pdf_context.work_folder
+        self.origin = pdf_context.origin
+        self.options = pdf_context.options
+        self.pageno = pageno
+        self.pageinfo = pdf_context.pdfinfo[pageno]
+        self.plugin_manager = pdf_context.plugin_manager
 
-    def generate_pdfinfo(self, infile):
-        self.pdfinfo = PdfInfo(infile)
+    def get_path(self, name: str) -> Path:
+        return self.work_folder / ("%06d_%s" % (self.pageno + 1, name))
 
-    def get_pdfinfo(self):
-        "What we know about the input PDF"
-        return self.pdfinfo
+    def __getstate__(self):
+        state = self.__dict__.copy()
 
-    def set_pdfinfo(self, pdfinfo):
-        self.pdfinfo = pdfinfo
-
-    def get_options(self):
-        return self.options
-
-    def set_options(self, options):
-        self.options = options
-
-    def get_work_folder(self):
-        return self.work_folder
-
-    def set_work_folder(self, work_folder):
-        self.work_folder = work_folder
-
-    def get_rotation(self, pageno):
-        return self.rotations.get(pageno, 0)
-
-    def set_rotation(self, pageno, value):
-        self.rotations[pageno] = value
+        state['options'] = copy(self.options)
+        if not isinstance(state['options'].input_file, (str, bytes, os.PathLike)):
+            state['options'].input_file = 'stream'
+        if not isinstance(state['options'].output_file, (str, bytes, os.PathLike)):
+            state['options'].output_file = 'stream'
+        return state
 
 
-class JobContextManager(SyncManager):
-    pass
-
-
-def cleanup_working_files(work_folder, options):
+def cleanup_working_files(work_folder: Path, options: Namespace):
     if options.keep_temporary_files:
-        print(f"Temporary working files saved at:\n{work_folder}", file=sys.stderr)
+        print(f"Temporary working files retained at:\n{work_folder}", file=sys.stderr)
     else:
-        with suppress(FileNotFoundError):
-            shutil.rmtree(work_folder)
+        shutil.rmtree(work_folder, ignore_errors=True)

src/ocrmypdf/_logging.py

@@ -0,0 +1,60 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+import sys
+from contextlib import suppress
+
+from tqdm import tqdm
+
+
+class PageNumberFilter(logging.Filter):
+    def filter(self, record):
+        pageno = getattr(record, 'pageno', None)
+        if isinstance(pageno, int):
+            record.pageno = f'{pageno:5d} '
+        elif pageno is None:
+            record.pageno = ''
+        return True
+
+
+class TqdmConsole:
+    """Wrapper to log messages in a way that is compatible with tqdm progress bar
+
+    This routes log messages through tqdm so that it can print them above the
+    progress bar, and then refresh the progress bar, rather than overwriting
+    it which looks messy.
+
+    For some reason Python 3.6 prints extra empty messages from time to time,
+    so we suppress those.
+    """
+
+    def __init__(self, file):
+        self.file = file
+        self.py36 = sys.version_info[0:2] == (3, 6)
+
+    def write(self, msg):
+        # When no progress bar is active, tqdm.write() routes to print()
+        if self.py36:
+            if msg.strip() != '':
+                tqdm.write(msg.rstrip(), end='\n', file=self.file)
+        else:
+            tqdm.write(msg.rstrip(), end='\n', file=self.file)
+
+    def flush(self):
+        with suppress(AttributeError):
+            self.file.flush()

src/ocrmypdf/_plugin_manager.py

@@ -0,0 +1,113 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import argparse
+import importlib
+import importlib.util
+import sys
+from functools import partial
+from pathlib import Path
+from typing import Callable, List, Tuple, Union
+
+import pluggy
+
+from ocrmypdf import pluginspec
+from ocrmypdf.cli import get_parser, plugins_only_parser
+
+
+class OcrmypdfPluginManager(pluggy.PluginManager):
+    """pluggy.PluginManager that can fork.
+
+    Capable of reconstructing itself in child workers.
+
+    Arguments:
+        setup_func: callback that initializes the plugin manager with all
+            standard plugins
+    """
+
+    def __init__(
+        self, *args, setup_func: Callable[[pluggy.PluginManager], None], **kwargs
+    ):
+        self._init_args = args
+        self._setup_func = setup_func
+        self._init_kwargs = kwargs
+        super().__init__(*args, **kwargs)
+        setup_func(self)
+
+    def __getstate__(self):
+        state = dict(
+            _init_args=self._init_args,
+            _setup_func=self._setup_func,
+            _init_kwargs=self._init_kwargs,
+        )
+        return state
+
+    def __setstate__(self, state):
+        self.__init__(
+            *state['_init_args'],
+            setup_func=state['_setup_func'],
+            **state['_init_kwargs'],
+        )
+
+
+def _setup_plugins(
+    pm: pluggy.PluginManager, plugins: List[Union[str, Path]], builtins: bool = True
+):
+    pm.add_hookspecs(pluginspec)
+
+    all_plugins: List[Union[str, Path]] = []
+    if builtins:
+        all_plugins.extend(
+            [
+                'ocrmypdf.builtin_plugins.ghostscript',
+                'ocrmypdf.builtin_plugins.tesseract_ocr',
+            ]
+        )
+    all_plugins.extend(plugins)
+    for name in all_plugins:
+        if isinstance(name, Path) or name.endswith('.py'):
+            # Import by filename
+            module_name = Path(name).stem
+            spec = importlib.util.spec_from_file_location(module_name, name)
+            module = importlib.util.module_from_spec(spec)
+            sys.modules[module_name] = module
+            spec.loader.exec_module(module)
+        else:
+            # Import by dotted module name
+            module = importlib.import_module(name)
+        pm.register(module)
+
+
+def get_plugin_manager(plugins: List[str], builtins=True):
+    pm = OcrmypdfPluginManager(
+        project_name='ocrmypdf',
+        setup_func=partial(_setup_plugins, plugins=plugins, builtins=builtins),
+    )
+    return pm
+
+
+def get_parser_options_plugins(
+    args,
+) -> Tuple[argparse.ArgumentParser, argparse.Namespace, pluggy.PluginManager]:
+    pre_options, _unused = plugins_only_parser.parse_known_args(args=args)
+    plugin_manager = get_plugin_manager(pre_options.plugins)
+
+    parser = get_parser()
+    plugin_manager.hook.add_options(parser=parser)  # pylint: disable=no-member
+
+    options = parser.parse_args(args=args)
+    return parser, options, plugin_manager

src/ocrmypdf/_sync.py

@@ -0,0 +1,419 @@
+# © 2016 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+import logging.handlers
+import os
+import sys
+import threading
+from functools import partial
+from pathlib import Path
+from tempfile import mkdtemp
+from typing import List, NamedTuple, Optional, Tuple
+
+import pikepdf
+import PIL
+
+from ocrmypdf._concurrent import exec_progress_pool
+from ocrmypdf._graft import OcrGrafter
+from ocrmypdf._jobcontext import PageContext, PdfContext, cleanup_working_files
+from ocrmypdf._logging import PageNumberFilter
+from ocrmypdf._pipeline import (
+    convert_to_pdfa,
+    copy_final,
+    create_ocr_image,
+    create_pdf_page_from_image,
+    create_visible_page_jpg,
+    generate_postscript_stub,
+    get_orientation_correction,
+    get_pdfinfo,
+    is_ocr_required,
+    merge_sidecars,
+    metadata_fixup,
+    ocr_engine_hocr,
+    ocr_engine_textonly_pdf,
+    optimize_pdf,
+    preprocess_clean,
+    preprocess_deskew,
+    preprocess_remove_background,
+    rasterize,
+    rasterize_preview,
+    render_hocr_page,
+    should_visible_page_image_use_jpg,
+    triage,
+    validate_pdfinfo_options,
+)
+from ocrmypdf._plugin_manager import get_plugin_manager
+from ocrmypdf._validation import (
+    check_requested_output_file,
+    create_input_file,
+    report_output_file_size,
+)
+from ocrmypdf.exceptions import ExitCode, ExitCodeException
+from ocrmypdf.helpers import (
+    available_cpu_count,
+    check_pdf,
+    pikepdf_enable_mmap,
+    samefile,
+)
+from ocrmypdf.pdfa import file_claims_pdfa
+
+log = logging.getLogger(__name__)
+
+
+class PageResult(NamedTuple):
+    pageno: int
+    pdf_page_from_image: Optional[Path]
+    ocr: Optional[Path]
+    text: Optional[Path]
+    orientation_correction: int
+
+
+tls = threading.local()
+tls.pageno = None
+
+
+old_factory = logging.getLogRecordFactory()
+
+
+def record_factory(*args, **kwargs):
+    record = old_factory(*args, **kwargs)
+    if hasattr(tls, 'pageno'):
+        record.pageno = tls.pageno
+    return record
+
+
+logging.setLogRecordFactory(record_factory)
+
+
+def preprocess(
+    page_context: PageContext,
+    image: Path,
+    remove_background: bool,
+    deskew: bool,
+    clean: bool,
+) -> Path:
+    if remove_background:
+        image = preprocess_remove_background(image, page_context)
+    if deskew:
+        image = preprocess_deskew(image, page_context)
+    if clean:
+        image = preprocess_clean(image, page_context)
+    return image
+
+
+def make_intermediate_images(
+    page_context: PageContext, orientation_correction: int
+) -> Tuple[Path, Optional[Path]]:
+    options = page_context.options
+
+    ocr_image = preprocess_out = None
+    rasterize_out = rasterize(
+        page_context.origin,
+        page_context,
+        correction=orientation_correction,
+        remove_vectors=False,
+    )
+
+    if not any([options.clean, options.clean_final, options.remove_vectors]):
+        ocr_image = preprocess_out = preprocess(
+            page_context,
+            rasterize_out,
+            options.remove_background,
+            options.deskew,
+            clean=False,
+        )
+    else:
+        if not options.lossless_reconstruction:
+            preprocess_out = preprocess(
+                page_context,
+                rasterize_out,
+                options.remove_background,
+                options.deskew,
+                clean=options.clean_final,
+            )
+        if options.remove_vectors:
+            rasterize_ocr_out = rasterize(
+                page_context.origin,
+                page_context,
+                correction=orientation_correction,
+                remove_vectors=True,
+                output_tag='_ocr',
+            )
+        else:
+            rasterize_ocr_out = rasterize_out
+
+        if (
+            preprocess_out
+            and rasterize_ocr_out == rasterize_out
+            and options.clean == options.clean_final
+        ):
+            # Optimization: image for OCR is identical to presentation image
+            ocr_image = preprocess_out
+        else:
+            ocr_image = preprocess(
+                page_context,
+                rasterize_ocr_out,
+                options.remove_background,
+                options.deskew,
+                clean=options.clean,
+            )
+    return ocr_image, preprocess_out
+
+
+def exec_page_sync(page_context: PageContext):
+    options = page_context.options
+    tls.pageno = page_context.pageno + 1
+
+    if not is_ocr_required(page_context):
+        return PageResult(
+            pageno=page_context.pageno,
+            pdf_page_from_image=None,
+            ocr=None,
+            text=None,
+            orientation_correction=0,
+        )
+
+    orientation_correction = 0
+    if options.rotate_pages:
+        # Rasterize
+        rasterize_preview_out = rasterize_preview(page_context.origin, page_context)
+        orientation_correction = get_orientation_correction(
+            rasterize_preview_out, page_context
+        )
+
+    ocr_image, preprocess_out = make_intermediate_images(
+        page_context, orientation_correction
+    )
+    ocr_image_out = create_ocr_image(ocr_image, page_context)
+
+    pdf_page_from_image_out = None
+    if not options.lossless_reconstruction:
+        assert preprocess_out
+        visible_image_out = preprocess_out
+        if should_visible_page_image_use_jpg(page_context.pageinfo):
+            visible_image_out = create_visible_page_jpg(visible_image_out, page_context)
+        filtered_image = page_context.plugin_manager.hook.filter_page_image(
+            page=page_context, image_filename=visible_image_out
+        )
+        if filtered_image:
+            visible_image_out = filtered_image
+        pdf_page_from_image_out = create_pdf_page_from_image(
+            visible_image_out, page_context
+        )
+
+    if options.pdf_renderer == 'hocr':
+        (hocr_out, text_out) = ocr_engine_hocr(ocr_image_out, page_context)
+        ocr_out = render_hocr_page(hocr_out, page_context)
+
+    if options.pdf_renderer == 'sandwich':
+        (ocr_out, text_out) = ocr_engine_textonly_pdf(ocr_image_out, page_context)
+
+    return PageResult(
+        pageno=page_context.pageno,
+        pdf_page_from_image=pdf_page_from_image_out,
+        ocr=ocr_out,
+        text=text_out,
+        orientation_correction=orientation_correction,
+    )
+
+
+def post_process(pdf_file, context: PdfContext):
+    pdf_out = pdf_file
+    if context.options.output_type.startswith('pdfa'):
+        ps_stub_out = generate_postscript_stub(context)
+        pdf_out = convert_to_pdfa(pdf_out, ps_stub_out, context)
+
+    pdf_out = metadata_fixup(pdf_out, context)
+    return optimize_pdf(pdf_out, context)
+
+
+def worker_init(max_pixels: int):
+    # In Windows, child process will not inherit our change to this value in
+    # the parent process, so ensure workers get it set. Not needed when running
+    # threaded, but harmless to set again.
+    PIL.Image.MAX_IMAGE_PIXELS = max_pixels
+    pikepdf_enable_mmap()
+
+
+def exec_concurrent(context: PdfContext):
+    """Execute the pipeline concurrently"""
+
+    # Run exec_page_sync on every page context
+    max_workers = min(len(context.pdfinfo), context.options.jobs)
+    if max_workers > 1:
+        log.info("Start processing %d pages concurrently", max_workers)
+
+    sidecars: List[Optional[Path]] = [None] * len(context.pdfinfo)
+    ocrgraft = OcrGrafter(context)
+
+    def update_page(result: PageResult, pbar):
+        sidecars[result.pageno] = result.text
+        pbar.update()
+        ocrgraft.graft_page(
+            pageno=result.pageno,
+            image=result.pdf_page_from_image,
+            textpdf=result.ocr,
+            autorotate_correction=result.orientation_correction,
+        )
+        pbar.update()
+
+    exec_progress_pool(
+        use_threads=context.options.use_threads,
+        max_workers=max_workers,
+        tqdm_kwargs=dict(
+            total=(2 * len(context.pdfinfo)),
+            desc='OCR',
+            unit='page',
+            unit_scale=0.5,
+            disable=not context.options.progress_bar,
+        ),
+        task_initializer=partial(worker_init, PIL.Image.MAX_IMAGE_PIXELS),
+        task=exec_page_sync,
+        task_arguments=context.get_page_contexts(),
+        task_finished=update_page,
+    )
+
+    # Output sidecar text
+    if context.options.sidecar:
+        text = merge_sidecars(sidecars, context)
+        # Copy text file to destination
+        copy_final(text, context.options.sidecar, context)
+
+    # Merge layers to one single pdf
+    pdf = ocrgraft.finalize()
+
+    # PDF/A and metadata
+    pdf = post_process(pdf, context)
+
+    # Copy PDF file to destination
+    copy_final(pdf, context.options.output_file, context)
+
+
+class NeverRaise(Exception):
+    """An exception that is never raised"""
+
+    pass  # pylint: disable=unnecessary-pass
+
+
+def configure_debug_logging(log_filename, prefix=''):
+    log_file_handler = logging.FileHandler(log_filename, delay=True)
+    log_file_handler.setLevel(logging.DEBUG)
+    formatter = logging.Formatter(
+        '[%(asctime)s] - %(name)s - %(levelname)7s -%(pageno)s %(message)s'
+    )
+    log_file_handler.setFormatter(formatter)
+    log_file_handler.addFilter(PageNumberFilter())
+    logging.getLogger(prefix).addHandler(log_file_handler)
+    return log_file_handler
+
+
+def run_pipeline(options, *, plugin_manager, api=False):
+    # Any changes to options will not take effect for options that are already
+    # bound to function parameters in the pipeline. (For example
+    # options.input_file, options.pdf_renderer are already bound.)
+    if not options.jobs:
+        options.jobs = available_cpu_count()
+    if not plugin_manager:
+        plugin_manager = get_plugin_manager(options.plugins)
+
+    work_folder = Path(mkdtemp(prefix="com.github.ocrmypdf."))
+    debug_log_handler = None
+    if (options.keep_temporary_files or options.verbose >= 1) and not os.environ.get(
+        'PYTEST_CURRENT_TEST', ''
+    ):
+        debug_log_handler = configure_debug_logging(Path(work_folder) / "debug.log")
+
+    pikepdf_enable_mmap()
+
+    try:
+        check_requested_output_file(options)
+        start_input_file, original_filename = create_input_file(options, work_folder)
+
+        # Triage image or pdf
+        origin_pdf = triage(
+            original_filename, start_input_file, work_folder / 'origin.pdf', options
+        )
+
+        # Gather pdfinfo and create context
+        pdfinfo = get_pdfinfo(
+            origin_pdf,
+            detailed_analysis=options.redo_ocr,
+            progbar=options.progress_bar,
+            max_workers=options.jobs if not options.use_threads else 1,  # To help debug
+            check_pages=options.pages,
+        )
+
+        context = PdfContext(options, work_folder, origin_pdf, pdfinfo, plugin_manager)
+
+        # Validate options are okay for this pdf
+        validate_pdfinfo_options(context)
+
+        # Execute the pipeline
+        exec_concurrent(context)
+
+        if options.output_file == '-':
+            log.info("Output sent to stdout")
+        elif (
+            hasattr(options.output_file, 'writable') and options.output_file.writable()
+        ):
+            log.info("Output written to stream")
+        elif samefile(options.output_file, os.devnull):
+            pass  # Say nothing when sending to dev null
+        else:
+            if options.output_type.startswith('pdfa'):
+                pdfa_info = file_claims_pdfa(options.output_file)
+                if pdfa_info['pass']:
+                    log.info(
+                        "Output file is a %s (as expected)", pdfa_info['conformance']
+                    )
+                else:
+                    log.warning(
+                        "Output file is okay but is not PDF/A (seems to be %s)",
+                        pdfa_info['conformance'],
+                    )
+                    return ExitCode.pdfa_conversion_failed
+            if not check_pdf(options.output_file):
+                log.warning('Output file: The generated PDF is INVALID')
+                return ExitCode.invalid_output_pdf
+            report_output_file_size(options, start_input_file, options.output_file)
+
+    except (KeyboardInterrupt if not api else NeverRaise) as e:
+        if options.verbose >= 1:
+            log.exception("KeyboardInterrupt")
+        else:
+            log.error("KeyboardInterrupt")
+        return ExitCode.ctrl_c
+    except (ExitCodeException if not api else NeverRaise) as e:
+        if str(e):
+            log.error("%s: %s", type(e).__name__, str(e))
+        else:
+            log.error(type(e).__name__)
+        return e.exit_code
+    except (Exception if not api else NeverRaise) as e:  # pylint: disable=broad-except
+        log.exception("An exception occurred while executing the pipeline")
+        return ExitCode.other_error
+    finally:
+        if debug_log_handler:
+            try:
+                debug_log_handler.close()
+                log.removeHandler(debug_log_handler)
+            except EnvironmentError as e:
+                print(e, file=sys.stderr)
+        cleanup_working_files(work_folder, options)
+
+    return ExitCode.ok

src/ocrmypdf/_validation.py

@@ -0,0 +1,432 @@
+#!/usr/bin/env python3
+# © 2015-17 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import locale
+import logging
+import os
+import sys
+import unicodedata
+from pathlib import Path
+from shutil import copyfileobj
+from typing import Tuple
+
+import pikepdf
+import PIL
+
+from ocrmypdf._exec import jbig2enc, pngquant, unpaper
+from ocrmypdf._unicodefun import verify_python3_env
+from ocrmypdf.exceptions import (
+    BadArgsError,
+    InputFileError,
+    MissingDependencyError,
+    OutputFileAccessError,
+)
+from ocrmypdf.helpers import (
+    is_file_writable,
+    is_iterable_notstr,
+    monotonic,
+    safe_symlink,
+)
+from ocrmypdf.subprocess import check_external_program
+
+# -------------
+# External dependencies
+
+HOCR_OK_LANGS = frozenset(['eng', 'deu', 'spa', 'ita', 'por'])
+DEFAULT_LANGUAGE = 'eng'  # Enforce English hegemony
+
+log = logging.getLogger(__name__)
+
+
+# --------
+# Critical environment tests
+verify_python3_env()
+
+
+def check_platform():
+    if os.name == 'nt' and sys.maxsize <= 2 ** 32:  # pragma: no cover
+        # 32-bit interpreter on Windows
+        log.error(
+            "You are running OCRmyPDF in a 32-bit (x86) Python interpreter."
+            "Please use a 64-bit (x86-64) version of Python."
+        )
+
+
+def check_options_languages(options, ocr_engine_languages):
+    if not options.languages:
+        options.languages = {DEFAULT_LANGUAGE}
+        system_lang = locale.getlocale()[0]
+        if system_lang and not system_lang.startswith('en'):
+            log.debug("No language specified; assuming --language %s", DEFAULT_LANGUAGE)
+    if not ocr_engine_languages:
+        return
+    if not options.languages.issubset(ocr_engine_languages):
+        msg = (
+            f"OCR engine does not have language data for the following "
+            "requested languages: \n"
+        )
+        for lang in options.languages - ocr_engine_languages:
+            msg += lang + '\n'
+        raise MissingDependencyError(msg)
+
+
+def check_options_output(options):
+    is_latin = options.languages.issubset(HOCR_OK_LANGS)
+
+    if options.pdf_renderer == 'hocr' and not is_latin:
+        msg = (
+            "The 'hocr' PDF renderer is known to cause problems with one "
+            "or more of the languages in your document.  Use "
+            "--pdf-renderer auto (the default) to avoid this issue."
+        )
+        log.warning(msg)
+
+    lossless_reconstruction = False
+    if not any(
+        (
+            options.deskew,
+            options.clean_final,
+            options.force_ocr,
+            options.remove_background,
+        )
+    ):
+        lossless_reconstruction = True
+    options.lossless_reconstruction = lossless_reconstruction
+
+    if not options.lossless_reconstruction and options.redo_ocr:
+        raise BadArgsError(
+            "--redo-ocr is not currently compatible with --deskew, "
+            "--clean-final, and --remove-background"
+        )
+
+
+def check_options_sidecar(options):
+    if options.sidecar == '\0':
+        if options.output_file == '-':
+            raise BadArgsError(
+                "--sidecar filename must be specified when output file is stdout."
+            )
+        options.sidecar = options.output_file + '.txt'
+
+
+def check_options_preprocessing(options):
+    if options.clean_final:
+        options.clean = True
+    if options.unpaper_args and not options.clean:
+        raise BadArgsError("--clean is required for --unpaper-args")
+    if options.clean:
+        check_external_program(
+            program='unpaper',
+            package='unpaper',
+            version_checker=unpaper.version,
+            need_version='6.1',
+            required_for=['--clean, --clean-final'],
+        )
+        try:
+            if options.unpaper_args:
+                options.unpaper_args = unpaper.validate_custom_args(
+                    options.unpaper_args
+                )
+        except Exception as e:
+            raise BadArgsError(str(e))
+
+
+def _pages_from_ranges(ranges):
+    if is_iterable_notstr(ranges):
+        return set(ranges)
+    pages = []
+    page_groups = ranges.replace(' ', '').split(',')
+    for g in page_groups:
+        if not g:
+            continue
+        try:
+            start, end = g.split('-')
+        except ValueError:
+            pages.append(int(g) - 1)
+        else:
+            try:
+                pages.extend(range(int(start) - 1, int(end)))
+            except ValueError:
+                raise BadArgsError("invalid page range")
+
+    if not monotonic(pages):
+        log.warning(
+            "List of pages to process contains duplicate pages, or pages that are "
+            "out of order"
+        )
+    if any(page < 0 for page in pages):
+        raise BadArgsError("pages refers to a page number less than 1")
+
+    log.debug("OCRing only these pages: %s", pages)
+    return set(pages)
+
+
+def check_options_ocr_behavior(options):
+    exclusive_options = sum(
+        [
+            (1 if opt else 0)
+            for opt in (options.force_ocr, options.skip_text, options.redo_ocr)
+        ]
+    )
+    if exclusive_options >= 2:
+        raise BadArgsError("Choose only one of --force-ocr, --skip-text, --redo-ocr.")
+    if options.pages and options.sidecar:
+        raise BadArgsError("--pages and --sidecar are mutually exclusive")
+    if options.pages:
+        options.pages = _pages_from_ranges(options.pages)
+
+
+def check_options_optimizing(options):
+    if options.optimize >= 2:
+        check_external_program(
+            program='pngquant',
+            package='pngquant',
+            version_checker=pngquant.version,
+            need_version='2.0.1',
+            required_for='--optimize {2,3}',
+        )
+
+    if options.optimize >= 2:
+        # Although we use JBIG2 for optimize=1, don't nag about it unless the
+        # user is asking for more optimization
+        check_external_program(
+            program='jbig2',
+            package='jbig2enc',
+            version_checker=jbig2enc.version,
+            need_version='0.28',
+            required_for='--optimize {2,3} | --jbig2-lossy',
+            recommended=True if not options.jbig2_lossy else False,
+        )
+
+    if options.optimize == 0 and any(
+        [options.jbig2_lossy, options.png_quality, options.jpeg_quality]
+    ):
+        log.warning(
+            "The arguments --jbig2-lossy, --png-quality, and --jpeg-quality "
+            "will be ignored because --optimize=0."
+        )
+
+
+def check_options_advanced(options):
+    if options.pdfa_image_compression != 'auto' and options.output_type.startswith(
+        'pdfa'
+    ):
+        log.warning(
+            "--pdfa-image-compression argument has no effect when "
+            "--output-type is not 'pdfa', 'pdfa-1', or 'pdfa-2'"
+        )
+
+
+def check_options_metadata(options):
+    docinfo = [options.title, options.author, options.keywords, options.subject]
+    for s in (m for m in docinfo if m):
+        for c in s:
+            if unicodedata.category(c) == 'Co' or ord(c) >= 0x10000:
+                raise ValueError(
+                    "One of the metadata strings contains "
+                    "an unsupported Unicode character: '{}' (U+{})".format(
+                        c, hex(ord(c))[2:].upper()
+                    )
+                )
+
+
+def check_options_pillow(options):
+    PIL.Image.MAX_IMAGE_PIXELS = int(options.max_image_mpixels * 1_000_000)
+    if PIL.Image.MAX_IMAGE_PIXELS == 0:
+        PIL.Image.MAX_IMAGE_PIXELS = None
+
+
+def _check_options(options, plugin_manager, ocr_engine_languages):
+    check_platform()
+    check_options_languages(options, ocr_engine_languages)
+    check_options_metadata(options)
+    check_options_output(options)
+    check_options_sidecar(options)
+    check_options_preprocessing(options)
+    check_options_ocr_behavior(options)
+    check_options_optimizing(options)
+    check_options_advanced(options)
+    check_options_pillow(options)
+    plugin_manager.hook.check_options(options=options)
+
+
+def check_options(options, plugin_manager):
+    ocr_engine_languages = plugin_manager.hook.get_ocr_engine().languages(options)
+    _check_options(options, plugin_manager, ocr_engine_languages)
+
+
+def check_closed_streams(options):  # pragma: no cover
+    """Work around Python issue with multiprocessing forking on closed streams
+
+    https://bugs.python.org/issue28326
+
+    Attempting to a fork/exec a new Python process when any of std{in,out,err}
+    are closed or not flushable for some reason may raise an exception.
+    Fix this by opening devnull if the handle seems to be closed.  Do this
+    globally to avoid tracking places all places that fork.
+
+    Seems to be specific to multiprocessing.Process not all Python process
+    forkers.
+
+    The error actually occurs when the stream object is not flushable,
+    but replacing an open stream object that is not flushable with
+    /dev/null is a bad idea since it will create a silent failure.  Replacing
+    a closed handle with /dev/null seems safe.
+
+    """
+
+    if sys.version_info[0:3] >= (3, 6, 4):
+        return True  # Issued fixed in Python 3.6.4+
+
+    if sys.stderr is None:
+        sys.stderr = open(os.devnull, 'w')
+
+    if sys.stdin is None:
+        if options.input_file == '-':
+            log.error("Trying to read from stdin but stdin seems closed")
+            return False
+        sys.stdin = open(os.devnull, 'r')
+
+    if sys.stdout is None:
+        if options.output_file == '-':
+            # Can't replace stdout if the user is piping
+            # If this case can even happen, it must be some kind of weird
+            # stream.
+            log.error(
+                "Output was set to stdout '-' but the stream attached to "
+                "stdout does not support the flush() system call.  This "
+                "will fail."
+            )
+            return False
+        sys.stdout = open(os.devnull, 'w')
+
+    return True
+
+
+def log_page_orientations(pdfinfo):
+    direction = {0: 'n', 90: 'e', 180: 's', 270: 'w'}
+    orientations = []
+    for n, page in enumerate(pdfinfo):
+        angle = page.rotation or 0
+        if angle != 0:
+            orientations.append('{0}{1}'.format(n + 1, direction.get(angle, '')))
+    if orientations:
+        log.info('Page orientations detected: %s', ' '.join(orientations))
+
+
+def create_input_file(options, work_folder: Path) -> Tuple[Path, str]:
+    if options.input_file == '-':
+        # stdin
+        log.info('reading file from standard input')
+        target = work_folder / 'stdin'
+        with open(target, 'wb') as stream_buffer:
+            copyfileobj(sys.stdin.buffer, stream_buffer)
+        return target, "stdin"
+    elif hasattr(options.input_file, 'readable'):
+        if not options.input_file.readable():
+            raise InputFileError("Input file stream is not readable")
+        log.info('reading file from input stream')
+        target = work_folder / 'stream'
+        with open(target, 'wb') as stream_buffer:
+            copyfileobj(options.input_file, stream_buffer)
+        return target, "stream"
+    else:
+        try:
+            target = work_folder / 'origin'
+            safe_symlink(options.input_file, target)
+            return target, os.fspath(options.input_file)
+        except FileNotFoundError:
+            raise InputFileError(f"File not found - {options.input_file}")
+
+
+def check_requested_output_file(options):
+    if options.output_file == '-':
+        if sys.stdout.isatty():
+            raise BadArgsError(
+                "Output was set to stdout '-' but it looks like stdout "
+                "is connected to a terminal.  Please redirect stdout to a "
+                "file."
+            )
+    elif hasattr(options.output_file, 'writable'):
+        if not options.output_file.writable():
+            raise OutputFileAccessError("Output stream is not writable")
+    elif not is_file_writable(options.output_file):
+        raise OutputFileAccessError(
+            f"Output file location ({options.output_file}) is not a writable file."
+        )
+
+
+def report_output_file_size(options, input_file, output_file):
+    try:
+        output_size = Path(output_file).stat().st_size
+        input_size = Path(input_file).stat().st_size
+    except FileNotFoundError:
+        return  # Outputting to stream or something
+    with pikepdf.open(output_file) as p:
+        # Overhead constants obtained by estimating amount of data added by OCR
+        # PDF/A conversion, and possible XMP metadata addition, with compression
+        FILE_OVERHEAD = 4000
+        OCR_PER_PAGE_OVERHEAD = 3000
+        reasonable_overhead = FILE_OVERHEAD + OCR_PER_PAGE_OVERHEAD * len(p.pages)
+    ratio = output_size / input_size
+    reasonable_ratio = output_size / (input_size + reasonable_overhead)
+    if reasonable_ratio < 1.35 or input_size < 25000:
+        return  # Seems fine
+
+    reasons = []
+    image_preproc = {
+        'deskew',
+        'clean_final',
+        'remove_background',
+        'oversample',
+        'force_ocr',
+    }
+    for arg in image_preproc:
+        if getattr(options, arg, False):
+            reasons.append(
+                f"The argument --{arg.replace('_', '-')} was issued, causing transcoding."
+            )
+
+    if options.optimize == 0:
+        reasons.append("Optimization was disabled.")
+    else:
+        image_optimizers = {
+            'jbig2': jbig2enc.available(),
+            'pngquant': pngquant.available(),
+        }
+        for name, available in image_optimizers.items():
+            if not available:
+                reasons.append(
+                    f"The optional dependency '{name}' was not found, so some image "
+                    f"optimizations could not be attempted."
+                )
+    if options.output_type.startswith('pdfa'):
+        reasons.append("PDF/A conversion was enabled. (Try `--output-type pdf`.)")
+    if options.plugins:
+        reasons.append("Plugins were used.")
+
+    if reasons:
+        explanation = "Possible reasons for this include:\n" + '\n'.join(reasons) + "\n"
+    else:
+        explanation = "No reason for this increase is known.  Please report this issue."
+
+    log.warning(
+        f"The output file size is {ratio:.2f}× larger than the input file.\n"
+        f"{explanation}"
+    )

src/ocrmypdf/_version.py

@@ -0,0 +1,24 @@
+# © 2017 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import pkg_resources
+
+PROGRAM_NAME = 'ocrmypdf'
+
+# Official PEP 396
+__version__ = pkg_resources.get_distribution('ocrmypdf').version

src/ocrmypdf/_weave.py

@@ -1,419 +0,0 @@
-# © 2018 James R. Barlow: github.com/jbarlow83
-#
-# This file is part of OCRmyPDF.
-#
-# OCRmyPDF is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# OCRmyPDF is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
-
-from itertools import groupby
-from pathlib import Path
-import os
-
-import pikepdf
-
-from .exec import tesseract
-from .helpers import flatten_groups, page_number
-
-
-MAX_OPEN_PAGE_PDFS = int(os.environ.get('_OCRMYPDF_MAX_OPEN_PAGE_PDFS', 100))
-
-
-def _update_page_resources(*, page, font, font_key, procset):
-    """Update this page's fonts with a reference to the Glyphless font"""
-
-    if '/Resources' not in page:
-        page['/Resources'] = pikepdf.Dictionary({})
-    resources = page['/Resources']
-    try:
-        fonts = resources['/Font']
-    except KeyError:
-        fonts = pikepdf.Dictionary({})
-    if font_key is not None and font_key not in fonts:
-        fonts[font_key] = font
-    resources['/Font'] = fonts
-
-    # Reassign /ProcSet to one that just lists everything - ProcSet is
-    # obsolete and doesn't matter but recommended for old viewer support
-    resources['/ProcSet'] = procset
-
-
-def strip_invisible_text(pdf, page, log):
-    stream = []
-    in_text_obj = False
-    render_mode = 0
-    text_objects = []
-
-    page.page_contents_coalesce()
-    for operands, operator in pikepdf.parse_content_stream(page, ''):
-        if not in_text_obj:
-            if operator == pikepdf.Operator('BT'):
-                in_text_obj = True
-                render_mode = 0
-                text_objects.append((operands, operator))
-            else:
-                stream.append((operands, operator))
-        else:
-            if operator == pikepdf.Operator('Tr'):
-                render_mode = operands[0]
-            text_objects.append((operands, operator))
-            if operator == pikepdf.Operator('ET'):
-                in_text_obj = False
-                if render_mode != 3:
-                    stream.extend(text_objects)
-                text_objects.clear()
-
-    def convert(op):
-        try:
-            return op.unparse()
-        except AttributeError:
-            return str(op).encode('ascii')
-
-    lines = []
-
-    for operands, operator in stream:
-        if operator == pikepdf.Operator('INLINE IMAGE'):
-            iim = operands[0]
-            line = iim.unparse()
-        else:
-            line = b' '.join(convert(op) for op in operands) + b' ' + operator.unparse()
-        lines.append(line)
-
-    content_stream = b'\n'.join(lines)
-    page.Contents = pikepdf.Stream(pdf, content_stream)
-
-
-def _weave_layers_graft(
-    *, pdf_base, page_num, text, font, font_key, procset, rotation, strip_old_text, log
-):
-    """Insert the text layer from text page 0 on to pdf_base at page_num"""
-
-    log.debug("Grafting")
-    if Path(text).stat().st_size == 0:
-        return
-
-    # This is a pointer indicating a specific page in the base file
-    pdf_text = pikepdf.open(text)
-    pdf_text_contents = pdf_text.pages[0].Contents.read_bytes()
-
-    if not tesseract.has_textonly_pdf():
-        # If we don't have textonly_pdf, edit the stream to delete the
-        # instruction to draw the image Tesseract generated, which we do not
-        # use.
-        stream = bytearray(pdf_text_contents)
-        pattern = b'/Im1 Do'
-        idx = stream.find(pattern)
-        stream[idx : (idx + len(pattern))] = b' ' * len(pattern)
-        pdf_text_contents = bytes(stream)
-
-    base_page = pdf_base.pages.p(page_num)
-
-    # The text page always will be oriented up by this stage but the original
-    # content may have a rotation applied. Wrap the text stream with a rotation
-    # so it will be oriented the same way as the rest of the page content.
-    # (Previous versions OCRmyPDF rotated the content layer to match the text.)
-    mediabox = [float(pdf_text.pages[0].MediaBox[v]) for v in range(4)]
-    wt, ht = mediabox[2] - mediabox[0], mediabox[3] - mediabox[1]
-
-    mediabox = [float(base_page.MediaBox[v]) for v in range(4)]
-    wp, hp = mediabox[2] - mediabox[0], mediabox[3] - mediabox[1]
-
-    translate = pikepdf.PdfMatrix().translated(-wt / 2, -ht / 2)
-    untranslate = pikepdf.PdfMatrix().translated(wp / 2, hp / 2)
-    # -rotation because the input is a clockwise angle and this formula
-    # uses CCW
-    rotation = -rotation % 360
-    rotate = pikepdf.PdfMatrix().rotated(rotation)
-
-    # Because of rounding of DPI, we might get a text layer that is not
-    # identically sized to the target page. Scale to adjust. Normally this
-    # is within 0.998.
-    if rotation in (90, 270):
-        wt, ht = ht, wt
-    scale_x = wp / wt
-    scale_y = hp / ht
-
-    log.debug('%r', (scale_x, scale_y))
-    scale = pikepdf.PdfMatrix().scaled(scale_x, scale_y)
-
-    # Translate the text so it is centered at (0, 0), rotate it there, adjust
-    # for a size different between initial and text PDF, then untranslate
-    ctm = translate @ rotate @ scale @ untranslate
-
-    pdf_text_contents = b'q %s cm\n' % ctm.encode() + pdf_text_contents + b'\nQ\n'
-
-    new_text_layer = pikepdf.Stream(pdf_base, pdf_text_contents)
-
-    if strip_old_text:
-        strip_invisible_text(pdf_base, base_page, log)
-
-    base_page.page_contents_add(new_text_layer, prepend=True)
-
-    _update_page_resources(
-        page=base_page, font=font, font_key=font_key, procset=procset
-    )
-
-
-def _find_font(text, pdf_base):
-    """Copy a font from the filename text into pdf_base"""
-
-    font, font_key = None, None
-    possible_font_names = ('/f-0-0', '/F1')
-    try:
-        pdf_text = pikepdf.open(text)
-        pdf_text_fonts = pdf_text.pages[0].Resources.get('/Font', {})
-    except Exception:
-        return None, None
-
-    for f in possible_font_names:
-        pdf_text_font = pdf_text_fonts.get(f, None)
-        if pdf_text_font is not None:
-            font_key = f
-            break
-    if pdf_text_font:
-        font = pdf_base.copy_foreign(pdf_text_font)
-    return font, font_key
-
-
-def _traverse_toc(pdf_base, visitor_fn, log):
-    """
-    Walk the table of contents, calling visitor_fn() at each node
-
-    The /Outlines data structure is a messy data structure, but rather than
-    navigating hierarchically we just track unique nodes.  Enqueue nodes when
-    we find them, and never visit them again.  set() is awesome.  We look for
-    the two types of object in the table of contents that can be page bookmarks
-    and update the page entry.
-
-    """
-
-    visited = set()
-    queue = set()
-    link_keys = ('/Parent', '/First', '/Last', '/Prev', '/Next')
-
-    if not '/Outlines' in pdf_base.root:
-        return
-
-    queue.add(pdf_base.root.Outlines.objgen)
-    while queue:
-        objgen = queue.pop()
-        visited.add(objgen)
-        node = pdf_base.get_object(objgen)
-        log.debug('fix toc: exploring outline entries at %r', objgen)
-
-        # Enumerate other nodes we could visit from here
-        for key in link_keys:
-            if key not in node:
-                continue
-            item = node[key]
-            if not item.is_indirect:
-                # Direct references are not allowed here, but it's not clear
-                # what we should do if we find any. Removing them is an option:
-                # node[key] = pdf_base.make_indirect(None)
-                continue
-            objgen = item.objgen
-            if objgen not in visited:
-                queue.add(objgen)
-
-        if visitor_fn:
-            visitor_fn(pdf_base, node, log)
-
-
-def _fix_toc(pdf_base, pageref_remap, log):
-    """Repair the table of contents
-
-    Whenever we replace a page wholesale, it gets assigned a new objgen number
-    and other references to it within the PDF become invalid, most notably in
-    the table of contents (/Outlines in PDF-speak).  In weave_layers we collect
-    pageref_remap, a mapping that describes the new objgen number given an old
-    one.  (objgen is a tuple, and the gen is almost always zero.)
-
-    It may ultimately be better to find a way to rebuild a page in place.
-
-    """
-
-    if not pageref_remap:
-        return
-
-    def remap_dest(dest_node):
-        """
-        Inner helper function: change the objgen for any page from the old we
-        invalidated to its new one.
-        """
-        try:
-            pageref = dest_node[0]
-            if pageref['/Type'] == '/Page' and pageref.objgen in pageref_remap:
-                new_objgen = pageref_remap[pageref.objgen]
-                dest_node[0] = pdf_base.get_object(new_objgen)
-        except (IndexError, TypeError) as e:
-            log.warning("This file may contain invalid table of contents entries")
-            log.debug(e)
-
-    def visit_remap_dest(pdf_base, node, log):
-        """
-        Visitor function to fix ToC entries
-
-        Test for the two types of references to pages that can occur in ToCs.
-        Both types have the same final format (an indirect reference to the
-        target page).
-        """
-        if '/Dest' in node:
-            # /Dest reference to another page (old method)
-            remap_dest(node['/Dest'])
-        elif '/A' in node:
-            # /A (action) command set to "GoTo" (newer method)
-            if '/S' in node['/A'] and node['/A']['/S'] == '/GoTo':
-                remap_dest(node['/A']['/D'])
-
-    _traverse_toc(pdf_base, visit_remap_dest, log)
-
-
-def weave_layers(infiles, output_file, log, context):
-    """Apply text layer and/or image layer changes to baseline file
-
-    This is where the magic happens. infiles will be the main PDF to modify,
-    and optional .text.pdf and .image-layer.pdf files, organized however ruffus
-    organizes them.
-
-    From .text.pdf, we copy the content stream (which contains the Tesseract
-    OCR results), and rotate it into place. The first time we do this, we also
-    copy the GlyphlessFont, and then reference that font again.
-
-    For .image-layer.pdf, we check if this is a "pointer" to the original file,
-    or a new file. If a new file, we replace the page and remember that we
-    replaced this page.
-
-    Every 100 open files, we save intermediate results, to avoid any resource
-    limits, since pikepdf/qpdf need to keep a lot of open file handles in the
-    background. When objects are copied from one file to another qpdf, qpdf
-    doesn't actually copy the data until asked to write, so all the resources
-    it may need to remain available.
-
-    For completeness, we set up a /ProcSet on every page, although it's
-    unlikely any PDF viewer cares about this anymore.
-
-    """
-
-    def input_sorter(key):
-        try:
-            return page_number(key)
-        except ValueError:
-            return -1
-
-    flat_inputs = sorted(flatten_groups(infiles), key=input_sorter)
-    groups = groupby(flat_inputs, key=input_sorter)
-
-    # Extract first item
-    _, basegroup = next(groups)
-    base = list(basegroup)[0]
-    path_base = Path(base).resolve()
-    pdf_base = pikepdf.open(path_base)
-    keep_open = []
-    font, font_key, procset = None, None, None
-    pdfinfo = context.get_pdfinfo()
-    pagerefs = {}
-
-    # Walk the table of contents first, to trigger pikepdf/qpdf to resolve all
-    # page references in the table of contents. Some PDF generators put invalid
-    # references in the ToC, so we want to resolve them to null before we
-    # create any references, or the ToC will be corrupted
-    _traverse_toc(pdf_base, None, log)
-
-    procset = pdf_base.make_indirect(
-        pikepdf.Object.parse(b'[ /PDF /Text /ImageB /ImageC /ImageI ]')
-    )
-
-    # Iterate rest
-    for page_num, layers in groups:
-        layers = list(layers)
-        log.debug(page_num)
-        log.debug(layers)
-
-        text = next((ii for ii in layers if ii.endswith('.text.pdf')), None)
-        image = next((ii for ii in layers if ii.endswith('.image-layer.pdf')), None)
-
-        if text and not font:
-            font, font_key = _find_font(text, pdf_base)
-
-        replacing = False
-        content_rotation = pdfinfo[page_num - 1].rotation
-
-        path_image = Path(image).resolve() if image else None
-        if path_image is not None and path_image != path_base:
-            # We are replacing the old page with a rasterized PDF of the new
-            # page
-            log.debug("Replace")
-            old_objgen = pdf_base.pages[page_num - 1].objgen
-
-            pdf_image = pikepdf.open(image)
-            keep_open.append(pdf_image)
-            image_page = pdf_image.pages[0]
-            pdf_base.pages[page_num - 1] = image_page
-
-            # We're adding a new page, which will get a new objgen number pair,
-            # so we need to update any references to it.  qpdf did not like
-            # my attempt to update the old object in place, but that is an
-            # option to consider
-            pagerefs[old_objgen] = pdf_base.pages[page_num - 1].objgen
-            replacing = True
-
-        autorotate_correction = context.get_rotation(page_num - 1)
-        if replacing:
-            content_rotation = autorotate_correction
-        text_rotation = autorotate_correction
-        text_misaligned = (text_rotation - content_rotation) % 360
-        log.debug(
-            '%r',
-            [text_rotation, autorotate_correction, text_misaligned, content_rotation],
-        )
-
-        if text and font:
-            # Graft the text layer onto this page, whether new or old
-            strip_old = context.get_options().redo_ocr
-            _weave_layers_graft(
-                pdf_base=pdf_base,
-                page_num=page_num,
-                text=text,
-                font=font,
-                font_key=font_key,
-                rotation=text_misaligned,
-                procset=procset,
-                strip_old_text=strip_old,
-                log=log,
-            )
-
-        # Correct the rotation if applicable
-        pdf_base.pages[page_num - 1].Rotate = (
-            content_rotation - autorotate_correction
-        ) % 360
-
-        if len(keep_open) > MAX_OPEN_PAGE_PDFS:
-            # qpdf limitations require us to keep files open when we intend
-            # to copy content from them before saving. However, we want to keep
-            # a lid on file handles and memory usage, so for big files we're
-            # going to stop and save periodically. Attach the font to page 1
-            # even if page 1 doesn't use it, so we have a way to get it back.
-            page0 = pdf_base.pages[0]
-            _update_page_resources(
-                page=page0, font=font, font_key=font_key, procset=procset
-            )
-            interim = output_file + f'_working{page_num}.pdf'
-            pdf_base.save(interim)
-            del pdf_base
-            keep_open = []
-
-            pdf_base = pikepdf.open(interim)
-            procset = pdf_base.pages[0].Resources.ProcSet
-            font, font_key = None, None  # Reacquire this information
-
-    _fix_toc(pdf_base, pagerefs, log)
-    pdf_base.save(output_file)

src/ocrmypdf/api.py

@@ -0,0 +1,307 @@
+# © 2019 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+import os
+import sys
+from enum import IntEnum
+from pathlib import Path
+from typing import BinaryIO, Iterable, Union
+
+from ocrmypdf._logging import PageNumberFilter, TqdmConsole
+from ocrmypdf._plugin_manager import get_plugin_manager
+from ocrmypdf._sync import run_pipeline
+from ocrmypdf._validation import check_options
+from ocrmypdf.cli import ArgumentParser, get_parser
+from ocrmypdf.helpers import is_iterable_notstr
+
+try:
+    import coloredlogs
+except ModuleNotFoundError:
+    coloredlogs = None
+
+
+PathOrIO = Union[BinaryIO, os.PathLike, str, bytes]
+
+
+class Verbosity(IntEnum):
+    """Verbosity level for configure_logging."""
+
+    quiet = -1  #: Suppress most messages
+    default = 0  #: Default level of logging
+    debug = 1  #: Output ocrmypdf debug messages
+    debug_all = 2  #: More detailed debugging from ocrmypdf and dependent modules
+
+
+def configure_logging(
+    verbosity: Verbosity,
+    progress_bar_friendly: bool = True,
+    manage_root_logger: bool = False,
+):
+    """Set up logging.
+
+    Library users may wish to use this function if they want their log output to be
+    similar to ocrmypdf command line interface. If not used, the external application
+    should configure logging on its own.
+
+    ocrmypdf will perform all of its logging under the ``"ocrmypdf"`` logging namespace.
+    In addition, ocrmypdf imports pdfminer, which logs under ``"pdfminer"``. A library
+    user may wish to configure both; note that pdfminer is extremely chatty at the log
+    level ``logging.INFO``.
+
+    Library users may perform additional configuration afterwards.
+
+    Args:
+        verbosity (Verbosity): Verbosity level.
+        progress_bar_friendly (bool): Install the TqdmConsole log handler, which is
+            compatible with the tqdm progress bar; without this log messages will
+            overwrite the progress bar
+        manage_root_logger (bool): Configure the process's root logger, to ensure
+            all log output is sent through
+
+    Returns:
+        The toplevel logger for ocrmypdf (or the root logger, if we are managing it).
+    """
+
+    prefix = '' if manage_root_logger else 'ocrmypdf'
+
+    log = logging.getLogger(prefix)
+    log.setLevel(logging.DEBUG)
+
+    if progress_bar_friendly:
+        console = logging.StreamHandler(stream=TqdmConsole(sys.stderr))
+    else:
+        console = logging.StreamHandler(stream=sys.stderr)
+
+    if verbosity < 0:
+        console.setLevel(logging.ERROR)
+    elif verbosity >= 1:
+        console.setLevel(logging.DEBUG)
+    else:
+        console.setLevel(logging.INFO)
+
+    console.addFilter(PageNumberFilter())
+
+    if verbosity >= 2:
+        fmt = '%(levelname)7s %(name)s -%(pageno)s %(message)s'
+    else:
+        fmt = '%(pageno)s%(message)s'
+
+    use_colors = progress_bar_friendly
+    if not coloredlogs:
+        use_colors = False
+    if use_colors:
+        if os.name == 'nt':
+            use_colors = coloredlogs.enable_ansi_support()
+        if use_colors:
+            use_colors = coloredlogs.terminal_supports_colors()
+    if use_colors:
+        formatter = coloredlogs.ColoredFormatter(fmt=fmt)
+    else:
+        formatter = logging.Formatter(fmt=fmt)
+
+    console.setFormatter(formatter)
+    log.addHandler(console)
+
+    if verbosity <= 1:
+        pdfminer_log = logging.getLogger('pdfminer')
+        pdfminer_log.setLevel(logging.ERROR)
+        pil_log = logging.getLogger('PIL')
+        pil_log.setLevel(logging.INFO)
+
+    if manage_root_logger:
+        logging.captureWarnings(True)
+
+    return log
+
+
+def create_options(
+    *, input_file: PathOrIO, output_file: PathOrIO, parser: ArgumentParser, **kwargs
+):
+    cmdline = []
+    deferred = []
+
+    for arg, val in kwargs.items():
+        if val is None:
+            continue
+
+        # These arguments with special handling for which we bypass
+        # argparse
+        if arg in {'progress_bar', 'plugins'}:
+            deferred.append((arg, val))
+            continue
+
+        cmd_style_arg = arg.replace('_', '-')
+
+        # Booleans are special: add only if True, omit for False
+        if isinstance(val, bool):
+            if val:
+                cmdline.append(f"--{cmd_style_arg}")
+            continue
+
+        if is_iterable_notstr(val):
+            for elem in val:
+                cmdline.append(f"--{cmd_style_arg}")
+                cmdline.append(elem)
+            continue
+
+        # We have a parameter
+        cmdline.append(f"--{cmd_style_arg}")
+        if isinstance(val, (int, float)):
+            cmdline.append(str(val))
+        elif isinstance(val, str):
+            cmdline.append(val)
+        elif isinstance(val, Path):
+            cmdline.append(str(val))
+        else:
+            raise TypeError(f"{arg}: {val} ({type(val)})")
+
+    try:
+        cmdline.append(os.fspath(input_file))
+    except TypeError:
+        cmdline.append('stream://input_file')
+    try:
+        cmdline.append(os.fspath(output_file))
+    except TypeError:
+        cmdline.append('stream://output_file')
+
+    parser._api_mode = True
+    options = parser.parse_args(cmdline)
+    for keyword, val in deferred:
+        setattr(options, keyword, val)
+
+    if options.input_file == 'stream://input_file':
+        options.input_file = input_file
+    if options.output_file == 'stream://output_file':
+        options.output_file = output_file
+
+    return options
+
+
+def ocr(  # pylint: disable=unused-argument
+    input_file: PathOrIO,
+    output_file: PathOrIO,
+    *,
+    language: Iterable[str] = None,
+    image_dpi: int = None,
+    output_type=None,
+    sidecar: os.PathLike = None,
+    jobs: int = None,
+    use_threads: bool = None,
+    title: str = None,
+    author: str = None,
+    subject: str = None,
+    keywords: str = None,
+    rotate_pages: bool = None,
+    remove_background: bool = None,
+    deskew: bool = None,
+    clean: bool = None,
+    clean_final: bool = None,
+    unpaper_args: str = None,
+    oversample: int = None,
+    remove_vectors: bool = None,
+    threshold: bool = None,
+    force_ocr: bool = None,
+    skip_text: bool = None,
+    redo_ocr: bool = None,
+    skip_big: float = None,
+    optimize: int = None,
+    jpg_quality: int = None,
+    png_quality: int = None,
+    jbig2_lossy: bool = None,
+    jbig2_page_group_size: int = None,
+    pages: str = None,
+    max_image_mpixels: float = None,
+    tesseract_config: Iterable[str] = None,
+    tesseract_pagesegmode: int = None,
+    tesseract_oem: int = None,
+    pdf_renderer=None,
+    tesseract_timeout: float = None,
+    rotate_pages_threshold: float = None,
+    pdfa_image_compression=None,
+    user_words: os.PathLike = None,
+    user_patterns: os.PathLike = None,
+    fast_web_view: float = None,
+    plugins: Iterable[str] = None,
+    keep_temporary_files: bool = None,
+    progress_bar: bool = None,
+    **kwargs,
+):
+    """Run OCRmyPDF on one PDF or image.
+
+    For most arguments, see documentation for the equivalent command line parameter.
+    A few specific arguments are discussed here:
+
+    Args:
+        use_threads: Use worker threads instead of processes. This reduces
+            performance but may make debugging easier since it is easier to set
+            breakpoints.
+        input_file: If a :class:`pathlib.Path`, ``str`` or ``bytes``, this is
+            interpreted as file system path to the input file. If the object
+            appears to be a readable stream (with methods such as ``.read()``
+            and ``.seek()``), the object will be read in its entirety and saved to
+            a temporary file. If ``input_file`` is  ``"-"``, standard input will be
+            read.
+        output_file: If a :class:`pathlib.Path`, ``str`` or ``bytes``, this is
+            interpreted as file system path to the output file. If the object
+            appears to be a writable stream (with methods such as ``.read()`` and
+            ``.seek()``), the output will be written to this stream. If
+            ``output_file`` is ``"-"``, the output will be written to ``sys.stdout``
+            (provided that standard output does not seem to be a terminal device).
+            When a stream is used as output, whether via a writable object or
+            ``"-"``, some final validation steps are not performed (we do not read
+            back the stream after it is written).
+    Raises:
+        ocrmypdf.PdfMergeFailedError: If the input PDF is malformed, preventing merging
+            with the OCR layer.
+        ocrmypdf.MissingDependencyError: If a required dependency program is missing or
+            was not found on PATH.
+        ocrmypdf.UnsupportedImageFormatError: If the input file type was an image that
+            could not be read, or some other file type that is not a PDF.
+        ocrmypdf.DpiError: If the input file is an image, but the resolution of the
+            image is not credible (allowing it to proceed would cause poor OCR).
+        ocrmypdf.OutputFileAccessError: If an attempt to write to the intended output
+            file failed.
+        ocrmypdf.PriorOcrFoundError: If the input PDF seems to have OCR or digital
+            text already, and settings did not tell us to proceed.
+        ocrmypdf.InputFileError: Any other problem with the input file.
+        ocrmypdf.SubprocessOutputError: Any error related to executing a subprocess.
+        ocrmypdf.EncryptedPdfERror: If the input PDF is encrypted (password protected).
+            OCRmyPDF does not remove passwords.
+        ocrmypdf.TesseractConfigError: If Tesseract reported its configuration was not
+            valid.
+
+    Returns:
+        :class:`ocrmypdf.ExitCode`
+    """
+    if not plugins:
+        plugins = []
+    else:
+        plugins = list(plugins)
+
+    parser = get_parser()
+    _plugin_manager = get_plugin_manager(plugins)
+    _plugin_manager.hook.add_options(parser=parser)  # pylint: disable=no-member
+
+    create_options_kwargs = {
+        k: v for k, v in locals().items() if not k.startswith('_') and k != 'kwargs'
+    }
+    create_options_kwargs.update(kwargs)
+
+    options = create_options(**create_options_kwargs)
+    check_options(options, _plugin_manager)
+    return run_pipeline(options=options, plugin_manager=_plugin_manager, api=True)

src/ocrmypdf/builtin_plugins/__init__.py

@@ -0,0 +1,16 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.

src/ocrmypdf/builtin_plugins/ghostscript.py

@@ -0,0 +1,102 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+
+from ocrmypdf import hookimpl
+from ocrmypdf._exec import ghostscript
+from ocrmypdf._validation import HOCR_OK_LANGS
+from ocrmypdf.exceptions import MissingDependencyError
+from ocrmypdf.subprocess import check_external_program
+
+log = logging.getLogger(__name__)
+
+
+@hookimpl
+def check_options(options):
+    gs_version = ghostscript.version()
+    check_external_program(
+        program='gs',
+        package='ghostscript',
+        version_checker=gs_version,
+        need_version='9.15',  # limited by Travis CI / Ubuntu 14.04 backports
+    )
+    if gs_version in ('9.24', '9.51'):
+        raise MissingDependencyError(
+            f"Ghostscript {gs_version} contains serious regressions and is not "
+            "supported. Please upgrade to a newer version, or downgrade to the "
+            "previous version."
+        )
+
+    # We have these constraints to check for.
+    # 1. Ghostscript < 9.20 mangles multibyte Unicode
+    # 2. hocr doesn't work on non-Latin languages (so don't select it)
+    is_latin = options.languages.issubset(HOCR_OK_LANGS)
+    if gs_version < '9.20' and options.output_type != 'pdf' and not is_latin:
+        # https://bugs.ghostscript.com/show_bug.cgi?id=696874
+        # Ghostscript < 9.20 fails to encode multibyte characters properly
+        msg = (
+            "The installed version of Ghostscript does not work correctly "
+            "with the OCR languages you specified. Use --output-type pdf or "
+            "upgrade to Ghostscript 9.20 or later to avoid this issue."
+        )
+        msg += f"Found Ghostscript {gs_version}"
+        log.warning(msg)
+
+    if options.output_type == 'pdfa':
+        options.output_type = 'pdfa-2'
+
+    if options.output_type == 'pdfa-3' and ghostscript.version() < '9.19':
+        raise MissingDependencyError(
+            "--output-type pdfa-3 requires Ghostscript 9.19 or later"
+        )
+
+
+@hookimpl
+def rasterize_pdf_page(
+    input_file,
+    output_file,
+    raster_device,
+    raster_dpi,
+    pageno,
+    page_dpi=None,
+    rotation=None,
+    filter_vector=False,
+):
+    ghostscript.rasterize_pdf(
+        input_file,
+        output_file,
+        raster_device=raster_device,
+        raster_dpi=raster_dpi,
+        pageno=pageno,
+        page_dpi=page_dpi,
+        rotation=rotation,
+        filter_vector=filter_vector,
+    )
+    return output_file
+
+
+@hookimpl
+def generate_pdfa(pdf_pages, pdfmark, output_file, compression, pdf_version, pdfa_part):
+    ghostscript.generate_pdfa(
+        pdf_pages=[*pdf_pages, pdfmark],
+        output_file=output_file,
+        compression=compression,
+        pdf_version=pdf_version,
+        pdfa_part=pdfa_part,
+    )
+    return output_file

src/ocrmypdf/builtin_plugins/tesseract_ocr.py

@@ -0,0 +1,197 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+import os
+
+from ocrmypdf import hookimpl
+from ocrmypdf._exec import tesseract
+from ocrmypdf.cli import numeric
+from ocrmypdf.exceptions import MissingDependencyError
+from ocrmypdf.helpers import clamp
+from ocrmypdf.pluginspec import OcrEngine
+from ocrmypdf.subprocess import check_external_program
+
+log = logging.getLogger(__name__)
+
+
+@hookimpl
+def add_options(parser):
+    tess = parser.add_argument_group("Tesseract", "Advanced control of Tesseract OCR")
+    tess.add_argument(
+        '--tesseract-config',
+        action='append',
+        metavar='CFG',
+        default=[],
+        help="Additional Tesseract configuration files -- see documentation",
+    )
+    tess.add_argument(
+        '--tesseract-pagesegmode',
+        action='store',
+        type=int,
+        metavar='PSM',
+        choices=range(0, 14),
+        help="Set Tesseract page segmentation mode (see tesseract --help)",
+    )
+    tess.add_argument(
+        '--tesseract-oem',
+        action='store',
+        type=int,
+        metavar='MODE',
+        choices=range(0, 4),
+        help=(
+            "Set Tesseract 4.0 OCR engine mode: "
+            "0 - original Tesseract only; "
+            "1 - neural nets LSTM only; "
+            "2 - Tesseract + LSTM; "
+            "3 - default."
+        ),
+    )
+    tess.add_argument(
+        '--tesseract-timeout',
+        default=180.0,
+        type=numeric(float, 0),
+        metavar='SECONDS',
+        help='Give up on OCR after the timeout, but copy the preprocessed page '
+        'into the final output',
+    )
+    tess.add_argument(
+        '--user-words',
+        metavar='FILE',
+        help="Specify the location of the Tesseract user words file. This is a "
+        "list of words Tesseract should consider while performing OCR in "
+        "addition to its standard language dictionaries. This can improve "
+        "OCR quality especially for specialized and technical documents.",
+    )
+    tess.add_argument(
+        '--user-patterns',
+        metavar='FILE',
+        help="Specify the location of the Tesseract user patterns file.",
+    )
+
+
+@hookimpl
+def check_options(options):
+    check_external_program(
+        program='tesseract',
+        package={'linux': 'tesseract-ocr'},
+        version_checker=tesseract.version,
+        need_version='4.0.0',  # using backport for Travis CI
+    )
+
+    # Decide on what renderer to use
+    if options.pdf_renderer == 'auto':
+        options.pdf_renderer = 'sandwich'
+
+    if options.pdf_renderer == 'sandwich' and not tesseract.has_textonly_pdf(
+        set(options.languages)
+    ):
+        raise MissingDependencyError(
+            "You are using an alpha version of Tesseract 4.0 that does not support "
+            "the textonly_pdf parameter. We don't support versions this old."
+        )
+    if not tesseract.has_user_words() and (options.user_words or options.user_patterns):
+        log.warning(
+            "Tesseract 4.0 ignores --user-words and --user-patterns, so these "
+            "arguments have no effect."
+        )
+    if options.tesseract_pagesegmode in (0, 2):
+        log.warning(
+            "The --tesseract-pagesegmode argument you select will disable OCR. "
+            "This may cause processing to fail."
+        )
+
+
+@hookimpl
+def validate(pdfinfo, options):
+    # Tesseract 4.x can be multithreaded, and we also run multiple workers. We want
+    # to manage how many threads it uses to avoid creating total threads than cores.
+    # Performance testing shows we're better off
+    # parallelizing ocrmypdf and forcing Tesseract to be single threaded, which we
+    # get by setting the envvar OMP_THREAD_LIMIT to 1. But if the page count of the
+    # input file is small, then we allow Tesseract to use threads, subject to the
+    # constraint: (ocrmypdf workers) * (tesseract threads) <= max_workers.
+    # As of Tesseract 4.1, 3 threads is the most effective on a 4 core/8 thread system.
+    if not os.environ.get('OMP_THREAD_LIMIT', '').isnumeric():
+        tess_threads = clamp(options.jobs // len(pdfinfo), 1, 3)
+        os.environ['OMP_THREAD_LIMIT'] = str(tess_threads)
+    else:
+        tess_threads = int(os.environ['OMP_THREAD_LIMIT'])
+
+    if tess_threads > 1:
+        log.info("Using Tesseract OpenMP thread limit %d", tess_threads)
+
+
+class TesseractOcrEngine(OcrEngine):
+    @staticmethod
+    def version():
+        return tesseract.version()
+
+    @staticmethod
+    def creator_tag(options):
+        tag = '-PDF' if options.pdf_renderer == 'sandwich' else ''
+        return f"Tesseract OCR{tag} {TesseractOcrEngine.version()}"
+
+    def __str__(self):
+        return f"Tesseract OCR {TesseractOcrEngine.version()}"
+
+    @staticmethod
+    def languages(options):
+        return tesseract.get_languages()
+
+    @staticmethod
+    def get_orientation(input_file, options):
+        return tesseract.get_orientation(
+            input_file,
+            engine_mode=options.tesseract_oem,
+            timeout=options.tesseract_timeout,
+        )
+
+    @staticmethod
+    def generate_hocr(input_file, output_hocr, output_text, options):
+        tesseract.generate_hocr(
+            input_file=input_file,
+            output_hocr=output_hocr,
+            output_text=output_text,
+            languages=options.languages,
+            engine_mode=options.tesseract_oem,
+            tessconfig=options.tesseract_config,
+            timeout=options.tesseract_timeout,
+            pagesegmode=options.tesseract_pagesegmode,
+            user_words=options.user_words,
+            user_patterns=options.user_patterns,
+        )
+
+    @staticmethod
+    def generate_pdf(input_file, output_pdf, output_text, options):
+        tesseract.generate_pdf(
+            input_file=input_file,
+            output_pdf=output_pdf,
+            output_text=output_text,
+            languages=options.languages,
+            engine_mode=options.tesseract_oem,
+            tessconfig=options.tesseract_config,
+            timeout=options.tesseract_timeout,
+            pagesegmode=options.tesseract_pagesegmode,
+            user_words=options.user_words,
+            user_patterns=options.user_patterns,
+        )
+
+
+@hookimpl
+def get_ocr_engine():
+    return TesseractOcrEngine()

src/ocrmypdf/cli.py

@@ -0,0 +1,492 @@
+# © 2015-19 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import argparse
+
+from ocrmypdf._version import PROGRAM_NAME as _PROGRAM_NAME
+from ocrmypdf._version import __version__ as _VERSION
+
+
+def numeric(basetype, min_=None, max_=None):
+    """Validator for numeric params"""
+    min_ = basetype(min_) if min_ is not None else None
+    max_ = basetype(max_) if max_ is not None else None
+
+    def _numeric(string):
+        value = basetype(string)
+        if (min_ is not None and value < min_) or (max_ is not None and value > max_):
+            msg = "%r not in valid range %r" % (string, (min_, max_))
+            raise argparse.ArgumentTypeError(msg)
+        return value
+
+    _numeric.__name__ = basetype.__name__
+    return _numeric
+
+
+class ArgumentParser(argparse.ArgumentParser):
+    """Override parser's default behavior of calling sys.exit()
+
+    https://stackoverflow.com/questions/5943249/python-argparse-and-controlling-overriding-the-exit-status-code
+    """
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._api_mode = False
+
+    def error(self, message):
+        if not self._api_mode:
+            super().error(message)
+            return
+        raise ValueError(message)
+
+
+class LanguageSetAction(argparse.Action):
+    def __init__(self, option_strings, dest, default=None, **kwargs):
+        if default is None:
+            default = set()
+        super().__init__(option_strings, dest, default=default, **kwargs)
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        dest = getattr(namespace, self.dest)
+        if '+' in values:
+            dest.update(lang for lang in values.split('+'))
+        else:
+            dest.add(values)
+
+
+def get_parser():
+    parser = ArgumentParser(
+        prog=_PROGRAM_NAME,
+        allow_abbrev=True,
+        fromfile_prefix_chars='@',
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        description="""\
+Generates a searchable PDF or PDF/A from a regular PDF.
+
+OCRmyPDF rasterizes each page of the input PDF, optionally corrects page
+rotation and performs image processing, runs the Tesseract OCR engine on the
+image, and then creates a PDF from the OCR information.
+""",
+        epilog="""\
+OCRmyPDF attempts to keep the output file at about the same size.  If a file
+contains losslessly compressed images, and images in the output file will be
+losslessly compressed as well.
+
+PDF is a page description file that attempts to preserve a layout exactly.
+A PDF can contain vector objects (such as text or lines) and raster objects
+(images).  A page might have multiple images.  OCRmyPDF is prepared to deal
+with the wide variety of PDFs that exist in the wild.
+
+When a PDF page contains text, OCRmyPDF assumes that the page has already
+been OCRed or is a "born digital" page that should not be OCRed.  The default
+behavior is to exit in this case without producing a file.  You can use the
+option --skip-text to ignore pages with text, or --force-ocr to rasterize
+all objects on the page and produce an image-only PDF as output.
+
+    ocrmypdf --skip-text file_with_some_text_pages.pdf output.pdf
+
+    ocrmypdf --force-ocr word_document.pdf output.pdf
+
+If you are concerned about long-term archiving of PDFs, use the default option
+--output-type pdfa which converts the PDF to a standardized PDF/A-2b.  This
+removes some features from the PDF such as Javascript or forms. If you want to
+minimize the number of changes made to your PDF, use --output-type pdf.
+
+If OCRmyPDF is given an image file as input, it will attempt to convert the
+image to a PDF before processing.  For more control over the conversion of
+images to PDF, use the Python package img2pdf or other image to PDF software.
+
+For example, this command uses img2pdf to convert all .png files beginning
+with the 'page' prefix to a PDF, fitting each image on A4-sized paper, and
+sending the result to OCRmyPDF through a pipe.
+
+    img2pdf --pagesize A4 page*.png | ocrmypdf - myfile.pdf
+
+Online documentation is located at:
+    https://ocrmypdf.readthedocs.io/en/latest/introduction.html
+
+""",
+    )
+
+    parser.add_argument(
+        'input_file',
+        metavar="input_pdf_or_image",
+        help="PDF file containing the images to be OCRed (or '-' to read from "
+        "standard input)",
+    )
+    parser.add_argument(
+        'output_file',
+        metavar="output_pdf",
+        help="Output searchable PDF file (or '-' to write to standard output). "
+        "Existing files will be ovewritten. If same as input file, the "
+        "input file will be updated only if processing is successful.",
+    )
+    parser.add_argument(
+        '-l',
+        '--language',
+        dest='languages',
+        action=LanguageSetAction,
+        help="Language(s) of the file to be OCRed (see tesseract --list-langs for "
+        "all language packs installed in your system). Use -l eng+deu for "
+        "multiple languages.",
+    )
+    parser.add_argument(
+        '--image-dpi',
+        metavar='DPI',
+        type=int,
+        help="For input image instead of PDF, use this DPI instead of file's.",
+    )
+    parser.add_argument(
+        '--output-type',
+        choices=['pdfa', 'pdf', 'pdfa-1', 'pdfa-2', 'pdfa-3'],
+        default='pdfa',
+        help="Choose output type. 'pdfa' creates a PDF/A-2b compliant file for "
+        "long term archiving (default, recommended) but may not suitable "
+        "for users who want their file altered as little as possible. 'pdfa' "
+        "also has problems with full Unicode text. 'pdf' attempts to "
+        "preserve file contents as much as possible. 'pdf-a1' creates a "
+        "PDF/A1-b file. 'pdf-a2' is equivalent to 'pdfa'. 'pdf-a3' creates a "
+        "PDF/A3-b file.",
+    )
+
+    # Use null string '\0' as sentinel to indicate the user supplied no argument,
+    # since that is the only invalid character for filepaths on all platforms
+    # bool('\0') is True in Python
+    parser.add_argument(
+        '--sidecar',
+        nargs='?',
+        const='\0',
+        default=None,
+        metavar='FILE',
+        help="Generate sidecar text files that contain the same text recognized "
+        "by Tesseract. This may be useful for building a OCR text database. "
+        "If FILE is omitted, the sidecar file be named {output_file}.txt "
+        "If FILE is set to '-', the sidecar is written to stdout (a "
+        "convenient way to preview OCR quality). The output file and sidecar "
+        "may not both use stdout at the same time.",
+    )
+
+    parser.add_argument(
+        '--version',
+        action='version',
+        version=_VERSION,
+        help="Print program version and exit",
+    )
+
+    jobcontrol = parser.add_argument_group("Job control options")
+    jobcontrol.add_argument(
+        '-j',
+        '--jobs',
+        metavar='N',
+        type=numeric(int, 0, 256),
+        help="Use up to N CPU cores simultaneously (default: use all).",
+    )
+    jobcontrol.add_argument(
+        '-q', '--quiet', action='store_true', help="Suppress INFO messages"
+    )
+    jobcontrol.add_argument(
+        '-v',
+        '--verbose',
+        type=numeric(int, 0, 2),
+        default=0,
+        const=1,
+        nargs='?',
+        help="Print more verbose messages for each additional verbose level. Use "
+        "`-v 1` typically for much more detailed logging. Higher numbers "
+        "are probably only useful in debugging.",
+    )
+    jobcontrol.add_argument(
+        '--no-progress-bar',
+        action='store_false',
+        dest='progress_bar',
+        help=argparse.SUPPRESS,
+    )
+    jobcontrol.add_argument(
+        '--use-threads', action='store_true', help=argparse.SUPPRESS
+    )
+
+    metadata = parser.add_argument_group(
+        "Metadata options",
+        "Set output PDF/A metadata (default: copy input document's metadata)",
+    )
+    metadata.add_argument(
+        '--title', type=str, help="Set document title (place multiple words in quotes)"
+    )
+    metadata.add_argument('--author', type=str, help="Set document author")
+    metadata.add_argument(
+        '--subject', type=str, help="Set document subject description"
+    )
+    metadata.add_argument('--keywords', type=str, help="Set document keywords")
+
+    preprocessing = parser.add_argument_group(
+        "Image preprocessing options",
+        "Options to improve the quality of the final PDF and OCR",
+    )
+    preprocessing.add_argument(
+        '-r',
+        '--rotate-pages',
+        action='store_true',
+        help="Automatically rotate pages based on detected text orientation",
+    )
+    preprocessing.add_argument(
+        '--remove-background',
+        action='store_true',
+        help="Attempt to remove background from gray or color pages, setting it "
+        "to white ",
+    )
+    preprocessing.add_argument(
+        '-d',
+        '--deskew',
+        action='store_true',
+        help="Deskew each page before performing OCR",
+    )
+    preprocessing.add_argument(
+        '-c',
+        '--clean',
+        action='store_true',
+        help="Clean pages from scanning artifacts before performing OCR, and send "
+        "the cleaned page to OCR, but do not include the cleaned page in "
+        "the output",
+    )
+    preprocessing.add_argument(
+        '-i',
+        '--clean-final',
+        action='store_true',
+        help="Clean page as above, and incorporate the cleaned image in the final "
+        "PDF.  Might remove desired content.",
+    )
+    preprocessing.add_argument(
+        '--unpaper-args',
+        type=str,
+        default=None,
+        help="A quoted string of arguments to pass to unpaper. Requires --clean. "
+        "Example: --unpaper-args '--layout double'.",
+    )
+    preprocessing.add_argument(
+        '--oversample',
+        metavar='DPI',
+        type=numeric(int, 0, 5000),
+        default=0,
+        help="Oversample images to at least the specified DPI, to improve OCR "
+        "results slightly",
+    )
+    preprocessing.add_argument(
+        '--remove-vectors',
+        action='store_true',
+        help="EXPERIMENTAL. Mask out any vector objects in the PDF so that they "
+        "will not be included in OCR. This can eliminate false characters.",
+    )
+    preprocessing.add_argument(
+        '--threshold',
+        action='store_true',
+        help=(
+            "EXPERIMENTAL. Threshold image to 1bpp before sending it to Tesseract "
+            "for OCR. Can improve OCR quality compared to Tesseract's thresholder."
+        ),
+    )
+
+    ocrsettings = parser.add_argument_group("OCR options", "Control how OCR is applied")
+    ocrsettings.add_argument(
+        '-f',
+        '--force-ocr',
+        action='store_true',
+        help="Rasterize any text or vector objects on each page, apply OCR, and "
+        "save the rastered output (this rewrites the PDF)",
+    )
+    ocrsettings.add_argument(
+        '-s',
+        '--skip-text',
+        action='store_true',
+        help="Skip OCR on any pages that already contain text, but include the "
+        "page in final output; useful for PDFs that contain a mix of "
+        "images, text pages, and/or previously OCRed pages",
+    )
+    ocrsettings.add_argument(
+        '--redo-ocr',
+        action='store_true',
+        help="Attempt to detect and remove the hidden OCR layer from files that "
+        "were previously OCRed with OCRmyPDF or another program. Apply OCR "
+        "to text found in raster images. Existing visible text objects will "
+        "not be changed. If there is no existing OCR, OCR will be added.",
+    )
+    ocrsettings.add_argument(
+        '--skip-big',
+        type=numeric(float, 0, 5000),
+        metavar='MPixels',
+        help="Skip OCR on pages larger than the specified amount of megapixels, "
+        "but include skipped pages in final output",
+    )
+
+    optimizing = parser.add_argument_group(
+        "Optimization options", "Control how the PDF is optimized after OCR"
+    )
+    optimizing.add_argument(
+        '-O',
+        '--optimize',
+        type=int,
+        choices=range(0, 4),
+        default=1,
+        help=(
+            "Control how PDF is optimized after processing:"
+            "0 - do not optimize; "
+            "1 - do safe, lossless optimizations (default); "
+            "2 - do some lossy optimizations; "
+            "3 - do aggressive lossy optimizations (including lossy JBIG2)"
+        ),
+    )
+    optimizing.add_argument(
+        '--jpeg-quality',
+        type=numeric(int, 0, 100),
+        default=0,
+        metavar='Q',
+        help=(
+            "Adjust JPEG quality level for JPEG optimization. "
+            "100 is best quality and largest output size; "
+            "1 is lowest quality and smallest output; "
+            "0 uses the default."
+        ),
+    )
+    optimizing.add_argument(
+        '--jpg-quality',
+        type=numeric(int, 0, 100),
+        default=0,
+        metavar='Q',
+        dest='jpeg_quality',
+        help=argparse.SUPPRESS,  # Alias for --jpeg-quality
+    )
+    optimizing.add_argument(
+        '--png-quality',
+        type=numeric(int, 0, 100),
+        default=0,
+        metavar='Q',
+        help=(
+            "Adjust PNG quality level to use when quantizing PNGs. "
+            "Values have same meaning as with --jpeg-quality"
+        ),
+    )
+    optimizing.add_argument(
+        '--jbig2-lossy',
+        action='store_true',
+        help=(
+            "Enable JBIG2 lossy mode (better compression, not suitable for some "
+            "use cases - see documentation)."
+        ),
+    )
+    optimizing.add_argument(
+        '--jbig2-page-group-size',
+        type=numeric(int, 1, 10000),
+        default=0,
+        metavar='N',
+        # Adjust number of pages to consider at once for JBIG2 compression
+        help=argparse.SUPPRESS,
+    )
+
+    advanced = parser.add_argument_group(
+        "Advanced", "Advanced options to control OCRmyPDF"
+    )
+    advanced.add_argument(
+        '--pages',
+        type=str,
+        help=(
+            "Limit OCR to the specified pages (ranges or comma separated), "
+            "skipping others"
+        ),
+    )
+    advanced.add_argument(
+        '--max-image-mpixels',
+        action='store',
+        type=numeric(float, 0),
+        metavar='MPixels',
+        help="Set maximum number of pixels to unpack before treating an image as a "
+        "decompression bomb",
+        default=128.0,
+    )
+    advanced.add_argument(
+        '--pdf-renderer',
+        choices=['auto', 'hocr', 'sandwich'],
+        default='auto',
+        help="Choose OCR PDF renderer - the default option is to let OCRmyPDF "
+        "choose.  See documentation for discussion.",
+    )
+    advanced.add_argument(
+        '--rotate-pages-threshold',
+        default=14.0,
+        type=numeric(float, 0, 1000),
+        metavar='CONFIDENCE',
+        help="Only rotate pages when confidence is above this value (arbitrary "
+        "units reported by tesseract)",
+    )
+    advanced.add_argument(
+        '--pdfa-image-compression',
+        choices=['auto', 'jpeg', 'lossless'],
+        default='auto',
+        help="Specify how to compress images in the output PDF/A. 'auto' lets "
+        "OCRmyPDF decide.  'jpeg' changes all grayscale and color images to "
+        "JPEG compression.  'lossless' uses PNG-style lossless compression "
+        "for all images.  Monochrome images are always compressed using a "
+        "lossless codec.  Compression settings "
+        "are applied to all pages, including those for which OCR was "
+        "skipped.  Not supported for --output-type=pdf ; that setting "
+        "preserves the original compression of all images.",
+    )
+    advanced.add_argument(
+        '--fast-web-view',
+        type=numeric(float, 0),
+        default=1.0,
+        metavar="MEGABYTES",
+        help="If the size of file is more than this threshold (in MB), then "
+        "linearize the PDF for fast web viewing. This allows the PDF to be "
+        "displayed before it is fully downloaded in web browsers, but increases "
+        "the space required slightly. By default we skip this for small files "
+        "which do not benefit. If the threshold is 0 it will be apply to all files. "
+        "Set the threshold very high to disable.",
+    )
+    advanced.add_argument(
+        '--plugin',
+        dest='plugins',
+        action='append',
+        default=[],
+        help="Name of plugin to import. Argument may be issued multiple times to "
+        "import multiple plugins. Plugins may be specified as module names in "
+        "Python syntax, provided they are installed in the same Python (virtual) "
+        "environment as ocrmypdf; or you may give the path to the Python file that "
+        "contains the plugin. Plugins must conform to the specification in the "
+        "OCRmyPDF documentation.",
+    )
+
+    debugging = parser.add_argument_group(
+        "Debugging", "Arguments to help with troubleshooting and debugging"
+    )
+    debugging.add_argument(
+        '-k',
+        '--keep-temporary-files',
+        action='store_true',
+        help="Keep temporary files (helpful for debugging)",
+    )
+    return parser
+
+
+plugins_only_parser = ArgumentParser(
+    prog=_PROGRAM_NAME, fromfile_prefix_chars='@', add_help=False, allow_abbrev=False
+)
+plugins_only_parser.add_argument(
+    '--plugin',
+    dest='plugins',
+    action='append',
+    default=[],
+    help="Name of plugin to import.",
+)

src/ocrmypdf/exec/__init__.py

@@ -1,173 +0,0 @@
-# © 2016 James R. Barlow: github.com/jbarlow83
-#
-# This file is part of OCRmyPDF.
-#
-# OCRmyPDF is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# OCRmyPDF is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
-
-"""Wrappers to manage subprocess calls"""
-
-import os
-import re
-import sys
-from subprocess import run, STDOUT, PIPE, CalledProcessError
-from ..exceptions import MissingDependencyError, ExitCode
-from collections.abc import Mapping
-
-
-def get_version(program, *, version_arg='--version', regex=r'(\d+(\.\d+)*)'):
-    "Get the version of the specified program"
-    args_prog = [program, version_arg]
-    try:
-        proc = run(
-            args_prog,
-            close_fds=True,
-            universal_newlines=True,
-            stdout=PIPE,
-            stderr=STDOUT,
-            check=True,
-        )
-        output = proc.stdout
-    except FileNotFoundError as e:
-        raise MissingDependencyError(
-            f"Could not find program '{program}' on the PATH"
-        ) from e
-    except CalledProcessError as e:
-        if e.returncode != 0:
-            raise MissingDependencyError(
-                f"Ran program '{program}' but it exited with an error:\n{e.output}"
-            ) from e
-        raise MissingDependencyError(
-            f"Could not find program '{program}' on the PATH"
-        ) from e
-    try:
-        version = re.match(regex, output.strip()).group(1)
-    except AttributeError as e:
-        raise MissingDependencyError(
-            f"The program '{program}' did not report its version. "
-            f"Message was:\n{output}"
-        )
-
-    return version
-
-
-missing_program = '''
-The program '{program}' could not be executed or was not found on your
-system PATH.
-'''
-
-missing_optional_program = '''
-The program '{program}' could not be executed or was not found on your
-system PATH.  This program is required when you use the
-{required_for} arguments.  You could try omitting these arguments, or install
-the package.
-'''
-
-missing_recommend_program = '''
-The program '{program}' could not be executed or was not found on your
-system PATH.  This program is recommended when using the {required_for} arguments,
-but not required, so we will proceed.  For best results, install the program.
-'''
-
-old_version = '''
-OCRmyPDF requires '{program}' {need_version} or higher.  Your system appears
-to have {found_version}.  Please update this program.
-'''
-
-old_version_required_for = '''
-OCRmyPDF requires '{program}' {need_version} or higher when run with the
-{required_for} arguments.  If you omit these arguments, OCRmyPDF may be able to
-proceed.  For best results, install the program.
-'''
-
-osx_install_advice = '''
-If you have homebrew installed, try these command to install the missing
-package:
-    brew install {package}
-'''
-
-linux_install_advice = '''
-On systems with the aptitude package manager (Debian, Ubuntu), try these
-commands:
-    sudo apt-get update
-    sudo apt-get install {package}
-
-On RPM-based systems (Red Hat, Fedora), search for instructions on
-installing the RPM for {program}.
-'''
-
-
-def _get_platform():
-    if sys.platform.startswith('freebsd'):
-        return 'freebsd'
-    elif sys.platform.startswith('linux'):
-        return 'linux'
-    return sys.platform
-
-
-def _error_trailer(log, program, package, **kwargs):
-    if isinstance(package, Mapping):
-        package = package[_get_platform()]
-
-    if _get_platform() == 'darwin':
-        log.info(osx_install_advice.format(**locals()))
-    elif _get_platform() == 'linux':
-        log.info(linux_install_advice.format(**locals()))
-
-
-def _error_missing_program(log, program, package, required_for, recommended):
-    if required_for:
-        log.error(missing_optional_program.format(**locals()))
-    elif recommended:
-        log.info(missing_recommend_program.format(**locals()))
-    else:
-        log.error(missing_program.format(**locals()))
-    _error_trailer(**locals())
-
-
-def _error_old_version(
-    log, program, package, need_version, found_version, required_for
-):
-    if required_for:
-        log.error(old_version_required_for.format(**locals()))
-    else:
-        log.error(old_version.format(**locals()))
-    _error_trailer(**locals())
-
-
-def check_external_program(
-    *,
-    log,
-    program,
-    package,
-    version_checker,
-    need_version,
-    required_for=None,
-    recommended=False,
-):
-    try:
-        found_version = version_checker()
-    except (CalledProcessError, FileNotFoundError, MissingDependencyError):
-        _error_missing_program(log, program, package, required_for, recommended)
-        if not recommended:
-            sys.exit(ExitCode.missing_dependency)
-        return
-
-    if found_version < need_version:
-        _error_old_version(
-            log, program, package, need_version, found_version, required_for
-        )
-        if not recommended:
-            sys.exit(ExitCode.missing_dependency)
-
-    log.debug(f'Found {program} {found_version}')

src/ocrmypdf/exec/ghostscript.py

@@ -1,308 +0,0 @@
-# © 2017 James R. Barlow: github.com/jbarlow83
-#
-# This file is part of OCRmyPDF.
-#
-# OCRmyPDF is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# OCRmyPDF is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
-
-import re
-from functools import lru_cache
-from os import fspath
-from shutil import copy
-from subprocess import PIPE, STDOUT, run
-from tempfile import NamedTemporaryFile
-
-from PIL import Image
-
-from . import get_version
-from ..exceptions import SubprocessOutputError
-
-
-@lru_cache(maxsize=1)
-def version():
-    return get_version('gs')
-
-
-def jpeg_passthrough_available():
-    """Returns True if the installed version of Ghostscript supports JPEG passthru
-
-    Prior to 9.23, Ghostscript decode and re-encoded JPEGs internally. In 9.23
-    it gained the ability to keep JPEGs unmodified. However, the 9.23
-    implementation was buggy and would deletes the last two bytes of images in
-    some cases, as reported here.
-    https://bugs.ghostscript.com/show_bug.cgi?id=699216
-
-    The issue was fixed for 9.24, hence that is the first version we consider
-    the feature available. (However, we don't use 9.24 at all, so the first
-    version that allows JPEG passthrough is 9.25.
-
-    """
-    return version() >= '9.24'
-
-
-def _gs_error_reported(stream):
-    return re.search(r'error', stream, flags=re.IGNORECASE)
-
-
-def extract_text(input_file, pageno=1):
-    """Use the txtwrite device to get text layout information out
-
-    For details on options of -dTextFormat see
-    https://www.ghostscript.com/doc/current/VectorDevices.htm#TXT
-
-    Format is like
-    <page>
-    <line>
-    <span bbox="left top right bottom" font="..." size="...">
-    <char bbox="...." c="X"/>
-
-    :param pageno: number of page to extract, or all pages if None
-    :return: XML-ish text representation in bytes
-    """
-
-    if pageno is not None:
-        pages = ['-dFirstPage=%i' % pageno, '-dLastPage=%i' % pageno]
-    else:
-        pages = []
-
-    args_gs = (
-        [
-            'gs',
-            '-dQUIET',
-            '-dSAFER',
-            '-dBATCH',
-            '-dNOPAUSE',
-            '-sDEVICE=txtwrite',
-            '-dTextFormat=0',
-        ]
-        + pages
-        + ['-o', '-', fspath(input_file)]
-    )
-
-    p = run(args_gs, stdout=PIPE, stderr=PIPE)
-    if p.returncode != 0:
-        raise SubprocessOutputError(
-            'Ghostscript text extraction failed\n%s\n%s\n%s'
-            % (input_file, p.stdout.decode(), p.stderr.decode())
-        )
-
-    return p.stdout
-
-
-def rasterize_pdf(
-    input_file,
-    output_file,
-    xres,
-    yres,
-    raster_device,
-    log,
-    pageno=1,
-    page_dpi=None,
-    rotation=None,
-    filter_vector=False,
-):
-    """Rasterize one page of a PDF at resolution (xres, yres) in canvas units.
-
-    The image is sized to match the integer pixels dimensions implied by
-    (xres, yres) even if those numbers are noninteger. The image's DPI will
-     be overridden with the values in page_dpi.
-
-    :param input_file: pathlike
-    :param output_file: pathlike
-    :param xres: resolution at which to rasterize page
-    :param yres:
-    :param raster_device:
-    :param log:
-    :param pageno: page number to rasterize (beginning at page 1)
-    :param page_dpi: resolution tuple (x, y) overriding output image DPI
-    :param rotation: 0, 90, 180, 270: clockwise angle to rotate page
-    :param filter_vector: if True, remove vector graphics objects
-    :return:
-    """
-    res = xres, yres
-    int_res = round(xres), round(yres)
-    if not page_dpi:
-        page_dpi = res
-
-    with NamedTemporaryFile(delete=True) as tmp:
-        args_gs = (
-            [
-                'gs',
-                '-dQUIET',
-                '-dSAFER',
-                '-dBATCH',
-                '-dNOPAUSE',
-                f'-sDEVICE={raster_device}',
-                f'-dFirstPage={pageno}',
-                f'-dLastPage={pageno}',
-                f'-r{str(int_res[0])}x{str(int_res[1])}',
-            ]
-            + (['-dFILTERVECTOR'] if filter_vector else [])
-            + [
-                '-o',
-                tmp.name,
-                '-dAutoRotatePages=/None',  # Probably has no effect on raster
-                '-f',
-                fspath(input_file),
-            ]
-        )
-
-        log.debug(args_gs)
-        p = run(args_gs, stdout=PIPE, stderr=STDOUT, universal_newlines=True)
-        if _gs_error_reported(p.stdout):
-            log.error(p.stdout)
-        else:
-            log.debug(p.stdout)
-
-        if p.returncode != 0:
-            log.error('Ghostscript rasterizing failed')
-            raise SubprocessOutputError()
-
-        # Ghostscript only accepts integers for output resolution
-        # if the resolution happens to be fractional, then the discrepancy
-        # would change the size of the output page, especially if the DPI
-        # is quite low. Resize the image to the expected size
-
-        tmp.seek(0)
-        with Image.open(tmp) as im:
-            expected_size = (
-                round(im.size[0] / int_res[0] * res[0]),
-                round(im.size[1] / int_res[1] * res[1]),
-            )
-            if expected_size != im.size or page_dpi != (xres, yres):
-                log.debug(
-                    f"Ghostscript: resize output image {im.size} -> {expected_size}"
-                )
-                im = im.resize(expected_size)
-
-            if rotation is not None:
-                log.debug("Rotating output by %i", rotation)
-                # rotation is a clockwise angle and Image.ROTATE_* is
-                # counterclockwise so this cancels out the rotation
-                if rotation == 90:
-                    im = im.transpose(Image.ROTATE_90)
-                elif rotation == 180:
-                    im = im.transpose(Image.ROTATE_180)
-                elif rotation == 270:
-                    im = im.transpose(Image.ROTATE_270)
-                if rotation % 180 == 90:
-                    page_dpi = page_dpi[1], page_dpi[0]
-            im.save(fspath(output_file), dpi=page_dpi)
-
-
-def generate_pdfa(
-    pdf_pages,
-    output_file,
-    compression,
-    log,
-    threads=1,
-    pdf_version='1.5',
-    pdfa_part='2',
-):
-    """Generate a PDF/A.
-
-    The pdf_pages, a list files, will be merged into output_file. One or more
-    PDF files may be merged. One of the files in this list must be a pdfmark
-    file that provides Ghostscript with details on how to perform the PDF/A
-    conversion. By default with we pick PDF/A-2b, but this works for 1 or 3.
-
-    compression can be 'jpeg', 'lossless', or an empty string. In 'jpeg',
-    Ghostscript is instructed to convert color and grayscale images to DCT
-    (JPEG encoding). In 'lossless' Ghostscript is told to convert images to
-    Flate (lossless/PNG). If the parameter is omitted Ghostscript is left to
-    make its own decisions about how to encode images; it appears to use a
-    heuristic to decide how to encode images. As of Ghostscript 9.25, we
-    support passthrough JPEG which allows Ghostscript to avoid transcoding
-    images entirely. (The feature was added in 9.23 but broken, and the 9.24
-    release of Ghostscript had regressions, so we don't support it until 9.25.)
-    """
-    compression_args = []
-    if compression == 'jpeg':
-        compression_args = [
-            "-dAutoFilterColorImages=false",
-            "-dColorImageFilter=/DCTEncode",
-            "-dAutoFilterGrayImages=false",
-            "-dGrayImageFilter=/DCTEncode",
-        ]
-    elif compression == 'lossless':
-        compression_args = [
-            "-dAutoFilterColorImages=false",
-            "-dColorImageFilter=/FlateEncode",
-            "-dAutoFilterGrayImages=false",
-            "-dGrayImageFilter=/FlateEncode",
-        ]
-    else:
-        compression_args = [
-            "-dAutoFilterColorImages=true",
-            "-dAutoFilterGrayImages=true",
-        ]
-
-    # Older versions of Ghostscript expect a leading slash in
-    # sColorConversionStrategy, newer ones should not have it. See Ghostscript
-    # git commit fe1c025d.
-    strategy = 'RGB' if version() >= '9.19' else '/RGB'
-
-    if version() == '9.23':
-        # 9.23: new feature JPEG passthrough is broken in some cases, best to
-        # disable it always
-        # https://bugs.ghostscript.com/show_bug.cgi?id=699216
-        compression_args.append('-dPassThroughJPEGImages=false')
-
-    with NamedTemporaryFile(delete=True) as gs_pdf:
-        # nb no need to specify ProcessColorModel when ColorConversionStrategy
-        # is set; see:
-        # https://bugs.ghostscript.com/show_bug.cgi?id=699392
-        args_gs = (
-            [
-                "gs",
-                "-dQUIET",
-                "-dBATCH",
-                "-dNOPAUSE",
-                "-dCompatibilityLevel=" + str(pdf_version),
-                "-dNumRenderingThreads=" + str(threads),
-                "-sDEVICE=pdfwrite",
-                "-dAutoRotatePages=/None",
-                "-sColorConversionStrategy=" + strategy,
-            ]
-            + compression_args
-            + [
-                "-dJPEGQ=95",
-                "-dPDFA=" + pdfa_part,
-                "-dPDFACompatibilityPolicy=1",
-                "-sOutputFile=" + gs_pdf.name,
-            ]
-        )
-        args_gs.extend(fspath(s) for s in pdf_pages)  # Stringify Path objs
-        log.debug(args_gs)
-        p = run(args_gs, stdout=PIPE, stderr=STDOUT, universal_newlines=True)
-
-        if _gs_error_reported(p.stdout):
-            log.error(p.stdout)
-        elif 'overprint mode not set' in p.stdout:
-            # Unless someone is going to print PDF/A documents on a
-            # magical sRGB printer I can't see the removal of overprinting
-            # being a problem....
-            log.debug(
-                "Ghostscript had to remove PDF 'overprinting' from the "
-                "input file to complete PDF/A conversion. "
-            )
-        else:
-            log.debug(p.stdout)
-
-        if p.returncode == 0:
-            # Ghostscript does not change return code when it fails to create
-            # PDF/A - check PDF/A status elsewhere
-            copy(gs_pdf.name, fspath(output_file))
-        else:
-            log.error('Ghostscript PDF/A rendering failed')
-            raise SubprocessOutputError()

src/ocrmypdf/exec/qpdf.py

@@ -1,49 +0,0 @@
-# © 2017 James R. Barlow: github.com/jbarlow83
-#
-# This file is part of OCRmyPDF.
-#
-# OCRmyPDF is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# OCRmyPDF is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
-
-from functools import lru_cache
-from os import fspath
-from subprocess import PIPE, STDOUT, CalledProcessError, run
-
-from . import get_version
-
-
-@lru_cache(maxsize=1)
-def version():
-    return get_version('qpdf', regex=r'qpdf version (.+)')
-
-
-def check(input_file, log=None):
-    args_qpdf = ['qpdf', '--check', fspath(input_file)]
-
-    if log is None:
-        import logging as log
-
-    try:
-        run(args_qpdf, stderr=STDOUT, stdout=PIPE, universal_newlines=True, check=True)
-    except CalledProcessError as e:
-        if e.returncode == 2:
-            log.error("%s: not a valid PDF, and could not repair it.", input_file)
-            log.error("Details:")
-            log.error(e.output)
-        elif e.returncode == 3:
-            log.info("qpdf --check returned warnings:")
-            log.info(e.output)
-        else:
-            log.warning(e.output)
-        return False
-    return True

src/ocrmypdf/helpers.py

@@ -15,32 +15,71 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
+import logging
 import multiprocessing
 import os
-import sys
+import shutil
 import warnings
+from collections import namedtuple
 from collections.abc import Iterable
 from contextlib import suppress
-from functools import partial, wraps
+from functools import wraps
+from io import StringIO
+from math import isclose
 from pathlib import Path
+from typing import Any, Sequence, TypeVar
+
+import pikepdf
+
+log = logging.getLogger(__name__)
 
 
-def re_symlink(input_file, soft_link_name, log=None):
+class Resolution(namedtuple('Resolution', ('x', 'y'))):
+    """The number of pixels per inch in each 2D direction."""
+
+    __slots__ = ()
+
+    def round(self, ndigits: int):
+        return Resolution(round(self.x, ndigits), round(self.y, ndigits))
+
+    def to_int(self):
+        return Resolution(int(round(self.x)), int(round(self.y)))
+
+    @property
+    def is_square(self) -> bool:
+        return isclose(self.x, self.y, rel_tol=1e-3)
+
+    def take_max(self, vals, yvals=None):
+        if yvals is not None:
+            return Resolution(max(self.x, *vals), max(self.y, *yvals))
+        max_x, max_y = self.x, self.y
+        for x, y in vals:
+            max_x = max(x, max_x)
+            max_y = max(y, max_y)
+        return Resolution(max_x, max_y)
+
+    def flip_axis(self):
+        return Resolution(self.y, self.x)
+
+    def __str__(self):
+        return f"{self.x:f}x{self.y:f}"
+
+    def __repr__(self):
+        return f"Resolution({self.x}x{self.y} dpi)"
+
+
+def safe_symlink(input_file: os.PathLike, soft_link_name: os.PathLike):
     """
     Helper function: relinks soft symbolic link if necessary
     """
     input_file = os.fspath(input_file)
     soft_link_name = os.fspath(soft_link_name)
-    if log is None:
-        prdebug = partial(print, file=sys.stderr)
-    else:
-        prdebug = log.debug
 
     # Guard against soft linking to oneself
     if input_file == soft_link_name:
-        prdebug(
-            "Warning: No symbolic link made. You are using "
-            + "the original data directory as the working directory."
+        log.warning(
+            "No symbolic link made. You are using "
+            "the original data directory as the working directory."
         )
         return
 
@@ -48,86 +87,147 @@ def re_symlink(input_file, soft_link_name, log=None):
     if os.path.lexists(soft_link_name):
         # do not delete or overwrite real (non-soft link) file
         if not os.path.islink(soft_link_name):
-            raise FileExistsError("%s exists and is not a link" % soft_link_name)
+            raise FileExistsError(f"{soft_link_name} exists and is not a link")
         try:
             os.unlink(soft_link_name)
         except OSError:
-            prdebug("Can't unlink %s" % (soft_link_name))
+            log.debug("Can't unlink %s", soft_link_name)
 
     if not os.path.exists(input_file):
-        raise FileNotFoundError("trying to create a broken symlink to %s" % input_file)
+        raise FileNotFoundError(f"trying to create a broken symlink to {input_file}")
 
-    prdebug("os.symlink(%s, %s)" % (input_file, soft_link_name))
+    if os.name == 'nt':
+        # Don't actually use symlinks on Windows due to permission issues
+        shutil.copyfile(input_file, soft_link_name)
+        return
+
+    log.debug("os.symlink(%s, %s)", input_file, soft_link_name)
 
     # Create symbolic link using absolute path
     os.symlink(os.path.abspath(input_file), soft_link_name)
 
 
-def is_iterable_notstr(thing):
+def samefile(f1: os.PathLike, f2: os.PathLike):
+    if os.name == 'nt':
+        return f1 == f2
+    else:
+        return os.path.samefile(f1, f2)
+
+
+def is_iterable_notstr(thing: Any) -> bool:
+    """Is this is an iterable type, other than a string?"""
     return isinstance(thing, Iterable) and not isinstance(thing, str)
 
 
-def page_number(input_file):
+def monotonic(L: Sequence) -> bool:
+    """Does list increase monotonically?"""
+    return all(b > a for a, b in zip(L, L[1:]))
+
+
+def page_number(input_file: os.PathLike) -> int:
     """Get one-based page number implied by filename (000002.pdf -> 2)"""
     return int(os.path.basename(os.fspath(input_file))[0:6])
 
 
-def available_cpu_count():
+def available_cpu_count() -> int:
+    """Returns number of CPUs in the system."""
     try:
         return multiprocessing.cpu_count()
     except NotImplementedError:
         pass
-
-    try:
-        import psutil
-
-        return psutil.cpu_count()
-    except (ImportError, AttributeError):
-        pass
-
     warnings.warn(
         "Could not get CPU count.  Assuming one (1) CPU." "Use -j N to set manually."
     )
     return 1
 
 
-def is_file_writable(test_file):
+def is_file_writable(test_file: os.PathLike) -> bool:
     """Intentionally racy test if target is writable.
 
     We intend to write to the output file if and only if we succeed and
     can replace it atomically. Before doing the OCR work, make sure
     the location is writable.
     """
-    p = Path(test_file)
+    try:
+        p = Path(test_file)
+        if p.is_symlink():
+            p = p.resolve(strict=False)
 
-    if p.is_symlink():
-        p = p.resolve(strict=False)
+        # p.is_file() throws an exception in some cases
+        if p.exists() and p.is_file():
+            return os.access(
+                os.fspath(p),
+                os.W_OK,
+                effective_ids=(os.access in os.supports_effective_ids),
+            )
+        else:
+            try:
+                fp = p.open('wb')
+            except OSError:
+                return False
+            else:
+                fp.close()
+                with suppress(OSError):
+                    p.unlink()
+            return True
+    except (EnvironmentError, RuntimeError) as e:
+        log.debug(e)
+        log.error(str(e))
+        return False
 
-    # p.is_file() throws an exception in some cases
-    if p.exists() and p.is_file():
-        return os.access(
-            os.fspath(p),
-            os.W_OK,
-            effective_ids=(os.access in os.supports_effective_ids),
-        )
+
+def check_pdf(input_file: Path) -> bool:
+    """Check if a PDF complies with the PDF specification.
+
+    Checks for proper formatting and proper linearization.
+    """
+    pdf = None
+    try:
+        pdf = pikepdf.open(input_file)
+    except pikepdf.PdfError as e:
+        log.error(e)
+        return False
     else:
+        messages = pdf.check()
+        for msg in messages:
+            if 'error' in msg.lower():
+                log.error(msg)
+            else:
+                log.warning(msg)
+
+        sio = StringIO()
+        linearize = None
         try:
-            fp = p.open('wb')
-        except OSError:
-            return False
+            pdf.check_linearization(sio)
+        except RuntimeError:
+            pass
         else:
-            fp.close()
-            with suppress(OSError):
-                p.unlink()
-        return True
+            linearize = sio.getvalue()
+            if linearize:
+                log.warning(linearize)
+
+        if not messages and not linearize:
+            return True
+        return False
+    finally:
+        if pdf:
+            pdf.close()
 
 
-def flatten_groups(groups):
-    for obj in groups:
-        if is_iterable_notstr(obj):
-            yield from obj
-        else:
-            yield obj
+T = TypeVar('T')
+
+
+def clamp(n: T, smallest: T, largest: T) -> T:
+    """Clamps the value of n to between smallest and largest."""
+    return max(smallest, min(n, largest))
+
+
+def pikepdf_enable_mmap():
+    try:
+        if pikepdf._qpdf.set_access_default_mmap(True):
+            log.debug("pikepdf mmap enabled")
+    except AttributeError:
+        log.debug("pikepdf mmap not available")
 
 
 def deprecated(func):

src/ocrmypdf/hocrtransform.py

@@ -29,11 +29,16 @@
 # SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 import argparse
+import os
 import re
 from collections import namedtuple
+from itertools import chain
 from math import atan, cos, sin
+from pathlib import Path
+from typing import Optional, Tuple, Union
 from xml.etree import ElementTree
 
+from reportlab.lib.colors import black, cyan, magenta, red
 from reportlab.lib.units import inch
 from reportlab.pdfgen.canvas import Canvas
 
@@ -64,9 +69,9 @@ class HocrTransform:
         {'ff': 'ff', 'ffi': 'f‌f‌i', 'ffl': 'f‌f‌l', 'fi': 'fi', 'fl': 'fl'}
     )
 
-    def __init__(self, hocrFileName, dpi):
+    def __init__(self, hocr_filename: Union[str, Path], dpi: float):
         self.dpi = dpi
-        self.hocr = ElementTree.parse(hocrFileName)
+        self.hocr = ElementTree.parse(os.fspath(hocr_filename))
 
         # if the hOCR file has a namespace, ElementTree requires its use to
         # find elements
@@ -77,7 +82,7 @@ class HocrTransform:
 
         # get dimension in pt (not pixel!!!!) of the OCRed image
         self.width, self.height = None, None
-        for div in self.hocr.findall(".//%sdiv[@class='ocr_page']" % (self.xmlns)):
+        for div in self.hocr.findall(self._child_xpath('div', 'ocr_page')):
             coords = self.element_coordinates(div)
             pt_coords = self.pt_from_pixel(coords)
             self.width = pt_coords.x2 - pt_coords.x1
@@ -88,13 +93,13 @@ class HocrTransform:
         if self.width is None or self.height is None:
             raise HocrTransformError("hocr file is missing page dimensions")
 
-    def __str__(self):
+    def __str__(self):  # pragma: no cover
         """
         Return the textual content of the HTML body
         """
         if self.hocr is None:
             return ''
-        body = self.hocr.find(".//%sbody" % (self.xmlns))
+        body = self.hocr.find(self._child_xpath('body'))
         if body:
             return self._get_element_text(body)
         else:
@@ -107,19 +112,19 @@ class HocrTransform:
         text = ''
         if element.text is not None:
             text += element.text
-        for child in element.getchildren():
+        for child in element:
             text += self._get_element_text(child)
         if element.tail is not None:
             text += element.tail
         return text
 
     @classmethod
-    def element_coordinates(cls, element):
+    def element_coordinates(cls, element) -> Rect:
         """
         Returns a tuple containing the coordinates of the bounding box around
         an element
         """
-        out = (0, 0, 0, 0)
+        out = Rect._make(0 for _ in range(4))
         if 'title' in element.attrib:
             matches = cls.box_pattern.search(element.attrib['title'])
             if matches:
@@ -128,7 +133,7 @@ class HocrTransform:
         return out
 
     @classmethod
-    def baseline(cls, element):
+    def baseline(cls, element) -> Tuple[float, float]:
         """
         Returns a tuple containing the baseline slope and intercept.
         """
@@ -136,32 +141,43 @@ class HocrTransform:
             matches = cls.baseline_pattern.search(element.attrib['title'])
             if matches:
                 return float(matches.group(1)), int(matches.group(2))
-        return (0, 0)
+        return (0.0, 0.0)
 
-    def pt_from_pixel(self, pxl):
+    def pt_from_pixel(self, pxl) -> Rect:
         """
         Returns the quantity in PDF units (pt) given quantity in pixels
         """
         return Rect._make((c / self.dpi * inch) for c in pxl)
 
+    def _child_xpath(self, html_tag, html_class=None):
+        xpath = f".//{self.xmlns}{html_tag}"
+        if html_class:
+            xpath += f"[@class='{html_class}']"
+        return xpath
+
     @classmethod
-    def replace_unsupported_chars(cls, s):
+    def replace_unsupported_chars(cls, s: str) -> str:
         """
         Given an input string, returns the corresponding string that:
-        - is available in the helvetica facetype
-        - does not contain any ligature (to allow easy search in the PDF file)
+        * is available in the Helvetica facetype
+        * does not contain any ligature (to allow easy search in the PDF file)
         """
         return s.translate(cls.ligatures)
 
+    def topdown_position(self, element):
+        pxl_line_coords = self.element_coordinates(element)
+        line_box = self.pt_from_pixel(pxl_line_coords)
+        return -line_box.y2
+
     def to_pdf(
         self,
-        outFileName,
-        imageFileName=None,
-        showBoundingboxes=False,
-        fontname="Helvetica",
-        invisibleText=False,
-        interwordSpaces=False,
-    ):
+        out_filename: Path,
+        image_filename: Optional[Path] = None,
+        show_bounding_boxes: bool = False,
+        fontname: str = "Helvetica",
+        invisible_text: bool = False,
+        interword_spaces: bool = False,
+    ) -> None:
         """
         Creates a PDF file with an image superimposed on top of the text.
         Text is positioned according to the bounding box of the lines in
@@ -169,19 +185,36 @@ class HocrTransform:
         The image need not be identical to the image used to create the hOCR
         file.
         It can have a lower resolution, different color mode, etc.
+
+        Arguments:
+            out_filename: Path of PDF to write.
+            image_filename: Image to use for this file. If omitted, the OCR text
+                is shown.
+            show_bounding_boxes: Show bounding boxes around various text regions,
+                for debugging.
+            fontname: Name of font to use.
+            invisible_text: If True, text is rendered invisible so that is
+                selectable but never drawn. If False, text is visible and may
+                be seen if the image is skipped or deleted in Acrobat.
+            interword_spaces: If True, insert spaces between words rather than
+                drawing each word without spaces. Generally this improves text
+                extraction.
         """
         # create the PDF file
         # page size in points (1/72 in.)
-        pdf = Canvas(outFileName, pagesize=(self.width, self.height), pageCompression=1)
+        pdf = Canvas(
+            os.fspath(out_filename),
+            pagesize=(self.width, self.height),
+            pageCompression=1,
+        )
 
         # draw bounding box for each paragraph
         # light blue for bounding box of paragraph
-        pdf.setStrokeColorRGB(0, 1, 1)
+        pdf.setStrokeColor(cyan)
         # light blue for bounding box of paragraph
-        pdf.setFillColorRGB(0, 1, 1)
+        pdf.setFillColor(cyan)
         pdf.setLineWidth(0)  # no line for bounding box
-        for elem in self.hocr.findall(".//%sp[@class='%s']" % (self.xmlns, "ocr_par")):
-
+        for elem in self.hocr.iterfind(self._child_xpath('p', 'ocr_par')):
             elemtxt = self._get_element_text(elem).rstrip()
             if len(elemtxt) == 0:
                 continue
@@ -190,14 +223,19 @@ class HocrTransform:
             pt = self.pt_from_pixel(pxl_coords)
 
             # draw the bbox border
-            if showBoundingboxes:
+            if show_bounding_boxes:  # pragma: no cover
                 pdf.rect(
                     pt.x1, self.height - pt.y2, pt.x2 - pt.x1, pt.y2 - pt.y1, fill=1
                 )
 
         found_lines = False
-        for line in self.hocr.findall(
-            ".//%sspan[@class='%s']" % (self.xmlns, "ocr_line")
+        for line in sorted(
+            chain(
+                self.hocr.iterfind(self._child_xpath('span', 'ocr_header')),
+                self.hocr.iterfind(self._child_xpath('span', 'ocr_line')),
+                self.hocr.iterfind(self._child_xpath('span', 'ocr_textfloat')),
+            ),
+            key=self.topdown_position,
         ):
             found_lines = True
             self._do_line(
@@ -205,44 +243,46 @@ class HocrTransform:
                 line,
                 "ocrx_word",
                 fontname,
-                invisibleText,
-                interwordSpaces,
-                showBoundingboxes,
+                invisible_text,
+                interword_spaces,
+                show_bounding_boxes,
             )
 
         if not found_lines:
             # Tesseract did not report any lines (just words)
-            root = self.hocr.find(".//%sdiv[@class='%s']" % (self.xmlns, "ocr_page"))
+            root = self.hocr.find(self._child_xpath('div', 'ocr_page'))
             self._do_line(
                 pdf,
                 root,
                 "ocrx_word",
                 fontname,
-                invisibleText,
-                interwordSpaces,
-                showBoundingboxes,
+                invisible_text,
+                interword_spaces,
+                show_bounding_boxes,
             )
         # put the image on the page, scaled to fill the page
-        if imageFileName is not None:
-            pdf.drawImage(imageFileName, 0, 0, width=self.width, height=self.height)
+        if image_filename is not None:
+            pdf.drawImage(
+                os.fspath(image_filename), 0, 0, width=self.width, height=self.height
+            )
 
         # finish up the page and save it
         pdf.showPage()
         pdf.save()
 
     @classmethod
-    def polyval(cls, poly, x):
+    def polyval(cls, poly, x):  # pragma: no cover
         return x * poly[0] + poly[1]
 
     def _do_line(
         self,
-        pdf,
+        pdf: Canvas,
         line,
-        elemclass,
-        fontname,
-        invisibleText,
-        interwordSpaces,
-        showBoundingboxes,
+        elemclass: str,
+        fontname: str,
+        invisible_text: bool,
+        interword_spaces: bool,
+        show_bounding_boxes: bool,
     ):
         pxl_line_coords = self.element_coordinates(line)
         line_box = self.pt_from_pixel(pxl_line_coords)
@@ -262,17 +302,17 @@ class HocrTransform:
         # on a sloped baseline and the edge of the bounding box.
         fontsize = (line_height - abs(intercept)) / cos_a
         text.setFont(fontname, fontsize)
-        if invisibleText:
+        if invisible_text:
             text.setTextRenderMode(3)  # Invisible (indicates OCR text)
 
         # Intercept is normally negative, so this places it above the bottom
         # of the line box
         baseline_y2 = self.height - (line_box.y2 + intercept)
 
-        if showBoundingboxes:
+        if show_bounding_boxes:  # pragma: no cover
             # draw the baseline in magenta, dashed
             pdf.setDash()
-            pdf.setStrokeColorRGB(0.95, 0.65, 0.95)
+            pdf.setStrokeColor(magenta)
             pdf.setLineWidth(0.5)
             # negate slope because it is defined as a rise/run in pixel
             # coordinates and page coordinates have the y axis flipped
@@ -284,12 +324,12 @@ class HocrTransform:
             )
             # light green for bounding box of word/line
             pdf.setDash(6, 3)
-            pdf.setStrokeColorRGB(1, 0, 0)
+            pdf.setStrokeColor(red)
 
         text.setTextTransform(cos_a, -sin_a, sin_a, cos_a, line_box.x1, baseline_y2)
-        pdf.setFillColorRGB(0, 0, 0)  # text in black
+        pdf.setFillColor(black)  # text in black
 
-        elements = line.findall(".//%sspan[@class='%s']" % (self.xmlns, elemclass))
+        elements = line.findall(self._child_xpath('span', elemclass))
         for elem in elements:
             elemtxt = self._get_element_text(elem).strip()
             elemtxt = self.replace_unsupported_chars(elemtxt)
@@ -298,7 +338,7 @@ class HocrTransform:
 
             pxl_coords = self.element_coordinates(elem)
             box = self.pt_from_pixel(pxl_coords)
-            if interwordSpaces:
+            if interword_spaces:
                 # if  `--interword-spaces` is true, append a space
                 # to the end of each text element to allow simpler PDF viewers
                 # such as PDF.js to better recognize words in search and copy
@@ -318,7 +358,7 @@ class HocrTransform:
             font_width = pdf.stringWidth(elemtxt, fontname, fontsize)
 
             # draw the bbox border
-            if showBoundingboxes:
+            if show_bounding_boxes:  # pragma: no cover
                 pdf.rect(
                     box.x1, self.height - line_box.y2, box_width, line_height, fill=0
                 )
@@ -385,5 +425,5 @@ if __name__ == "__main__":
         args.outputfile,
         args.image,
         args.boundingboxes,
-        interwordSpaces=args.interword_spaces,
+        interword_spaces=args.interword_spaces,
     )

src/ocrmypdf/leptonica.py

@@ -24,31 +24,60 @@ import argparse
 import logging
 import os
 import sys
+import threading
 import warnings
+from collections import deque
 from collections.abc import Sequence
 from contextlib import suppress
 from ctypes.util import find_library
 from functools import lru_cache
-from io import BytesIO
+from io import BytesIO, UnsupportedOperation
 from os import fspath
 from tempfile import TemporaryFile
 
-from .lib._leptonica import ffi
+from ocrmypdf.exceptions import MissingDependencyError
+from ocrmypdf.lib._leptonica import ffi
+from ocrmypdf.subprocess import shim_paths_with_program_files
 
 # pylint: disable=protected-access
 
 logger = logging.getLogger(__name__)
 
-lept = ffi.dlopen(find_library('lept'))
-lept.setMsgSeverity(lept.L_SEVERITY_WARNING)
+if os.name == 'nt':
+    libname = 'liblept-5'
+    os.environ['PATH'] = shim_paths_with_program_files()
+else:
+    libname = 'lept'
+_libpath = find_library(libname)
+if not _libpath:
+    raise MissingDependencyError(
+        """
+        ---------------------------------------------------------------------
+        This error normally occurs when ocrmypdf can't find the Leptonica
+        library, which is usually installed with Tesseract OCR. It could be that
+        Tesseract is not installed properly, we can't find the installation
+        on your system PATH environment variable.
+
+        The library we are looking for is usually called:
+            liblept-5.dll   (Windows)
+            liblept*.dylib  (macOS)
+            liblept*.so     (Linux/BSD)
+
+        Please review our installation procedures to find a solution:
+            https://ocrmypdf.readthedocs.io/en/latest/installation.html
+        ---------------------------------------------------------------------
+        """
+    )
+try:
+    lept = ffi.dlopen(_libpath)
+    lept.setMsgSeverity(lept.L_SEVERITY_WARNING)
+except ffi.error as e:
+    raise MissingDependencyError(
+        f"Leptonica library found at {_libpath}, but we could not access it"
+    ) from e
 
 
-def stderr(*objs):
-    """Shorthand print to stderr."""
-    print("leptonica.py:", *objs, file=sys.stderr)
-
-
-class _LeptonicaErrorTrap:
+class _LeptonicaErrorTrap_Redirect:
     """
     Context manager to trap errors reported by Leptonica.
 
@@ -63,43 +92,57 @@ class _LeptonicaErrorTrap:
 
     """
 
+    leptonica_lock = threading.Lock()
+
     def __init__(self):
         self.tmpfile = None
         self.copy_of_stderr = -1
+        self.no_stderr = False
 
     def __enter__(self):
-        from io import UnsupportedOperation
-
         self.tmpfile = TemporaryFile()
 
         # Save the old stderr, and redirect stderr to temporary file
-        sys.stderr.flush()
+        self.leptonica_lock.acquire()
         try:
+            with suppress(AttributeError):
+                sys.stderr.flush()
             self.copy_of_stderr = os.dup(sys.stderr.fileno())
             os.dup2(self.tmpfile.fileno(), sys.stderr.fileno(), inheritable=False)
+        except AttributeError:
+            # We are in some unusual context where our Python process does not
+            # have a sys.stderr. Leptonica still expects to write to file
+            # descriptor 2, so we are going to ensure it is redirected.
+            self.copy_of_stderr = None
+            self.no_stderr = True
+            os.dup2(self.tmpfile.fileno(), 2, inheritable=False)
         except UnsupportedOperation:
             self.copy_of_stderr = None
-        return
+        except Exception:
+            self.leptonica_lock.release()
+            raise
+        return self
 
     def __exit__(self, exc_type, exc_value, traceback):
         # Restore old stderr
-        sys.stderr.flush()
+        with suppress(AttributeError):
+            sys.stderr.flush()
+
         if self.copy_of_stderr is not None:
             os.dup2(self.copy_of_stderr, sys.stderr.fileno())
             os.close(self.copy_of_stderr)
+        if self.no_stderr:
+            os.close(2)
 
-        # Get data from tmpfile (in with block to ensure it is closed)
-        with self.tmpfile as tmpfile:
-            tmpfile.seek(0)  # Cursor will be at end, so move back to beginning
-            leptonica_output = tmpfile.read().decode(errors='replace')
+        # Get data from tmpfile
+        self.tmpfile.seek(0)  # Cursor will be at end, so move back to beginning
+        leptonica_output = self.tmpfile.read().decode(errors='replace')
+        self.tmpfile.close()
+        self.leptonica_lock.release()
 
-        assert self.tmpfile.closed
-        assert not sys.stderr.closed
-
-        # If there are Python errors, let them bubble up
+        # If there are Python errors, record them
         if exc_type:
             logger.warning(leptonica_output)
-            return False
 
         # If there are Leptonica errors, wrap them in Python excpetions
         if 'Error' in leptonica_output:
@@ -114,6 +157,62 @@ class _LeptonicaErrorTrap:
         return False
 
 
+tls = threading.local()
+tls.trap = None
+
+
+@ffi.callback("void(char *)")
+def _stderr_handler(cstr):
+    msg = ffi.string(cstr).decode(errors='replace')
+    if msg.startswith("Error"):
+        logger.error(msg)
+    elif msg.startswith("Warning"):
+        logger.warning(msg)
+    else:
+        logger.debug(msg)
+    if tls.trap is not None:
+        tls.trap.append(msg)
+    return
+
+
+class _LeptonicaErrorTrap_Queue:
+    def __init__(self):
+        self.queue = deque()
+
+    def __enter__(self):
+        self.queue.clear()
+        tls.trap = self.queue
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        tls.trap = None
+        output = ''.join(self.queue)
+        self.queue.clear()
+
+        # If there are Python errors, record them
+        if exc_type:
+            logger.warning(output)
+
+        if 'Error' in output:
+            if 'image file not found' in output:
+                raise FileNotFoundError()
+            if 'pixWrite: stream not opened' in output:
+                raise LeptonicaIOError()
+            if 'index not valid' in output:
+                raise IndexError()
+            raise LeptonicaError(output)
+        return False
+
+
+try:
+    lept.leptSetStderrHandler(_stderr_handler)
+except ffi.error:
+    # Pre-1.79 Leptonica does not have leptSetStderrHandler
+    _LeptonicaErrorTrap = _LeptonicaErrorTrap_Redirect
+else:
+    # 1.79 have this new symbol
+    _LeptonicaErrorTrap = _LeptonicaErrorTrap_Queue
+
+
 class LeptonicaError(Exception):
     pass
 
@@ -289,9 +388,11 @@ class Pix(LeptonicaObject):
         Leptonica can load TIFF, PNM (PBM, PGM, PPM), PNG, and JPEG.  If
         loading fails then the object will wrap a C null pointer.
         """
-        filename = fspath(path)
-        with _LeptonicaErrorTrap():
-            return cls(lept.pixRead(os.fsencode(filename)))
+        with open(path, 'rb') as py_file:
+            data = py_file.read()
+            buffer = ffi.from_buffer(data)
+            with _LeptonicaErrorTrap():
+                return cls(lept.pixReadMem(buffer, len(buffer)))
 
     def write_implied_format(self, path, jpeg_quality=0, jpeg_progressive=0):
         """Write pix to the filename, with the extension indicating format.
@@ -299,14 +400,22 @@ class Pix(LeptonicaObject):
         jpeg_quality -- quality (iff JPEG; 1 - 100, 0 for default)
         jpeg_progressive -- (iff JPEG; 0 for baseline seq., 1 for progressive)
         """
-        filename = fspath(path)
-        with _LeptonicaErrorTrap():
-            lept.pixWriteImpliedFormat(
-                os.fsencode(filename), self._cdata, jpeg_quality, jpeg_progressive
-            )
+        lept_format = lept.getImpliedFileFormat(os.fsencode(path))
+        with open(path, 'wb') as py_file:
+            data = ffi.new('l_uint8 **pdata')
+            size = ffi.new('size_t *psize')
+            with _LeptonicaErrorTrap():
+                if lept_format == lept.L_JPEG_ENCODE:
+                    lept.pixWriteMemJpeg(
+                        data, size, self._cdata, jpeg_quality, jpeg_progressive
+                    )
+                else:
+                    lept.pixWriteMem(data, size, self._cdata, lept_format)
+            buffer = ffi.buffer(data[0], size[0])
+            py_file.write(buffer)
 
     @classmethod
-    def frompil(self, pillow_image):
+    def frompil(cls, pillow_image):
         """Create a copy of a PIL.Image from this Pix"""
         bio = BytesIO()
         pillow_image.save(bio, format='png', compress_level=1)
@@ -318,7 +427,7 @@ class Pix(LeptonicaObject):
 
     def topil(self):
         """Returns a PIL.Image version of this Pix"""
-        from PIL import Image
+        from PIL import Image  # pylint: disable=import-outside-toplevel
 
         # Leptonica manages data in words, so it implicitly does an endian
         # swap.  Tell Pillow about this when it reads the data.
@@ -489,27 +598,15 @@ class Pix(LeptonicaObject):
             )
             return Pix(thresh_pix)
 
-    def crop_to_foreground(
-        self,
-        threshold=128,
-        mindist=70,
-        erasedist=30,
-        pagenum=0,
-        showmorph=0,
-        display=0,
-        pdfdir=ffi.NULL,
-    ):
+    def crop_to_foreground(self, threshold=128, mindist=70, erasedist=30, showmorph=0):
+        if get_leptonica_version() < 'leptonica-1.76':
+            # Leptonica 1.76 changed the API for pixFindPageForeground; we don't
+            # support the old version
+            raise LeptonicaError("Not available in this version of Leptonica")
         with _LeptonicaErrorTrap():
             cropbox = Box(
                 lept.pixFindPageForeground(
-                    self._cdata,
-                    threshold,
-                    mindist,
-                    erasedist,
-                    pagenum,
-                    showmorph,
-                    display,
-                    pdfdir,
+                    self._cdata, threshold, mindist, erasedist, showmorph, ffi.NULL
                 )
             )
 
@@ -614,9 +711,10 @@ class Pix(LeptonicaObject):
         except (LeptonicaError, ValueError, IndexError):
             return
         finally:
-            with suppress(FileNotFoundError):
-                os.unlink('junkpixt.png')  # leptonica may produce this
-                os.unlink('junkpixt')
+            leptonica_junk = ('junkpixt.png', 'junkpixt')
+            for junk in leptonica_junk:
+                with suppress(FileNotFoundError):
+                    os.unlink(junk)  # leptonica may produce this
 
         for n, s in enumerate(sarray):
             decoded = s.decode()
@@ -823,6 +921,8 @@ def get_leptonica_version():
     Caveat: Leptonica expects the caller to free this memory.  We don't,
     since that would involve binding to libc to access libc.free(),
     a pointless effort to reclaim 100 bytes of memory.
+
+    Reminder that this returns "leptonica-1.xx" or "leptonica-1.yy.0".
     """
     return ffi.string(lept.getLeptonicaVersion()).decode()
 

src/ocrmypdf/lib/compile_leptonica.py

@@ -16,6 +16,8 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
+from pathlib import Path
+
 from cffi import FFI
 
 ffibuilder = FFI()
@@ -74,6 +76,17 @@ struct Pixa
 };
 typedef struct Pixa PIXA;
 
+/*! Array of compressed pix */
+struct PixaComp
+{
+    l_int32              n;         /*!< number of PixComp in ptr array    */
+    l_int32              nalloc;    /*!< number of PixComp ptrs allocated  */
+    l_int32              offset;    /*!< indexing offset into ptr array    */
+    struct PixComp     **pixc;      /*!< the array of ptrs to PixComp      */
+    struct Boxa         *boxa;      /*!< array of boxes                    */
+};
+typedef struct PixaComp PIXAC;
+
 struct Box
 {
     l_int32            x;
@@ -210,9 +223,15 @@ ffibuilder.cdef(
     """
 PIX * pixRead ( const char *filename );
 PIX * pixReadMem ( const l_uint8 *data, size_t size );
+PIX * pixReadStream ( FILE *fp, l_int32 hint );
 PIX * pixScale ( PIX *pixs, l_float32 scalex, l_float32 scaley );
 l_int32 pixFindSkew ( PIX *pixs, l_float32 *pangle, l_float32 *pconf );
 l_int32 pixWriteImpliedFormat ( const char *filename, PIX *pix, l_int32 quality, l_int32 progressive );
+l_int32 getImpliedFileFormat ( const char *filename );
+l_ok pixWriteStream ( FILE *fp, PIX *pix, l_int32 format );
+l_ok pixWriteStreamJpeg ( FILE *fp, PIX *pixs, l_int32 quality, l_int32 progressive );
+l_ok pixWriteMem ( l_uint8 **pdata, size_t *psize, PIX *pix, l_int32 format );
+l_ok pixWriteMemJpeg ( l_uint8 **pdata, size_t *psize, PIX *pix, l_int32 quality, l_int32 progressive );
 l_int32
 pixWriteMemPng(l_uint8  **pdata,
                size_t    *psize,
@@ -294,14 +313,12 @@ pixCleanBackgroundToWhite(PIX       *pixs,
                           l_int32    whiteval);
 
 BOX *
-pixFindPageForeground(PIX         *pixs,
-                      l_int32      threshold,
-                      l_int32      mindist,
-                      l_int32      erasedist,
-                      l_int32      pagenum,
-                      l_int32      showmorph,
-                      l_int32      display,
-                      const char  *pdfdir);
+pixFindPageForeground ( PIX *pixs,
+                        l_int32 threshold,
+                        l_int32 mindist,
+                        l_int32 erasedist,
+                        l_int32 showmorph,
+                        PIXAC *pixac );
 
 PIX *
 pixClipRectangle(PIX   *pixs,
@@ -414,7 +431,10 @@ pixExtractBarcodes(PIX     *pixs,
                    l_int32 debugflag);
 
 BOXA *
-pixLocateBarcodes ( PIX *pixs, l_int32 thresh, PIX **ppixb, PIX **ppixm );
+pixLocateBarcodes ( PIX *pixs,
+ l_int32 thresh,
+ PIX **ppixb,
+ PIX **ppixm );
 
 SARRAY *
 pixReadBarcodes(PIXA     *pixa,
@@ -423,6 +443,12 @@ pixReadBarcodes(PIXA     *pixa,
                 SARRAY  **psaw,
                 l_int32 debugflag);
 
+PIX *
+pixGenHalftoneMask(PIX      *pixs,
+                        PIX     **ppixtext,
+                        l_int32  *phtfound,
+                        PIXA     *pixadb);
+
 l_int32
 l_generateCIDataForPdf(const char *fname,
                        PIX *pix,
@@ -483,6 +509,8 @@ void selDestroy ( SEL **psel );
 l_int32
 setMsgSeverity(l_int32 newsev);
 
+void
+leptSetStderrHandler(void (*handler)(const char *));
 """
 )
 
@@ -491,3 +519,8 @@ ffibuilder.set_source("ocrmypdf.lib._leptonica", None)
 
 if __name__ == '__main__':
     ffibuilder.compile(verbose=True)
+    if Path('ocrmypdf/lib/_leptonica.py').exists() and Path('src/ocrmypdf').exists():
+        output = Path('ocrmypdf/lib/_leptonica.py')
+        output.rename('src/ocrmypdf/lib/_leptonica.py')
+        Path('ocrmypdf/lib').rmdir()
+        Path('ocrmypdf').rmdir()

src/ocrmypdf/optimize.py

@@ -15,51 +15,80 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
-import concurrent.futures
 import logging
 import sys
+import tempfile
 from collections import defaultdict
+from functools import partial
 from os import fspath
 from pathlib import Path
-
-from PIL import Image
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterator,
+    List,
+    MutableSet,
+    NamedTuple,
+    NewType,
+    Optional,
+    Sequence,
+    Tuple,
+    Union,
+)
 
 import pikepdf
-from pikepdf import Name, Dictionary, Array
+from pikepdf import Dictionary, Name, Object, Pdf, PdfImage
+from PIL import Image
+from tqdm import tqdm
 
-from . import leptonica
-from ._jobcontext import JobContext
-from .exec import jbig2enc, pngquant
-from .helpers import re_symlink
+from ocrmypdf import leptonica
+from ocrmypdf._concurrent import exec_progress_pool
+from ocrmypdf._exec import jbig2enc, pngquant
+from ocrmypdf._jobcontext import PdfContext
+from ocrmypdf.exceptions import OutputFileAccessError
+from ocrmypdf.helpers import safe_symlink
+
+log = logging.getLogger(__name__)
 
 DEFAULT_JPEG_QUALITY = 75
 DEFAULT_PNG_QUALITY = 70
 
 
-def img_name(root, xref, ext):
-    return fspath(root / f'{xref:08d}{ext}')
+Xref = NewType('Xref', int)
 
 
-def png_name(root, xref):
+class XrefExt(NamedTuple):
+    xref: Xref
+    ext: str
+
+
+def img_name(root: Path, xref: Xref, ext: str) -> Path:
+    return root / f'{xref:08d}{ext}'
+
+
+def png_name(root: Path, xref: Xref) -> Path:
     return img_name(root, xref, '.png')
 
 
-def jpg_name(root, xref):
+def jpg_name(root: Path, xref: Xref) -> Path:
     return img_name(root, xref, '.jpg')
 
 
-def tif_name(root, xref):
+def tif_name(root: Path, xref: Xref) -> Path:
     return img_name(root, xref, '.tif')
 
 
-def extract_image_filter(pike, root, log, image, xref):
+def extract_image_filter(
+    pike: Pdf, root: Path, image: Object, xref: Xref
+) -> Optional[Tuple[PdfImage, Tuple[Name, Object]]]:
     if image.Subtype != Name.Image:
         return None
     if image.Length < 100:
         log.debug("Skipping small image, xref %s", xref)
         return None
 
-    pim = pikepdf.PdfImage(image)
+    pim = PdfImage(image)
 
     if len(pim.filter_decodeparms) > 1:
         log.debug("Skipping multiply filtered, xref %s", xref)
@@ -72,37 +101,53 @@ def extract_image_filter(pike, root, log, image, xref):
     if filtdp[0] == Name.JPXDecode:
         return None  # Don't do JPEG2000
 
+    if Name.Decode in image:
+        return None  # Don't mess with custom Decode tables
+
     return pim, filtdp
 
 
-def extract_image_jbig2(*, pike, root, log, image, xref, options):
-    result = extract_image_filter(pike, root, log, image, xref)
+def extract_image_jbig2(
+    *, pike: pikepdf.Pdf, root: Path, image: Object, xref: Xref, options
+) -> Optional[XrefExt]:
+    result = extract_image_filter(pike, root, image, xref)
     if result is None:
         return None
     pim, filtdp = result
 
     if (
         pim.bits_per_component == 1
-        and filtdp != Name.JBIG2Decode
+        and filtdp[0] != Name.JBIG2Decode
         and jbig2enc.available()
     ):
         try:
-            imgname = Path(root / f'{xref:08d}')
+            imgname = root / f'{xref:08d}'
             with imgname.open('wb') as f:
                 ext = pim.extract_to(stream=f)
             imgname.rename(imgname.with_suffix(ext))
         except pikepdf.UnsupportedImageTypeError:
             return None
-        return xref, ext
+        return XrefExt(xref, ext)
     return None
 
 
-def extract_image_generic(*, pike, root, log, image, xref, options):
-    result = extract_image_filter(pike, root, log, image, xref)
+def extract_image_generic(
+    *, pike: Pdf, root: Path, image: PdfImage, xref: Xref, options
+) -> Optional[XrefExt]:
+    result = extract_image_filter(pike, root, image, xref)
     if result is None:
         return None
     pim, filtdp = result
 
+    # Don't try to PNG-optimize 1bpp images, since JBIG2 does it better.
+    if pim.bits_per_component == 1:
+        return None
+
+    try:
+        pim.indexed  # pikepdf 1.6.3 can't handle [/Indexed [/Array...]]
+    except NotImplementedError:
+        return None
+
     if filtdp[0] == Name.DCTDecode and options.optimize >= 2:
         # This is a simple heuristic derived from some training data, that has
         # about a 70% chance of guessing whether the JPEG is high quality,
@@ -121,13 +166,13 @@ def extract_image_generic(*, pike, root, log, image, xref, options):
         #     with Image.open(stream) as im:
         #         im.save(jpg_name(root, xref), icc_profile=iccbytes)
         try:
-            imgname = Path(root / f'{xref:08d}')
+            imgname = root / f'{xref:08d}'
             with imgname.open('wb') as f:
                 ext = pim.extract_to(stream=f)
             imgname.rename(imgname.with_suffix(ext))
         except pikepdf.UnsupportedImageTypeError:
             return None
-        return xref, ext
+        return XrefExt(xref, ext)
     elif (
         pim.indexed
         and pim.colorspace in pim.SIMPLE_COLORSPACES
@@ -136,17 +181,30 @@ def extract_image_generic(*, pike, root, log, image, xref, options):
         # Try to improve on indexed images - these are far from low hanging
         # fruit in most cases
         pim.as_pil_image().save(png_name(root, xref))
-        return xref, '.png'
+        return XrefExt(xref, '.png')
     elif not pim.indexed and pim.colorspace in pim.SIMPLE_COLORSPACES:
         # An optimization opportunity here, not currently taken, is directly
         # generating a PNG from compressed data
         pim.as_pil_image().save(png_name(root, xref))
-        return xref, '.png'
+        return XrefExt(xref, '.png')
+    elif (
+        not pim.indexed
+        and pim.colorspace == Name.ICCBased
+        and pim.bits_per_component == 1
+        and not options.jbig2_lossy
+    ):
+        # We can losslessly optimize 1-bit images to CCITT or JBIG2 without
+        # paying any attention to the ICC profile, provided we're not doing
+        # lossy JBIG2
+        pim.as_pil_image().save(png_name(root, xref))
+        return XrefExt(xref, '.png')
 
     return None
 
 
-def extract_images(pike, root, log, options, extract_fn):
+def extract_images(
+    pike: Pdf, root: Path, options, extract_fn: Callable[..., Optional[XrefExt]],
+) -> Iterator[Tuple[int, XrefExt]]:
     """Extract image using extract_fn
 
     Enumerate images on each page, lookup their xref/ID number in the PDF.
@@ -162,8 +220,8 @@ def extract_images(pike, root, log, options, extract_fn):
     extension. extract_fn must also extract the file it finds interesting.
     """
 
-    include_xrefs = set()
-    exclude_xrefs = set()
+    include_xrefs: MutableSet[Xref] = set()
+    exclude_xrefs: MutableSet[Xref] = set()
     pageno_for_xref = {}
     errors = 0
     for pageno, page in enumerate(pike.pages):
@@ -174,10 +232,10 @@ def extract_images(pike, root, log, options, extract_fn):
         for _imname, image in dict(xobjs).items():
             if image.objgen[1] != 0:
                 continue  # Ignore images in an incremental PDF
-            xref = image.objgen[0]
+            xref = Xref(image.objgen[0])
             if hasattr(image, 'SMask'):
                 # Ignore soft masks
-                smask_xref = image.SMask.objgen[0]
+                smask_xref = Xref(image.SMask.objgen[0])
                 exclude_xrefs.add(smask_xref)
             include_xrefs.add(xref)
             if xref not in pageno_for_xref:
@@ -188,41 +246,41 @@ def extract_images(pike, root, log, options, extract_fn):
         image = pike.get_object((xref, 0))
         try:
             result = extract_fn(
-                pike=pike, root=root, log=log, image=image, xref=xref, options=options
+                pike=pike, root=root, image=image, xref=xref, options=options
             )
-        except Exception as e:
+        except Exception as e:  # pylint: disable=broad-except
             log.debug("Image xref %s, error %s", xref, repr(e))
             errors += 1
         else:
             if result:
                 _, ext = result
-                yield pageno_for_xref[xref], xref, ext
+                yield pageno_for_xref[xref], XrefExt(xref, ext)
 
 
-def extract_images_generic(pike, root, log, options):
+def extract_images_generic(
+    pike: Pdf, root: Path, options
+) -> Tuple[List[Xref], List[Xref]]:
     """Extract any >=2bpp image we think we can improve"""
 
     jpegs = []
     pngs = []
-    for _, xref, ext in extract_images(pike, root, log, options, extract_image_generic):
-        log.debug('xref = %s ext = %s', xref, ext)
-        if ext == '.png':
-            pngs.append(xref)
-        elif ext == '.jpg':
-            jpegs.append(xref)
+    for _, xref_ext in extract_images(pike, root, options, extract_image_generic):
+        log.debug('%s', xref_ext)
+        if xref_ext.ext == '.png':
+            pngs.append(xref_ext.xref)
+        elif xref_ext.ext == '.jpg':
+            jpegs.append(xref_ext.xref)
     log.debug("Optimizable images: JPEGs: %s PNGs: %s", len(jpegs), len(pngs))
     return jpegs, pngs
 
 
-def extract_images_jbig2(pike, root, log, options):
+def extract_images_jbig2(pike: Pdf, root: Path, options) -> Dict[int, List[XrefExt]]:
     """Extract any bitonal image that we think we can improve as JBIG2"""
 
     jbig2_groups = defaultdict(list)
-    for pageno, xref, ext in extract_images(
-        pike, root, log, options, extract_image_jbig2
-    ):
+    for pageno, xref_ext in extract_images(pike, root, options, extract_image_jbig2):
         group = pageno // options.jbig2_page_group_size
-        jbig2_groups[group].append((xref, ext))
+        jbig2_groups[group].append(xref_ext)
 
     # Elide empty groups
     jbig2_groups = {
@@ -232,47 +290,59 @@ def extract_images_jbig2(pike, root, log, options):
     return jbig2_groups
 
 
-def _produce_jbig2_images(jbig2_groups, root, log, options):
+def _produce_jbig2_images(
+    jbig2_groups: Dict[int, List[XrefExt]], root: Path, options
+) -> None:
     """Produce JBIG2 images from their groups"""
 
-    def jbig2_group_futures(executor, root, groups):
+    def jbig2_group_args(root: Path, groups: Dict[int, List[XrefExt]]):
         for group, xref_exts in groups.items():
             prefix = f'group{group:08d}'
-            future = executor.submit(
-                jbig2enc.convert_group,
+            yield dict(
                 cwd=fspath(root),
                 infiles=(img_name(root, xref, ext) for xref, ext in xref_exts),
                 out_prefix=prefix,
             )
-            yield future
 
-    def jbig2_single_futures(executor, root, groups):
+    def jbig2_single_args(root, groups: Dict[int, List[XrefExt]]):
         for group, xref_exts in groups.items():
             prefix = f'group{group:08d}'
             # Second loop is to ensure multiple images per page are unpacked
             for n, xref_ext in enumerate(xref_exts):
                 xref, ext = xref_ext
-                future = executor.submit(
-                    jbig2enc.convert_single,
+                yield dict(
                     cwd=fspath(root),
                     infile=img_name(root, xref, ext),
                     outfile=root / f'{prefix}.{n:04d}',
                 )
-                yield future
+
+    def convert_generic(fn, kwargs_dict):
+        return fn(**kwargs_dict)
 
     if options.jbig2_page_group_size > 1:
-        jbig2_futures = jbig2_group_futures
+        jbig2_args = jbig2_group_args
+        jbig2_convert = partial(convert_generic, jbig2enc.convert_group)
     else:
-        jbig2_futures = jbig2_single_futures
+        jbig2_args = jbig2_single_args
+        jbig2_convert = partial(convert_generic, jbig2enc.convert_single)
 
-    with concurrent.futures.ThreadPoolExecutor(max_workers=options.jobs) as executor:
-        futures = jbig2_futures(executor, root, jbig2_groups)
-        for future in concurrent.futures.as_completed(futures):
-            proc = future.result()
-            log.debug(proc.stderr.decode())
+    exec_progress_pool(
+        use_threads=True,
+        max_workers=options.jobs,
+        tqdm_kwargs=dict(
+            total=len(jbig2_groups),
+            desc="JBIG2",
+            unit='item',
+            disable=not options.progress_bar,
+        ),
+        task=jbig2_convert,
+        task_arguments=jbig2_args(root, jbig2_groups),
+    )
 
 
-def convert_to_jbig2(pike, jbig2_groups, root, log, options):
+def convert_to_jbig2(
+    pike: Pdf, jbig2_groups: Dict[int, List[XrefExt]], root: Path, options
+) -> None:
     """Convert images to JBIG2 and insert into PDF.
 
     When the JBIG2 page group size is > 1 we do several JBIG2 images at once
@@ -286,7 +356,7 @@ def convert_to_jbig2(pike, jbig2_groups, root, log, options):
     and needs no dictionary. Currently this must be lossless JBIG2.
     """
 
-    _produce_jbig2_images(jbig2_groups, root, log, options)
+    _produce_jbig2_images(jbig2_groups, root, options)
 
     for group, xref_exts in jbig2_groups.items():
         prefix = f'group{group:08d}'
@@ -310,17 +380,19 @@ def convert_to_jbig2(pike, jbig2_groups, root, log, options):
             )
 
 
-def transcode_jpegs(pike, jpegs, root, log, options):
-    for xref in jpegs:
-        in_jpg = Path(jpg_name(root, xref))
+def transcode_jpegs(pike: Pdf, jpegs: Sequence[Xref], root: Path, options) -> None:
+    for xref in tqdm(
+        jpegs, desc="JPEGs", unit='image', disable=not options.progress_bar
+    ):
+        in_jpg = jpg_name(root, xref)
         opt_jpg = in_jpg.with_suffix('.opt.jpg')
 
         # This produces a debug warning from PIL
         # DEBUG:PIL.Image:Error closing: 'NoneType' object has no attribute
         # 'close'.  Seems to be mostly harmless
         # https://github.com/python-pillow/Pillow/issues/1144
-        with Image.open(fspath(in_jpg)) as im:
-            im.save(fspath(opt_jpg), optimize=True, quality=options.jpeg_quality)
+        with Image.open(in_jpg) as im:
+            im.save(opt_jpg, optimize=True, quality=options.jpeg_quality)
 
         if opt_jpg.stat().st_size > in_jpg.stat().st_size:
             log.debug("xref %s, jpeg, made larger - skip", xref)
@@ -331,29 +403,55 @@ def transcode_jpegs(pike, jpegs, root, log, options):
         im_obj.write(compdata.read(), filter=Name.DCTDecode)
 
 
-def transcode_pngs(pike, images, image_name_fn, root, log, options):
+def transcode_pngs(
+    pike: Pdf,
+    images: Sequence[Xref],
+    image_name_fn: Callable[[Path, Xref], Path],
+    root: Path,
+    options,
+) -> None:
+    modified: MutableSet[Xref] = set()
     if options.optimize >= 2:
         png_quality = (
             max(10, options.png_quality - 10),
             min(100, options.png_quality + 10),
         )
-        with concurrent.futures.ThreadPoolExecutor(
-            max_workers=options.jobs
-        ) as executor:
+
+        def pngquant_args():
             for xref in images:
                 log.debug(image_name_fn(root, xref))
-                executor.submit(
-                    pngquant.quantize,
+                yield (
                     image_name_fn(root, xref),
                     png_name(root, xref),
                     png_quality[0],
                     png_quality[1],
                 )
+                modified.add(xref)
 
-    for xref in images:
+        def pngquant_fn(args):
+            pngquant.quantize(*args)
+
+        exec_progress_pool(
+            use_threads=True,
+            max_workers=options.jobs,
+            tqdm_kwargs=dict(
+                desc="PNGs",
+                total=len(images),
+                unit='image',
+                disable=not options.progress_bar,
+            ),
+            task=pngquant_fn,
+            task_arguments=pngquant_args(),
+        )
+
+    for xref in modified:
         im_obj = pike.get_object(xref, 0)
         try:
-            compdata = leptonica.CompressedData.open(png_name(root, xref))
+            pix = leptonica.Pix.open(png_name(root, xref))
+            if pix.mode == '1':
+                compdata = pix.generate_pdf_ci_data(leptonica.lept.L_G4_ENCODE, 0)
+            else:
+                compdata = leptonica.CompressedData.open(png_name(root, xref))
         except leptonica.LeptonicaError as e:
             # Most likely this means file not found, i.e. quantize did not
             # produce an improved version
@@ -369,69 +467,89 @@ def transcode_pngs(pike, images, image_name_fn, root, log, options):
                 f"{len(compdata)} > {int(im_obj.stream_dict.Length)}"
             )
             continue
-
-        # When a PNG is inserted into a PDF, we more or less copy the IDAT section from
-        # the PDF and transfer the rest of the PNG headers to PDF image metadata.
-        # One thing we have to do is tell the PDF reader whether a predictor was used
-        # on the image before Flate encoding. (Typically one is.)
-        # According to Leptonica source, PDF readers don't actually need us
-        # to specify the correct predictor, they just need a value of either:
-        #   1 - no predictor
-        #   10-14 - there is a predictor
-        # Leptonica's compdata->predictor only tells TRUE or FALSE
-        # From there the PNG decoder can infer the rest from the file.
-        # In practice the predictor should be Paeth, 14, so we'll use that.
-        # See:
-        #   - PDF RM 7.4.4.4 Table 10
-        #   - https://github.com/DanBloomberg/leptonica/blob/master/src/pdfio2.c#L757
-        predictor = 14 if compdata.predictor > 0 else 1
-        dparms = Dictionary(Predictor=predictor)
-        if predictor > 1:
-            dparms.BitsPerComponent = compdata.bps  # Yes, this is redundant
-            dparms.Colors = compdata.spp
-            dparms.Columns = compdata.w
-
-        im_obj.BitsPerComponent = compdata.bps
-        im_obj.Width = compdata.w
-        im_obj.Height = compdata.h
-
-        if compdata.ncolors > 0:
-            # .ncolors is the number of colors in the palette, not the number of
-            # colors used in a true color image
-            palette_pdf_string = compdata.get_palette_pdf_string()
-            palette_data = pikepdf.Object.parse(palette_pdf_string)
-            palette_stream = pikepdf.Stream(pike, bytes(palette_data))
-            palette = [
-                Name.Indexed,
-                Name.DeviceRGB,
-                compdata.ncolors - 1,
-                palette_stream,
-            ]
-            cs = palette
-        else:
-            if compdata.spp == 1:
-                # PDF interprets binary-1 as black in 1bpp, but PNG sets
-                # black to 0 for 1bpp. Create a palette that informs the PDF
-                # of the mapping - seems cleaner to go this way but pikepdf
-                # needs to be patched to support it.
-                # palette = [Name.Indexed, Name.DeviceGray, 1, b"\xff\x00"]
-                # cs = palette
-                cs = Name.DeviceGray
-            elif compdata.spp == 3:
-                cs = Name.DeviceRGB
-            elif compdata.spp == 4:
-                cs = Name.DeviceCMYK
-        if compdata.bps == 1:
-            im_obj.Decode = [1, 0]  # Bit of a kludge but this inverts photometric too
-        im_obj.ColorSpace = cs
-        im_obj.write(compdata.read(), filter=Name.FlateDecode, decode_parms=dparms)
+        if compdata.type == leptonica.lept.L_FLATE_ENCODE:
+            rewrite_png(pike, im_obj, compdata)
+        elif compdata.type == leptonica.lept.L_G4_ENCODE:
+            rewrite_png_as_g4(pike, im_obj, compdata)
 
 
-def optimize(input_file, output_file, log, context):
+def rewrite_png_as_g4(pike: Pdf, im_obj: Object, compdata) -> None:
+    im_obj.BitsPerComponent = 1
+    im_obj.Width = compdata.w
+    im_obj.Height = compdata.h
 
-    options = context.get_options()
+    im_obj.write(compdata.read())
+
+    log.debug(f"PNG to G4 {im_obj.objgen}")
+    if Name.Predictor in im_obj:
+        del im_obj.Predictor
+    if Name.DecodeParms in im_obj:
+        del im_obj.DecodeParms
+    im_obj.DecodeParms = Dictionary(
+        K=-1, BlackIs1=bool(compdata.minisblack), Columns=compdata.w
+    )
+
+    im_obj.Filter = Name.CCITTFaxDecode
+    return
+
+
+def rewrite_png(pike: Pdf, im_obj: Object, compdata) -> None:
+    # When a PNG is inserted into a PDF, we more or less copy the IDAT section from
+    # the PDF and transfer the rest of the PNG headers to PDF image metadata.
+    # One thing we have to do is tell the PDF reader whether a predictor was used
+    # on the image before Flate encoding. (Typically one is.)
+    # According to Leptonica source, PDF readers don't actually need us
+    # to specify the correct predictor, they just need a value of either:
+    #   1 - no predictor
+    #   10-14 - there is a predictor
+    # Leptonica's compdata->predictor only tells TRUE or FALSE
+    # 10-14 means the actual predictor is specified in the data, so for any
+    # number >= 10 the PDF reader will use whatever the PNG data specifies.
+    # In practice Leptonica should use Paeth, 14, but 15 seems to be the
+    # designated value for "optimal". So we will use 15.
+    # See:
+    #   - PDF RM 7.4.4.4 Table 10
+    #   - https://github.com/DanBloomberg/leptonica/blob/master/src/pdfio2.c#L757
+    predictor = 15 if compdata.predictor > 0 else 1
+    dparms = Dictionary(Predictor=predictor)
+    if predictor > 1:
+        dparms.BitsPerComponent = compdata.bps  # Yes, this is redundant
+        dparms.Colors = compdata.spp
+        dparms.Columns = compdata.w
+
+    im_obj.BitsPerComponent = compdata.bps
+    im_obj.Width = compdata.w
+    im_obj.Height = compdata.h
+
+    log.debug(
+        f"PNG {im_obj.objgen}: palette={compdata.ncolors} spp={compdata.spp} bps={compdata.bps}"
+    )
+    if compdata.ncolors > 0:
+        # .ncolors is the number of colors in the palette, not the number of
+        # colors used in a true color image. The palette string is always
+        # given as RGB tuples even when the image is grayscale; see
+        # https://github.com/DanBloomberg/leptonica/blob/master/src/colormap.c#L2067
+        palette_pdf_string = compdata.get_palette_pdf_string()
+        palette_data = pikepdf.Object.parse(palette_pdf_string)
+        palette_stream = pikepdf.Stream(pike, bytes(palette_data))
+        palette = [Name.Indexed, Name.DeviceRGB, compdata.ncolors - 1, palette_stream]
+        cs = palette
+    else:
+        # ncolors == 0 means we are using a colorspace without a palette
+        if compdata.spp == 1:
+            cs = Name.DeviceGray
+        elif compdata.spp == 3:
+            cs = Name.DeviceRGB
+        elif compdata.spp == 4:
+            cs = Name.DeviceCMYK
+    im_obj.ColorSpace = cs
+    im_obj.write(compdata.read(), filter=Name.FlateDecode, decode_parms=dparms)
+
+
+def optimize(input_file: Path, output_file: Path, context, save_settings) -> None:
+    options = context.options
     if options.optimize == 0:
-        re_symlink(input_file, output_file, log)
+        safe_symlink(input_file, output_file)
         return
 
     if options.jpeg_quality == 0:
@@ -441,73 +559,88 @@ def optimize(input_file, output_file, log, context):
     if options.jbig2_page_group_size == 0:
         options.jbig2_page_group_size = 10 if options.jbig2_lossy else 1
 
-    pike = pikepdf.Pdf.open(input_file)
+    with pikepdf.Pdf.open(input_file) as pike:
+        root = output_file.parent / 'images'
+        root.mkdir(exist_ok=True)
 
-    root = Path(output_file).parent / 'images'
-    root.mkdir(exist_ok=True)
+        jpegs, pngs = extract_images_generic(pike, root, options)
+        transcode_jpegs(pike, jpegs, root, options)
+        # if options.optimize >= 2:
+        # Try pngifying the jpegs
+        #    transcode_pngs(pike, jpegs, jpg_name, root, options)
+        transcode_pngs(pike, pngs, png_name, root, options)
 
-    jpegs, pngs = extract_images_generic(pike, root, log, options)
-    transcode_jpegs(pike, jpegs, root, log, options)
-    # if options.optimize >= 2:
-    # Try pngifying the jpegs
-    #    transcode_pngs(pike, jpegs, jpg_name, root, log, options)
-    transcode_pngs(pike, pngs, png_name, root, log, options)
+        jbig2_groups = extract_images_jbig2(pike, root, options)
+        convert_to_jbig2(pike, jbig2_groups, root, options)
 
-    jbig2_groups = extract_images_jbig2(pike, root, log, options)
-    convert_to_jbig2(pike, jbig2_groups, root, log, options)
+        target_file = output_file.with_suffix('.opt.pdf')
+        pike.remove_unreferenced_resources()
+        pike.save(target_file, **save_settings)
 
-    target_file = Path(output_file).with_suffix('.opt.pdf')
-    pike.remove_unreferenced_resources()
-    pike.save(
-        target_file,
-        preserve_pdfa=True,
-        object_stream_mode=pikepdf.ObjectStreamMode.generate,
-    )
-
-    input_size = Path(input_file).stat().st_size
-    output_size = Path(target_file).stat().st_size
+    input_size = input_file.stat().st_size
+    output_size = target_file.stat().st_size
+    if output_size == 0:
+        raise OutputFileAccessError(
+            f"Output file not created after optimizing. We probably ran "
+            f"out of disk space in the temporary folder: {tempfile.gettempdir()}."
+        )
     ratio = input_size / output_size
     savings = 1 - output_size / input_size
     log.info(f"Optimize ratio: {ratio:.2f} savings: {(100 * savings):.1f}%")
 
     if savings < 0:
-        log.info("Optimize did not improve the file - discarded")
-        re_symlink(input_file, output_file, log)
+        log.info("Image optimization did not improve the file - discarded")
+        # We still need to save the file
+        with pikepdf.open(input_file) as pike:
+            pike.remove_unreferenced_resources()
+            pike.save(output_file, **save_settings)
     else:
-        re_symlink(target_file, output_file, log)
+        safe_symlink(target_file, output_file)
 
 
 def main(infile, outfile, level, jobs=1):
-    from tempfile import TemporaryDirectory
-    from shutil import copy
+    from shutil import copy  # pylint: disable=import-outside-toplevel
+    from tempfile import TemporaryDirectory  # pylint: disable=import-outside-toplevel
 
     class OptimizeOptions:
         """Emulate ocrmypdf's options"""
 
-        def __init__(self, jobs, optimize, jpeg_quality, png_quality, jb2lossy):
+        def __init__(
+            self, input_file, jobs, optimize_, jpeg_quality, png_quality, jb2lossy
+        ):
+            self.input_file = input_file
             self.jobs = jobs
-            self.optimize = optimize
+            self.optimize = optimize_
             self.jpeg_quality = jpeg_quality
             self.png_quality = png_quality
             self.jbig2_page_group_size = 0
             self.jbig2_lossy = jb2lossy
+            self.quiet = True
+            self.progress_bar = False
 
-    logging.basicConfig(level=logging.DEBUG)
-    log = logging.getLogger()
-
-    ctx = JobContext()
+    infile = Path(infile)
     options = OptimizeOptions(
+        input_file=infile,
         jobs=jobs,
-        optimize=int(level),
+        optimize_=int(level),
         jpeg_quality=0,  # Use default
         png_quality=0,
         jb2lossy=False,
     )
-    ctx.set_options(options)
 
     with TemporaryDirectory() as td:
+        context = PdfContext(options, td, infile, None, None)
         tmpout = Path(td) / 'out.pdf'
-        optimize(infile, tmpout, log, ctx)
+        optimize(
+            infile,
+            tmpout,
+            context,
+            dict(
+                compress_streams=True,
+                preserve_pdfa=True,
+                object_stream_mode=pikepdf.ObjectStreamMode.generate,
+            ),
+        )
         copy(fspath(tmpout), fspath(outfile))
 
 

src/ocrmypdf/pdfa.py

@@ -16,29 +16,16 @@
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
 """
-Generate a PDFMARK file for Ghostscript >= 9.14, for PDF/A conversion
-
-pdfmark is an extension to the Postscript language that describes some PDF
-features like bookmarks and annotations. It was originally specified Adobe
-Distiller, for Postscript to PDF conversion:
-https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/pdfmark_reference.pdf
-
-Ghostscript uses pdfmark for PDF to PDF/A conversion as well. To use Ghostscript
-to create a PDF/A, we need to create a pdfmark file with the necessary metadata.
-
-This takes care of the many version-specific bugs and pecularities in
-Ghostscript's handling of pdfmark.
-
+Utilities for PDF/A production and confirmation with Ghostspcript.
 """
 
-import os
-from binascii import hexlify
+import base64
 from pathlib import Path
 from string import Template
-
-import pkg_resources
+from typing import Dict, Union
 
 import pikepdf
+import pkg_resources
 
 ICC_PROFILE_RELPATH = 'data/sRGB.icc'
 
@@ -49,26 +36,13 @@ SRGB_ICC_PROFILE = pkg_resources.resource_filename('ocrmypdf', ICC_PROFILE_RELPA
 # files, from the Ghostscript documentation. Lines beginning with % are
 # comments. Python substitution variables have a '$' prefix.
 pdfa_def_template = u"""%!
-% Define entries in the document Info dictionary :
+% Define an ICC profile :
 /ICCProfile $icc_profile
 def
 
-% Define an ICC profile :
-
 [/_objdef {icc_PDFA} /type /stream /OBJ pdfmark
-[{icc_PDFA}
-<<
-  /N currentpagedevice /ProcessColorModel known {
-    currentpagedevice /ProcessColorModel get dup /DeviceGray eq
-    {pop 1} {
-      /DeviceRGB eq
-      {3}{4} ifelse
-    } ifelse
-  } {
-    (ERROR, unable to determine ProcessColorModel) == flush
-  } ifelse
->> /PUT pdfmark
-[{icc_PDFA} ICCProfile (r) file /PUT pdfmark
+[{icc_PDFA} << /N 3 >> /PUT pdfmark
+[{icc_PDFA} ICCProfile /PUT pdfmark
 
 % Define the output intent dictionary :
 
@@ -83,38 +57,38 @@ def
 """
 
 
-def generate_pdfa_ps(target_filename, icc='sRGB'):
-    """Create a Postscript pdfmark file for Ghostscript PDF/A conversion
+def generate_pdfa_ps(target_filename: Path, icc: str = 'sRGB'):
+    """Create a Postscript PDFMARK file for Ghostscript PDF/A conversion
 
-    A pdfmark file is a small Postscript program that provides some information
-    Ghostscript needs to perform PDF/A conversion. The only information we put
-    in specifies that we want the file to be a PDF/A, and we want to Ghostscript
-    to convert objects to the sRGB colorspace if it runs into any object that
-    it decides must be converted.
+    pdfmark is an extension to the Postscript language that describes some PDF
+    features like bookmarks and annotations. It was originally specified Adobe
+    Distiller, for Postscript to PDF conversion.
 
-    See the Adobe pdfmark Reference for details:
-    https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/pdfmark_reference.pdf
+    Ghostscript uses pdfmark for PDF to PDF/A conversion as well. To use Ghostscript
+    to create a PDF/A, we need to create a pdfmark file with the necessary metadata.
 
-    :param target_filename: filename to save
-    :param icc: ICC identifier such as 'sRGB'
+    This function takes care of the many version-specific bugs and pecularities in
+    Ghostscript's handling of pdfmark.
 
-    :returns: a string containing the entire pdfmark
+    The only information we put in specifies that we want the file to be a
+    PDF/A, and we want to Ghostscript to convert objects to the sRGB colorspace
+    if it runs into any object that it decides must be converted.
+
+    Arguments:
+        target_filename: filename to save
+        icc: ICC identifier such as 'sRGB'
+    References:
+        Adobe PDFMARK Reference: https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/pdfmark_reference.pdf
     """
     if icc == 'sRGB':
         icc_profile = SRGB_ICC_PROFILE
     else:
         raise NotImplementedError("Only supporting sRGB")
 
-    # pdfmark must contain the full path to the ICC profile, and pdfmark must be
-    # also encoded in ASCII. ocrmypdf can be installed anywhere, including to
-    # paths that have a non-ASCII character in the filename. Ghostscript
-    # accepts hex-encoded strings and converts them to byte strings, so
-    # we encode the path with fsencode() and use the hex representation.
-    # UTF-16 not accepted here. (Even though ASCII encodable is the usual case,
-    # do this always to avoid making it a rare conditional.)
-    bytes_icc_profile = os.fsencode(icc_profile)
-    hex_icc_profile = hexlify(bytes_icc_profile)
-    icc_profile = '<' + hex_icc_profile.decode('ascii') + '>'
+    # Read the ICC profile, encode as ASCII85 and convert to a string which we
+    # will insert in the .ps file
+    bytes_icc_profile = Path(icc_profile).read_bytes()
+    icc_profile = base64.a85encode(bytes_icc_profile, adobe=True).decode('ascii')
 
     t = Template(pdfa_def_template)
     ps = t.substitute(icc_profile=icc_profile, icc_identifier=icc)
@@ -122,28 +96,29 @@ def generate_pdfa_ps(target_filename, icc='sRGB'):
     # We should have encoded everything to pure ASCII by this point, and
     # to be safe, only allow ASCII in PostScript
     Path(target_filename).write_text(ps, encoding='ascii')
+    return target_filename
 
 
-def file_claims_pdfa(filename):
+def file_claims_pdfa(filename: Path):
     """Determines if the file claims to be PDF/A compliant
 
     This only checks if the XMP metadata contains a PDF/A marker. It does not
     do full PDF/A validation.
     """
 
-    pdf = pikepdf.open(filename)
-    pdfmeta = pdf.open_metadata()
-    if not pdfmeta.pdfa_status:
-        return {
-            'pass': False,
-            'output': 'pdf',
-            'conformance': 'No PDF/A metadata in XMP',
-        }
-    valid_part_conforms = {'1A', '1B', '2A', '2B', '2U', '3A', '3B', '3U'}
-    conformance = f'PDF/A-{pdfmeta.pdfa_status}'
-    pdfa_dict = {}
-    if pdfmeta.pdfa_status in valid_part_conforms:
-        pdfa_dict['pass'] = True
-        pdfa_dict['output'] = 'pdfa'
-    pdfa_dict['conformance'] = conformance
+    with pikepdf.open(filename) as pdf:
+        pdfmeta = pdf.open_metadata()
+        if not pdfmeta.pdfa_status:
+            return {
+                'pass': False,
+                'output': 'pdf',
+                'conformance': 'No PDF/A metadata in XMP',
+            }
+        valid_part_conforms = {'1A', '1B', '2A', '2B', '2U', '3A', '3B', '3U'}
+        conformance = f'PDF/A-{pdfmeta.pdfa_status}'
+        pdfa_dict: Dict[str, Union[str, bool]] = {}
+        if pdfmeta.pdfa_status in valid_part_conforms:
+            pdfa_dict['pass'] = True
+            pdfa_dict['output'] = 'pdfa'
+        pdfa_dict['conformance'] = conformance
     return pdfa_dict

src/ocrmypdf/pdfinfo/__init__.py

@@ -16,795 +16,4 @@
 # You should have received a copy of the GNU General Public License
 # along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
 
-from collections import namedtuple
-from decimal import Decimal
-from enum import Enum
-from math import hypot, isclose
-from os import fspath
-from pathlib import Path
-from unittest.mock import Mock
-from warnings import warn
-import re
-
-from pikepdf import PdfMatrix
-import pikepdf
-
-from . import ghosttext
-
-from ..exceptions import EncryptedPdfError, MissingDependencyError
-
-
-Colorspace = Enum('Colorspace', 'gray rgb cmyk lab icc index sep devn pattern jpeg2000')
-
-Encoding = Enum(
-    'Encoding', 'ccitt jpeg jpeg2000 jbig2 asciihex ascii85 lzw flate ' + 'runlength'
-)
-
-FRIENDLY_COLORSPACE = {
-    '/DeviceGray': Colorspace.gray,
-    '/CalGray': Colorspace.gray,
-    '/DeviceRGB': Colorspace.rgb,
-    '/CalRGB': Colorspace.rgb,
-    '/DeviceCMYK': Colorspace.cmyk,
-    '/Lab': Colorspace.lab,
-    '/ICCBased': Colorspace.icc,
-    '/Indexed': Colorspace.index,
-    '/Separation': Colorspace.sep,
-    '/DeviceN': Colorspace.devn,
-    '/Pattern': Colorspace.pattern,
-    '/G': Colorspace.gray,  # Abbreviations permitted in inline images
-    '/RGB': Colorspace.rgb,
-    '/CMYK': Colorspace.cmyk,
-    '/I': Colorspace.index,
-}
-
-FRIENDLY_ENCODING = {
-    '/CCITTFaxDecode': Encoding.ccitt,
-    '/DCTDecode': Encoding.jpeg,
-    '/JPXDecode': Encoding.jpeg2000,
-    '/JBIG2Decode': Encoding.jbig2,
-    '/CCF': Encoding.ccitt,  # Abbreviations permitted in inline images
-    '/DCT': Encoding.jpeg,
-    '/AHx': Encoding.asciihex,
-    '/A85': Encoding.ascii85,
-    '/LZW': Encoding.lzw,
-    '/Fl': Encoding.flate,
-    '/RL': Encoding.runlength,
-}
-
-FRIENDLY_COMP = {
-    Colorspace.gray: 1,
-    Colorspace.rgb: 3,
-    Colorspace.cmyk: 4,
-    Colorspace.lab: 3,
-    Colorspace.index: 1,
-}
-
-
-UNIT_SQUARE = (1.0, 0.0, 0.0, 1.0, 0.0, 0.0)
-
-
-def _is_unit_square(shorthand):
-    values = map(float, shorthand)
-    pairwise = zip(values, UNIT_SQUARE)
-    return all([isclose(a, b, rel_tol=1e-3) for a, b in pairwise])
-
-
-XobjectSettings = namedtuple('XobjectSettings', ['name', 'shorthand', 'stack_depth'])
-
-InlineSettings = namedtuple('InlineSettings', ['iimage', 'shorthand', 'stack_depth'])
-
-ContentsInfo = namedtuple(
-    'ContentsInfo', ['xobject_settings', 'inline_images', 'found_vector']
-)
-
-TextboxInfo = namedtuple('TextboxInfo', ['bbox', 'is_visible', 'is_corrupt'])
-
-
-class VectorInfo:
-    def __init__(self):
-        pass
-
-
-def _normalize_stack(graphobjs):
-    """Convert runs of qQ's in the stack into single graphobjs"""
-    for operands, operator in graphobjs:
-        operator = str(operator)
-        if re.match(r'Q*q+$', operator):  # Zero or more Q, one or more q
-            for char in operator:  # Split into individual
-                yield ([], char)  # Yield individual
-        else:
-            yield (operands, operator)
-
-
-def _interpret_contents(contentstream, initial_shorthand=UNIT_SQUARE):
-    """Interpret the PDF content stream.
-
-    The stack represents the state of the PDF graphics stack.  We are only
-    interested in the current transformation matrix (CTM) so we only track
-    this object; a full implementation would need to track many other items.
-
-    The CTM is initialized to the mapping from user space to device space.
-    PDF units are 1/72".  In a PDF viewer or printer this matrix is initialized
-    to the transformation to device space.  For example if set to
-    (1/72, 0, 0, 1/72, 0, 0) then all units would be calculated in inches.
-
-    Images are always considered to be (0, 0) -> (1, 1).  Before drawing an
-    image there should be a 'cm' that sets up an image coordinate system
-    where drawing from (0, 0) -> (1, 1) will draw on the desired area of the
-    page.
-
-    PDF units suit our needs so we initialize ctm to the identity matrix.
-
-    According to the PDF specification, the maximum stack depth is 32. Other
-    viewers tolerate some amount beyond this.  We issue a warning if the
-    stack depth exceeds the spec limit and set a hard limit beyond this to
-    bound our memory requirements.  If the stack underflows behavior is
-    undefined in the spec, but we just pretend nothing happened and leave the
-    CTM unchanged.
-    """
-
-    stack = []
-    ctm = PdfMatrix(initial_shorthand)
-    xobject_settings = []
-    inline_images = []
-    found_vector = False
-    vector_ops = set('S s f F f* B B* b b*'.split())
-    image_ops = set('BI ID EI q Q Do cm'.split())
-    operator_whitelist = ' '.join(vector_ops | image_ops)
-
-    for n, graphobj in enumerate(
-        _normalize_stack(
-            pikepdf.parse_content_stream(contentstream, operator_whitelist)
-        )
-    ):
-        operands, operator = graphobj
-        if operator == 'q':
-            stack.append(ctm)
-            if len(stack) > 32:  # See docstring
-                if len(stack) > 128:
-                    raise RuntimeError(
-                        "PDF graphics stack overflowed hard limit, operator %i" % n
-                    )
-                warn("PDF graphics stack overflowed spec limit")
-        elif operator == 'Q':
-            try:
-                ctm = stack.pop()
-            except IndexError:
-                # Keeping the ctm the same seems to be the only sensible thing
-                # to do. Just pretend nothing happened, keep calm and carry on.
-                warn("PDF graphics stack underflowed - PDF may be malformed")
-        elif operator == 'cm':
-            ctm = PdfMatrix(operands) @ ctm
-        elif operator == 'Do':
-            image_name = operands[0]
-            settings = XobjectSettings(
-                name=image_name, shorthand=ctm.shorthand, stack_depth=len(stack)
-            )
-            xobject_settings.append(settings)
-        elif operator == 'INLINE IMAGE':  # BI/ID/EI are grouped into this
-            iimage = operands[0]
-            inline = InlineSettings(
-                iimage=iimage, shorthand=ctm.shorthand, stack_depth=len(stack)
-            )
-            inline_images.append(inline)
-        elif operator in vector_ops:
-            found_vector = True
-
-    return ContentsInfo(
-        xobject_settings=xobject_settings,
-        inline_images=inline_images,
-        found_vector=found_vector,
-    )
-
-
-def _get_dpi(ctm_shorthand, image_size):
-    """Given the transformation matrix and image size, find the image DPI.
-
-    PDFs do not include image resolution information within image data.
-    Instead, the PDF page content stream describes the location where the
-    image will be rasterized, and the effective resolution is the ratio of the
-    pixel size to raster target size.
-
-    Normally a scanned PDF has the paper size set appropriately but this is
-    not guaranteed. The most common case is a cropped image will change the
-    page size (/CropBox) without altering the page content stream. That means
-    it is not sufficient to assume that the image fills the page, even though
-    that is the most common case.
-
-    A PDF image may be scaled (always), cropped, translated, rotated in place
-    to an arbitrary angle (rarely) and skewed. Only equal area mappings can
-    be expressed, that is, it is not necessary to consider distortions where
-    the effective DPI varies with position.
-
-    To determine the image scale, transform an offset axis vector v0 (0, 0),
-    width-axis vector v0 (1, 0), height-axis vector vh (0, 1) with the matrix,
-    which gives the dimensions of the image in PDF units. From there we can
-    compare to actual image dimensions. PDF uses
-    row vector * matrix_tranposed unlike the traditional
-    matrix * column vector.
-
-    The offset, width and height vectors can be combined in a matrix and
-    multiplied by the transform matrix. Then we want to calculated
-        magnitude(width_vector - offset_vector)
-    and
-        magnitude(height_vector - offset_vector)
-
-    When the above is worked out algebraically, the effect of translation
-    cancels out, and the vector magnitudes become functions of the nonzero
-    transformation matrix indices. The results of the derivation are used
-    in this code.
-
-    pdfimages -list does calculate the DPI in some way that is not completely
-    naive, but it does not get the DPI of rotated images right, so cannot be
-    used anymore to validate this. Photoshop works, or using Acrobat to
-    rotate the image back to normal.
-
-    It does not matter if the image is partially cropped, or even out of the
-    /MediaBox.
-
-    """
-
-    a, b, c, d, _, _ = ctm_shorthand
-
-    # Calculate the width and height of the image in PDF units
-    image_drawn_width = hypot(a, b)
-    image_drawn_height = hypot(c, d)
-
-    # The scale of the image is pixels per unit of default user space (1/72")
-    scale_w = image_size[0] / image_drawn_width
-    scale_h = image_size[1] / image_drawn_height
-
-    # DPI = scale * 72
-    dpi_w = scale_w * 72.0
-    dpi_h = scale_h * 72.0
-
-    return dpi_w, dpi_h
-
-
-class ImageInfo:
-    DPI_PREC = Decimal('1.000')
-
-    def __init__(self, *, name='', pdfimage=None, inline=None, shorthand=None):
-
-        self._name = str(name)
-        self._shorthand = shorthand
-
-        if inline is not None:
-            self._origin = 'inline'
-            pim = inline.iimage
-        elif pdfimage is not None:
-            self._origin = 'xobject'
-            pim = pikepdf.PdfImage(pdfimage)
-        self._width = pim.width
-        self._height = pim.height
-
-        # If /ImageMask is true, then this image is a stencil mask
-        # (Images that draw with this stencil mask will have a reference to
-        # it in their /Mask, but we don't actually need that information)
-        if pim.image_mask:
-            self._type = 'stencil'
-        else:
-            self._type = 'image'
-
-        self._bpc = int(pim.bits_per_component)
-        try:
-            self._enc = FRIENDLY_ENCODING.get(pim.filters[0], 'image')
-        except IndexError:
-            self._enc = '?'
-
-        try:
-            self._color = FRIENDLY_COLORSPACE.get(pim.colorspace, '?')
-        except NotImplementedError:
-            self._color = '?'
-        if self._enc == Encoding.jpeg2000:
-            self._color = Colorspace.jpeg2000
-
-        self._comp = FRIENDLY_COMP.get(self._color, '?')
-
-        # Bit of a hack... infer grayscale if component count is uncertain
-        # but encoding must be monochrome. This happens if a monochrome image
-        # has an ICC profile attached. Better solution would be to examine
-        # the ICC profile.
-        if self._comp == '?' and self._enc in (Encoding.ccitt, 'jbig2'):
-            self._comp = FRIENDLY_COMP[Colorspace.gray]
-
-    @property
-    def name(self):
-        return self._name
-
-    @property
-    def type_(self):
-        return self._type
-
-    @property
-    def width(self):
-        return self._width
-
-    @property
-    def height(self):
-        return self._height
-
-    @property
-    def bpc(self):
-        return self._bpc
-
-    @property
-    def color(self):
-        return self._color
-
-    @property
-    def comp(self):
-        return self._comp
-
-    @property
-    def enc(self):
-        return self._enc
-
-    @property
-    def xres(self):
-        return _get_dpi(self._shorthand, (self._width, self._height))[0]
-
-    @property
-    def yres(self):
-        return _get_dpi(self._shorthand, (self._width, self._height))[1]
-
-    def __repr__(self):
-        class_locals = {
-            attr: getattr(self, attr, None)
-            for attr in dir(self)
-            if not attr.startswith('_')
-        }
-        return (
-            "<ImageInfo '{name}' {type_} {width}x{height} {color} "
-            "{comp} {bpc} {enc} {xres}x{yres}>"
-        ).format(**class_locals)
-
-
-def _find_inline_images(contentsinfo):
-    "Find inline images in the contentstream"
-
-    for n, inline in enumerate(contentsinfo.inline_images):
-        yield ImageInfo(
-            name='inline-%02d' % n, shorthand=inline.shorthand, inline=inline
-        )
-
-
-def _image_xobjects(container):
-    """Search for all XObject-based images in the container
-
-    Usually the container is a page, but it could also be a Form XObject
-    that contains images. Filter out the Form XObjects which are dealt with
-    elsewhere.
-
-    Generate a sequence of tuples (image, xobj container), where container,
-    where xobj is the name of the object and image is the object itself,
-    since the object does not know its own name.
-
-    """
-
-    if '/Resources' not in container:
-        return
-    resources = container['/Resources']
-    if '/XObject' not in resources:
-        return
-    xobjs = resources['/XObject'].as_dict()
-    for xobj in xobjs:
-        candidate = xobjs[xobj]
-        if not '/Subtype' in candidate:
-            continue
-        if candidate['/Subtype'] == '/Image':
-            pdfimage = candidate
-            yield (pdfimage, xobj)
-
-
-def _find_regular_images(container, contentsinfo):
-    """Find images stored in the container's /Resources /XObject
-
-    Usually the container is a page, but it could also be a Form XObject
-    that contains images.
-
-    Generates images with their DPI at time of drawing.
-    """
-
-    for pdfimage, xobj in _image_xobjects(container):
-
-        # For each image that is drawn on this, check if we drawing the
-        # current image - yes this is O(n^2), but n == 1 almost always
-        for draw in contentsinfo.xobject_settings:
-            if draw.name != xobj:
-                continue
-
-            if draw.stack_depth == 0 and _is_unit_square(draw.shorthand):
-                # At least one PDF in the wild (and test suite) draws an image
-                # when the graphics stack depth is 0, meaning that the image
-                # gets drawn into a square of 1x1 PDF units (or 1/72",
-                # or 0.35 mm).  The equivalent DPI will be >100,000.  Exclude
-                # these from our DPI calculation for the page.
-                continue
-
-            yield ImageInfo(name=draw.name, pdfimage=pdfimage, shorthand=draw.shorthand)
-
-
-def _find_form_xobject_images(pdf, container, contentsinfo):
-    """Find any images that are in Form XObjects in the container
-
-    The container may be a page, or a parent Form XObject.
-
-    """
-    if '/Resources' not in container:
-        return
-    resources = container['/Resources']
-    if '/XObject' not in resources:
-        return
-    xobjs = resources['/XObject'].as_dict()
-    for xobj in xobjs:
-        candidate = xobjs[xobj]
-        if candidate['/Subtype'] != '/Form':
-            continue
-
-        form_xobject = candidate
-        for settings in contentsinfo.xobject_settings:
-            if settings.name != xobj:
-                continue
-
-            # Find images once for each time this Form XObject is drawn.
-            # This could be optimized to cache the multiple drawing events
-            # but in practice both Form XObjects and multiple drawing of the
-            # same object are both very rare.
-            ctm_shorthand = settings.shorthand
-            yield from _process_content_streams(
-                pdf=pdf, container=form_xobject, shorthand=ctm_shorthand
-            )
-
-
-def _process_content_streams(*, pdf, container, shorthand=None):
-    """Find all individual instances of images drawn in the container
-
-    Usually the container is a page, but it may also be a Form XObject.
-
-    On a typical page images are stored inline or as regular images
-    in an XObject.
-
-    Form XObjects may include inline images, XObject images,
-    and recursively, other Form XObjects; and also vector graphic objects.
-
-    Every instance of an image being drawn somewhere is flattened and
-    treated as a unique image, since if the same image is drawn multiple times
-    on one page it may be drawn at differing resolutions, and our objective
-    is to find the resolution at which the page can be rastered without
-    downsampling.
-
-    """
-
-    if container.get('/Type') == '/Page' and '/Contents' in container:
-        initial_shorthand = shorthand or UNIT_SQUARE
-    elif container.get('/Type') == '/XObject' and container['/Subtype'] == '/Form':
-        # Set the CTM to the state it was when the "Do" operator was
-        # encountered that is drawing this instance of the Form XObject
-        ctm = PdfMatrix(shorthand) if shorthand else PdfMatrix.identity()
-
-        # A Form XObject may provide its own matrix to map form space into
-        # user space. Get this if one exists
-        form_shorthand = container.get('/Matrix', PdfMatrix.identity())
-        form_matrix = PdfMatrix(form_shorthand)
-
-        # Concatenate form matrix with CTM to ensure CTM is correct for
-        # drawing this instance of the XObject
-        ctm = form_matrix @ ctm
-        initial_shorthand = ctm.shorthand
-    else:
-        return
-
-    contentsinfo = _interpret_contents(container, initial_shorthand)
-
-    if contentsinfo.found_vector:
-        yield VectorInfo()
-    yield from _find_inline_images(contentsinfo)
-    yield from _find_regular_images(container, contentsinfo)
-    yield from _find_form_xobject_images(pdf, container, contentsinfo)
-
-
-def _page_has_text(text_blocks, page_width, page_height):
-    """Smarter text detection that ignores text in margins"""
-
-    pw, ph = float(page_width), float(page_height)
-
-    margin_ratio = 0.125
-    interior_bbox = (
-        margin_ratio * pw,  # left
-        (1 - margin_ratio) * ph,  # top
-        (1 - margin_ratio) * pw,  # right
-        margin_ratio * ph,  # bottom  (first quadrant: bottom < top)
-    )
-
-    def rects_intersect(a, b):
-        """
-        Where (a,b) are 4-tuple rects (left-0, top-1, right-2, bottom-3)
-        https://stackoverflow.com/questions/306316/determine-if-two-rectangles-overlap-each-other
-        Formula assumes all boxes are in first quadrant
-        """
-        return a[0] < b[2] and a[2] > b[0] and a[1] > b[3] and a[3] < b[1]
-
-    has_text = False
-    for bbox in text_blocks:
-        if rects_intersect(bbox, interior_bbox):
-            has_text = True
-            break
-    return has_text
-
-
-def simplify_textboxes(miner, textbox_getter):
-    """Extract only limited content from text boxes
-
-    We do this to save memory and ensure that our objects are pickleable.
-    """
-    for box in textbox_getter(miner):
-        first_line = box._objs[0]
-        first_char = first_line._objs[0]
-
-        visible = first_char.rendermode != 3
-        corrupt = first_char.get_text() == '\ufffd'
-        yield TextboxInfo(box.bbox, visible, corrupt)
-
-
-def _pdf_get_pageinfo(pdf, pageno: int, infile, xmltext):
-    pageinfo = {}
-    pageinfo['pageno'] = pageno
-    pageinfo['images'] = []
-
-    page = pdf.pages[pageno]
-    mediabox = [Decimal(d) for d in page.MediaBox.as_list()]
-    width_pt = mediabox[2] - mediabox[0]
-    height_pt = mediabox[3] - mediabox[1]
-
-    if xmltext is not None:
-        bboxes = ghosttext.page_get_textblocks(
-            fspath(infile), pageno, xmltext=xmltext, height=height_pt
-        )
-        pageinfo['bboxes'] = bboxes
-    else:
-        # pdfminer required for this section
-        try:
-            from .layout import get_page_analysis, get_text_boxes
-        except ImportError:
-            raise MissingDependencyError(
-                "pdfminer is required for this feature. Your distribution "
-                "may not have installed it."
-            )
-        pscript5_mode = str(pdf.docinfo.get('/Creator')).startswith('PScript5')
-        miner = get_page_analysis(infile, pageno, pscript5_mode)
-        pageinfo['textboxes'] = list(simplify_textboxes(miner, get_text_boxes))
-        bboxes = (box.bbox for box in pageinfo['textboxes'])
-
-    pageinfo['has_text'] = _page_has_text(bboxes, width_pt, height_pt)
-
-    userunit = page.get('/UserUnit', Decimal(1.0))
-    if not isinstance(userunit, Decimal):
-        userunit = Decimal(userunit)
-    pageinfo['userunit'] = userunit
-    pageinfo['width_inches'] = width_pt * userunit / Decimal(72.0)
-    pageinfo['height_inches'] = height_pt * userunit / Decimal(72.0)
-
-    try:
-        pageinfo['rotate'] = int(page['/Rotate'])
-    except KeyError:
-        pageinfo['rotate'] = 0
-
-    userunit_shorthand = (userunit, 0, 0, userunit, 0, 0)
-    contentsinfo = [
-        ci
-        for ci in _process_content_streams(
-            pdf=pdf, container=page, shorthand=userunit_shorthand
-        )
-    ]
-
-    pageinfo['has_vector'] = False
-    if any(isinstance(ci, VectorInfo) for ci in contentsinfo):
-        pageinfo['has_vector'] = True
-
-    pageinfo['images'] = [im for im in contentsinfo if isinstance(im, ImageInfo)]
-    if pageinfo['images']:
-        xres = Decimal(max(image.xres for image in pageinfo['images']))
-        yres = Decimal(max(image.yres for image in pageinfo['images']))
-        pageinfo['xres'], pageinfo['yres'] = xres, yres
-        pageinfo['width_pixels'] = int(round(xres * pageinfo['width_inches']))
-        pageinfo['height_pixels'] = int(round(yres * pageinfo['height_inches']))
-
-    return pageinfo
-
-
-def _pdf_get_all_pageinfo(infile, detailed_analysis=False, log=None):
-    if not log:
-        log = Mock()
-
-    pdf = pikepdf.open(infile)
-    if pdf.is_encrypted:
-        raise EncryptedPdfError()  # Triggered by encryption with empty passwd
-    if detailed_analysis:
-        pages_xml = None
-    else:
-        pages_xml = ghosttext.extract_text_xml(infile, pdf, pageno=None, log=log)
-
-    pages = []
-    for n in range(len(pdf.pages)):
-        page_xml = pages_xml[n] if pages_xml else None
-        page = PageInfo(pdf, n, infile, page_xml, detailed_analysis)
-        pages.append(page)
-
-    return pages, pdf
-
-
-class PageInfo:
-    def __init__(self, pdf, pageno, infile, xmltext, detailed_analysis=False):
-        self._pageno = pageno
-        self._infile = infile
-        self._pageinfo = _pdf_get_pageinfo(pdf, pageno, infile, xmltext)
-        self._detailed_analysis = detailed_analysis
-
-    @property
-    def pageno(self):
-        return self._pageno
-
-    @property
-    def has_text(self):
-        return self._pageinfo['has_text']
-
-    @property
-    def has_corrupt_text(self):
-        if not self._detailed_analysis:
-            raise NotImplementedError('Did not do detailed analysis')
-        return any(tbox.is_corrupt for tbox in self._pageinfo['textboxes'])
-
-    @property
-    def has_vector(self):
-        return self._pageinfo['has_vector']
-
-    @property
-    def width_inches(self):
-        return self._pageinfo['width_inches']
-
-    @property
-    def height_inches(self):
-        return self._pageinfo['height_inches']
-
-    @property
-    def width_pixels(self):
-        return int(round(self.width_inches * self.xres))
-
-    @property
-    def height_pixels(self):
-        return int(round(self.height_inches * self.yres))
-
-    @property
-    def rotation(self):
-        return self._pageinfo.get('rotate', None)
-
-    @rotation.setter
-    def rotation(self, value):
-        if value in (0, 90, 180, 270, 360, -90, -180, -270):
-            self._pageinfo['rotate'] = value
-        else:
-            raise ValueError("rotation must be a cardinal angle")
-
-    @property
-    def images(self):
-        return self._pageinfo['images']
-
-    def get_textareas(self, visible=None, corrupt=None):
-        def predicate(obj, want_visible, want_corrupt):
-            result = True
-            if want_visible is not None:
-                if obj.is_visible != want_visible:
-                    result = False
-            if want_corrupt is not None:
-                if obj.is_corrupt != want_corrupt:
-                    result = False
-            return result
-
-        if 'textboxes' not in self._pageinfo:
-            if visible is not None and corrupt is not None:
-                raise NotImplementedError('Ghostscript textboxes cannot be classified')
-            return self._pageinfo['bboxes']
-
-        return (
-            obj.bbox
-            for obj in self._pageinfo['textboxes']
-            if predicate(obj, visible, corrupt)
-        )
-
-    @property
-    def xres(self):
-        return self._pageinfo.get('xres', None)
-
-    @property
-    def yres(self):
-        return self._pageinfo.get('yres', None)
-
-    @property
-    def userunit(self):
-        return self._pageinfo.get('userunit', None)
-
-    @property
-    def min_version(self):
-        if self.userunit is not None:
-            return '1.6'
-        else:
-            return '1.5'
-
-    def __repr__(self):
-        return (
-            '<PageInfo ' 'pageno={} {}"x{}" rotation={} res={}x{} has_text={}>'
-        ).format(
-            self.pageno,
-            self.width_inches,
-            self.height_inches,
-            self.rotation,
-            self.xres,
-            self.yres,
-            self.has_text,
-        )
-
-
-class PdfInfo:
-    """Get summary information about a PDF"""
-
-    def __init__(self, infile, detailed_page_analysis=False, log=None):
-        self._infile = infile
-        self._pages, pdf = _pdf_get_all_pageinfo(
-            infile, detailed_page_analysis, log=log
-        )
-        self._needs_rendering = pdf.root.get('/NeedsRendering', False)
-        self._has_acroform = '/AcroForm' in pdf.root
-
-    @property
-    def pages(self):
-        return self._pages
-
-    @property
-    def min_version(self):
-        # The minimum PDF is the maximum version that any particular page needs
-        return max(page.min_version for page in self.pages)
-
-    @property
-    def has_userunit(self):
-        return any(page.userunit != 1.0 for page in self.pages)
-
-    @property
-    def has_acroform(self):
-        return self._has_acroform
-
-    @property
-    def filename(self):
-        if not isinstance(self._infile, (str, Path)):
-            raise NotImplementedError("can't get filename from stream")
-        return self._infile
-
-    @property
-    def needs_rendering(self):
-        return self._needs_rendering
-
-    def __getitem__(self, item):
-        return self._pages[item]
-
-    def __len__(self):
-        return len(self._pages)
-
-    def __repr__(self):
-        return f"<PdfInfo('...'), page count={len(self)}>"
-
-
-def main():
-    import argparse
-
-    parser = argparse.ArgumentParser()
-    parser.add_argument('infile')
-    args = parser.parse_args()
-    info = _pdf_get_all_pageinfo(args.infile)
-    from pprint import pprint
-
-    pprint(info)
-
-
-if __name__ == '__main__':
-    main()
+from ocrmypdf.pdfinfo.info import Colorspace, Encoding, PdfInfo

src/ocrmypdf/pdfinfo/ghosttext.py

@@ -1,98 +0,0 @@
-# © 2018 James R. Barlow: github.com/jbarlow83
-#
-# This file is part of OCRmyPDF.
-#
-# OCRmyPDF is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# OCRmyPDF is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
-
-import re
-import xml.etree.ElementTree as ET
-
-from ..exec import ghostscript
-
-# Forgive me for I have sinned
-# I am using regular expressions to parse XML. However the XML in this case,
-# generated by Ghostscript, is self-consistent enough to be parseable.
-regex_remove_char_tags = re.compile(
-    br"""
-    <char\b
-    (?:   [^>]   # anything single character but >
-        | \">\"  # special case: trap ">"
-    )*
-    />           # terminate with '/>'
-""",
-    re.VERBOSE,
-)
-
-
-def page_get_textblocks(infile, pageno, xmltext, height):
-    """Get text boxes out of Ghostscript txtwrite xml"""
-
-    root = xmltext
-    if not hasattr(xmltext, 'findall'):
-        return []
-
-    def blocks():
-        for span in root.findall('.//span'):
-            bbox_str = span.attrib['bbox']
-            font_size = span.attrib['size']
-            pts = [int(pt) for pt in bbox_str.split()]
-            pts[1] = pts[1] - int(float(font_size) + 0.5)
-            bbox_topdown = tuple(pts)
-            bb = bbox_topdown
-            bbox_bottomup = (bb[0], height - bb[3], bb[2], height - bb[1])
-            yield bbox_bottomup
-
-    def joined_blocks():
-        prev = None
-        for bbox in blocks():
-            if prev is None:
-                prev = bbox
-            if bbox[1] == prev[1] and bbox[3] == prev[3]:
-                gap = prev[2] - bbox[0]
-                height = abs(bbox[3] - bbox[1])
-                if gap < height:
-                    # Join boxes
-                    prev = (prev[0], prev[1], bbox[2], bbox[3])
-                    continue
-            # yield previously joined bboxes and start anew
-            yield prev
-            prev = bbox
-        if prev is not None:
-            yield prev
-
-    return [block for block in joined_blocks()]
-
-
-def extract_text_xml(infile, pdf, pageno=None, log=None):
-    existing_text = ghostscript.extract_text(infile, pageno=None)
-    existing_text = regex_remove_char_tags.sub(b' ', existing_text)
-
-    try:
-        root = ET.fromstringlist([b'<document>\n', existing_text, b'</document>\n'])
-        page_xml = root.findall('page')
-    except ET.ParseError as e:
-        log.error(
-            "An error occurred while attempting to retrieve existing text in "
-            "the input file. Will attempt to continue assuming that there is "
-            "no existing text in the file. The error was:"
-        )
-        log.error(e)
-        page_xml = [None] * len(pdf.pages)
-
-    page_count_difference = len(pdf.pages) - len(page_xml)
-    if page_count_difference != 0:
-        log.error("The number of pages in the input file is inconsistent.")
-        if page_count_difference > 0:
-            page_xml.extend([None] * page_count_difference)
-    return page_xml

src/ocrmypdf/pdfinfo/info.py

@@ -0,0 +1,883 @@
+#!/usr/bin/env python3
+# © 2015 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import logging
+import re
+from collections import defaultdict, namedtuple
+from decimal import Decimal
+from enum import Enum
+from functools import partial
+from math import hypot, isclose
+from os import PathLike
+from pathlib import Path
+from typing import Any, Dict, List, Optional, Union
+from warnings import warn
+
+import pikepdf
+from pikepdf import PdfMatrix
+
+from ocrmypdf._concurrent import exec_progress_pool
+from ocrmypdf.exceptions import EncryptedPdfError
+from ocrmypdf.helpers import Resolution, available_cpu_count, pikepdf_enable_mmap
+from ocrmypdf.pdfinfo.layout import get_page_analysis, get_text_boxes
+
+logger = logging.getLogger()
+
+Colorspace = Enum('Colorspace', 'gray rgb cmyk lab icc index sep devn pattern jpeg2000')
+
+Encoding = Enum(
+    'Encoding', 'ccitt jpeg jpeg2000 jbig2 asciihex ascii85 lzw flate runlength'
+)
+
+FRIENDLY_COLORSPACE = {
+    '/DeviceGray': Colorspace.gray,
+    '/CalGray': Colorspace.gray,
+    '/DeviceRGB': Colorspace.rgb,
+    '/CalRGB': Colorspace.rgb,
+    '/DeviceCMYK': Colorspace.cmyk,
+    '/Lab': Colorspace.lab,
+    '/ICCBased': Colorspace.icc,
+    '/Indexed': Colorspace.index,
+    '/Separation': Colorspace.sep,
+    '/DeviceN': Colorspace.devn,
+    '/Pattern': Colorspace.pattern,
+    '/G': Colorspace.gray,  # Abbreviations permitted in inline images
+    '/RGB': Colorspace.rgb,
+    '/CMYK': Colorspace.cmyk,
+    '/I': Colorspace.index,
+}
+
+FRIENDLY_ENCODING = {
+    '/CCITTFaxDecode': Encoding.ccitt,
+    '/DCTDecode': Encoding.jpeg,
+    '/JPXDecode': Encoding.jpeg2000,
+    '/JBIG2Decode': Encoding.jbig2,
+    '/CCF': Encoding.ccitt,  # Abbreviations permitted in inline images
+    '/DCT': Encoding.jpeg,
+    '/AHx': Encoding.asciihex,
+    '/A85': Encoding.ascii85,
+    '/LZW': Encoding.lzw,
+    '/Fl': Encoding.flate,
+    '/RL': Encoding.runlength,
+}
+
+FRIENDLY_COMP = {
+    Colorspace.gray: 1,
+    Colorspace.rgb: 3,
+    Colorspace.cmyk: 4,
+    Colorspace.lab: 3,
+    Colorspace.index: 1,
+}
+
+
+UNIT_SQUARE = (1.0, 0.0, 0.0, 1.0, 0.0, 0.0)
+
+
+def _is_unit_square(shorthand):
+    values = map(float, shorthand)
+    pairwise = zip(values, UNIT_SQUARE)
+    return all(isclose(a, b, rel_tol=1e-3) for a, b in pairwise)
+
+
+XobjectSettings = namedtuple('XobjectSettings', ['name', 'shorthand', 'stack_depth'])
+
+InlineSettings = namedtuple('InlineSettings', ['iimage', 'shorthand', 'stack_depth'])
+
+ContentsInfo = namedtuple(
+    'ContentsInfo',
+    ['xobject_settings', 'inline_images', 'found_vector', 'found_text', 'name_index'],
+)
+
+TextboxInfo = namedtuple('TextboxInfo', ['bbox', 'is_visible', 'is_corrupt'])
+
+
+class VectorMarker:
+    pass
+
+
+class TextMarker:
+    pass
+
+
+def _normalize_stack(graphobjs):
+    """Convert runs of qQ's in the stack into single graphobjs"""
+    for operands, operator in graphobjs:
+        operator = str(operator)
+        if re.match(r'Q*q+$', operator):  # Zero or more Q, one or more q
+            for char in operator:  # Split into individual
+                yield ([], char)  # Yield individual
+        else:
+            yield (operands, operator)
+
+
+def _interpret_contents(contentstream, initial_shorthand=UNIT_SQUARE):
+    """Interpret the PDF content stream.
+
+    The stack represents the state of the PDF graphics stack.  We are only
+    interested in the current transformation matrix (CTM) so we only track
+    this object; a full implementation would need to track many other items.
+
+    The CTM is initialized to the mapping from user space to device space.
+    PDF units are 1/72".  In a PDF viewer or printer this matrix is initialized
+    to the transformation to device space.  For example if set to
+    (1/72, 0, 0, 1/72, 0, 0) then all units would be calculated in inches.
+
+    Images are always considered to be (0, 0) -> (1, 1).  Before drawing an
+    image there should be a 'cm' that sets up an image coordinate system
+    where drawing from (0, 0) -> (1, 1) will draw on the desired area of the
+    page.
+
+    PDF units suit our needs so we initialize ctm to the identity matrix.
+
+    According to the PDF specification, the maximum stack depth is 32. Other
+    viewers tolerate some amount beyond this.  We issue a warning if the
+    stack depth exceeds the spec limit and set a hard limit beyond this to
+    bound our memory requirements.  If the stack underflows behavior is
+    undefined in the spec, but we just pretend nothing happened and leave the
+    CTM unchanged.
+    """
+
+    stack = []
+    ctm = PdfMatrix(initial_shorthand)
+    xobject_settings = []
+    inline_images = []
+    name_index = defaultdict(lambda: [])
+    found_vector = False
+    found_text = False
+    vector_ops = set('S s f F f* B B* b b*'.split())
+    text_showing_ops = set("""TJ Tj " '""".split())
+    image_ops = set('BI ID EI q Q Do cm'.split())
+    operator_whitelist = ' '.join(vector_ops | text_showing_ops | image_ops)
+
+    for n, graphobj in enumerate(
+        _normalize_stack(
+            pikepdf.parse_content_stream(contentstream, operator_whitelist)
+        )
+    ):
+        operands, operator = graphobj
+        if operator == 'q':
+            stack.append(ctm)
+            if len(stack) > 32:  # See docstring
+                if len(stack) > 128:
+                    raise RuntimeError(
+                        "PDF graphics stack overflowed hard limit, operator %i" % n
+                    )
+                warn("PDF graphics stack overflowed spec limit")
+        elif operator == 'Q':
+            try:
+                ctm = stack.pop()
+            except IndexError:
+                # Keeping the ctm the same seems to be the only sensible thing
+                # to do. Just pretend nothing happened, keep calm and carry on.
+                warn("PDF graphics stack underflowed - PDF may be malformed")
+        elif operator == 'cm':
+            ctm = PdfMatrix(operands) @ ctm
+        elif operator == 'Do':
+            image_name = operands[0]
+            settings = XobjectSettings(
+                name=image_name, shorthand=ctm.shorthand, stack_depth=len(stack)
+            )
+            xobject_settings.append(settings)
+            name_index[image_name].append(settings)
+        elif operator == 'INLINE IMAGE':  # BI/ID/EI are grouped into this
+            iimage = operands[0]
+            inline = InlineSettings(
+                iimage=iimage, shorthand=ctm.shorthand, stack_depth=len(stack)
+            )
+            inline_images.append(inline)
+        elif operator in vector_ops:
+            found_vector = True
+        elif operator in text_showing_ops:
+            found_text = True
+
+    return ContentsInfo(
+        xobject_settings=xobject_settings,
+        inline_images=inline_images,
+        found_vector=found_vector,
+        found_text=found_text,
+        name_index=name_index,
+    )
+
+
+def _get_dpi(ctm_shorthand, image_size):
+    """Given the transformation matrix and image size, find the image DPI.
+
+    PDFs do not include image resolution information within image data.
+    Instead, the PDF page content stream describes the location where the
+    image will be rasterized, and the effective resolution is the ratio of the
+    pixel size to raster target size.
+
+    Normally a scanned PDF has the paper size set appropriately but this is
+    not guaranteed. The most common case is a cropped image will change the
+    page size (/CropBox) without altering the page content stream. That means
+    it is not sufficient to assume that the image fills the page, even though
+    that is the most common case.
+
+    A PDF image may be scaled (always), cropped, translated, rotated in place
+    to an arbitrary angle (rarely) and skewed. Only equal area mappings can
+    be expressed, that is, it is not necessary to consider distortions where
+    the effective DPI varies with position.
+
+    To determine the image scale, transform an offset axis vector v0 (0, 0),
+    width-axis vector v0 (1, 0), height-axis vector vh (0, 1) with the matrix,
+    which gives the dimensions of the image in PDF units. From there we can
+    compare to actual image dimensions. PDF uses
+    row vector * matrix_transposed unlike the traditional
+    matrix * column vector.
+
+    The offset, width and height vectors can be combined in a matrix and
+    multiplied by the transform matrix. Then we want to calculated
+        magnitude(width_vector - offset_vector)
+    and
+        magnitude(height_vector - offset_vector)
+
+    When the above is worked out algebraically, the effect of translation
+    cancels out, and the vector magnitudes become functions of the nonzero
+    transformation matrix indices. The results of the derivation are used
+    in this code.
+
+    pdfimages -list does calculate the DPI in some way that is not completely
+    naive, but it does not get the DPI of rotated images right, so cannot be
+    used anymore to validate this. Photoshop works, or using Acrobat to
+    rotate the image back to normal.
+
+    It does not matter if the image is partially cropped, or even out of the
+    /MediaBox.
+
+    """
+
+    a, b, c, d, _, _ = ctm_shorthand
+
+    # Calculate the width and height of the image in PDF units
+    image_drawn_width = hypot(a, b)
+    image_drawn_height = hypot(c, d)
+
+    # The scale of the image is pixels per unit of default user space (1/72")
+    scale_w = image_size[0] / image_drawn_width
+    scale_h = image_size[1] / image_drawn_height
+
+    # DPI = scale * 72
+    dpi_w = scale_w * 72.0
+    dpi_h = scale_h * 72.0
+
+    return Resolution(dpi_w, dpi_h)
+
+
+class ImageInfo:
+    DPI_PREC = Decimal('1.000')
+
+    def __init__(self, *, name='', pdfimage=None, inline=None, shorthand=None):
+
+        self._name = str(name)
+        self._shorthand = shorthand
+
+        if inline is not None:
+            self._origin = 'inline'
+            pim = inline.iimage
+        elif pdfimage is not None:
+            self._origin = 'xobject'
+            pim = pikepdf.PdfImage(pdfimage)
+        self._width = pim.width
+        self._height = pim.height
+
+        # If /ImageMask is true, then this image is a stencil mask
+        # (Images that draw with this stencil mask will have a reference to
+        # it in their /Mask, but we don't actually need that information)
+        if pim.image_mask:
+            self._type = 'stencil'
+        else:
+            self._type = 'image'
+
+        self._bpc = int(pim.bits_per_component)
+        try:
+            self._enc = FRIENDLY_ENCODING.get(pim.filters[0], 'image')
+        except IndexError:
+            self._enc = '?'
+
+        try:
+            self._color = FRIENDLY_COLORSPACE.get(pim.colorspace, '?')
+        except NotImplementedError:
+            self._color = '?'
+        if self._enc == Encoding.jpeg2000:
+            self._color = Colorspace.jpeg2000
+
+        if self._color == Colorspace.icc:
+            # Check the ICC profile to determine actual colorspace
+            pim_icc = pim.icc
+            if pim_icc.profile.xcolor_space == 'GRAY':
+                self._comp = 1
+            elif pim_icc.profile.xcolor_space == 'CMYK':
+                self._comp = 4
+            else:
+                self._comp = 3
+        else:
+            self._comp = FRIENDLY_COMP.get(self._color, '?')
+
+            # Bit of a hack... infer grayscale if component count is uncertain
+            # but encoding only supports monochrome.
+            if self._comp == '?' and self._enc in (Encoding.ccitt, Encoding.jbig2):
+                self._comp = FRIENDLY_COMP[Colorspace.gray]
+
+    @property
+    def name(self):
+        return self._name
+
+    @property
+    def type_(self):
+        return self._type
+
+    @property
+    def width(self):
+        return self._width
+
+    @property
+    def height(self):
+        return self._height
+
+    @property
+    def bpc(self):
+        return self._bpc
+
+    @property
+    def color(self):
+        return self._color
+
+    @property
+    def comp(self):
+        return self._comp
+
+    @property
+    def enc(self):
+        return self._enc
+
+    @property
+    def dpi(self):
+        return _get_dpi(self._shorthand, (self._width, self._height))
+
+    def __repr__(self):
+        class_locals = {
+            attr: getattr(self, attr, None)
+            for attr in dir(self)
+            if not attr.startswith('_')
+        }
+        return (
+            "<ImageInfo '{name}' {type_} {width}x{height} {color} "
+            "{comp} {bpc} {enc} {dpi}>"
+        ).format(**class_locals)
+
+
+def _find_inline_images(contentsinfo):
+    "Find inline images in the contentstream"
+
+    for n, inline in enumerate(contentsinfo.inline_images):
+        yield ImageInfo(
+            name='inline-%02d' % n, shorthand=inline.shorthand, inline=inline
+        )
+
+
+def _image_xobjects(container):
+    """Search for all XObject-based images in the container
+
+    Usually the container is a page, but it could also be a Form XObject
+    that contains images. Filter out the Form XObjects which are dealt with
+    elsewhere.
+
+    Generate a sequence of tuples (image, xobj container), where container,
+    where xobj is the name of the object and image is the object itself,
+    since the object does not know its own name.
+
+    """
+
+    if '/Resources' not in container:
+        return
+    resources = container['/Resources']
+    if '/XObject' not in resources:
+        return
+    xobjs = resources['/XObject'].as_dict()
+    for xobj in xobjs:
+        candidate = xobjs[xobj]
+        if not '/Subtype' in candidate:
+            continue
+        if candidate['/Subtype'] == '/Image':
+            pdfimage = candidate
+            yield (pdfimage, xobj)
+
+
+def _find_regular_images(container, contentsinfo):
+    """Find images stored in the container's /Resources /XObject
+
+    Usually the container is a page, but it could also be a Form XObject
+    that contains images.
+
+    Generates images with their DPI at time of drawing.
+    """
+
+    for pdfimage, xobj in _image_xobjects(container):
+        if xobj not in contentsinfo.name_index:
+            continue
+        for draw in contentsinfo.name_index[xobj]:
+            if draw.stack_depth == 0 and _is_unit_square(draw.shorthand):
+                # At least one PDF in the wild (and test suite) draws an image
+                # when the graphics stack depth is 0, meaning that the image
+                # gets drawn into a square of 1x1 PDF units (or 1/72",
+                # or 0.35 mm).  The equivalent DPI will be >100,000.  Exclude
+                # these from our DPI calculation for the page.
+                continue
+
+            yield ImageInfo(name=draw.name, pdfimage=pdfimage, shorthand=draw.shorthand)
+
+
+def _find_form_xobject_images(pdf, container, contentsinfo):
+    """Find any images that are in Form XObjects in the container
+
+    The container may be a page, or a parent Form XObject.
+
+    """
+    if '/Resources' not in container:
+        return
+    resources = container['/Resources']
+    if '/XObject' not in resources:
+        return
+    xobjs = resources['/XObject'].as_dict()
+    for xobj in xobjs:
+        candidate = xobjs[xobj]
+        if candidate['/Subtype'] != '/Form':
+            continue
+
+        form_xobject = candidate
+        for settings in contentsinfo.xobject_settings:
+            if settings.name != xobj:
+                continue
+
+            # Find images once for each time this Form XObject is drawn.
+            # This could be optimized to cache the multiple drawing events
+            # but in practice both Form XObjects and multiple drawing of the
+            # same object are both very rare.
+            ctm_shorthand = settings.shorthand
+            yield from _process_content_streams(
+                pdf=pdf, container=form_xobject, shorthand=ctm_shorthand
+            )
+
+
+def _process_content_streams(*, pdf, container, shorthand=None):
+    """Find all individual instances of images drawn in the container
+
+    Usually the container is a page, but it may also be a Form XObject.
+
+    On a typical page images are stored inline or as regular images
+    in an XObject.
+
+    Form XObjects may include inline images, XObject images,
+    and recursively, other Form XObjects; and also vector graphic objects.
+
+    Every instance of an image being drawn somewhere is flattened and
+    treated as a unique image, since if the same image is drawn multiple times
+    on one page it may be drawn at differing resolutions, and our objective
+    is to find the resolution at which the page can be rastered without
+    downsampling.
+
+    """
+
+    if container.get('/Type') == '/Page' and '/Contents' in container:
+        initial_shorthand = shorthand or UNIT_SQUARE
+    elif container.get('/Type') == '/XObject' and container['/Subtype'] == '/Form':
+        # Set the CTM to the state it was when the "Do" operator was
+        # encountered that is drawing this instance of the Form XObject
+        ctm = PdfMatrix(shorthand) if shorthand else PdfMatrix.identity()
+
+        # A Form XObject may provide its own matrix to map form space into
+        # user space. Get this if one exists
+        form_shorthand = container.get('/Matrix', PdfMatrix.identity())
+        form_matrix = PdfMatrix(form_shorthand)
+
+        # Concatenate form matrix with CTM to ensure CTM is correct for
+        # drawing this instance of the XObject
+        ctm = form_matrix @ ctm
+        initial_shorthand = ctm.shorthand
+    else:
+        return
+
+    contentsinfo = _interpret_contents(container, initial_shorthand)
+
+    if contentsinfo.found_vector:
+        yield VectorMarker()
+    if contentsinfo.found_text:
+        yield TextMarker()
+    yield from _find_inline_images(contentsinfo)
+    yield from _find_regular_images(container, contentsinfo)
+    yield from _find_form_xobject_images(pdf, container, contentsinfo)
+
+
+def _page_has_text(text_blocks, page_width, page_height) -> bool:
+    """Smarter text detection that ignores text in margins"""
+
+    pw, ph = float(page_width), float(page_height)
+
+    margin_ratio = 0.125
+    interior_bbox = (
+        margin_ratio * pw,  # left
+        (1 - margin_ratio) * ph,  # top
+        (1 - margin_ratio) * pw,  # right
+        margin_ratio * ph,  # bottom  (first quadrant: bottom < top)
+    )
+
+    def rects_intersect(a, b):
+        """
+        Where (a,b) are 4-tuple rects (left-0, top-1, right-2, bottom-3)
+        https://stackoverflow.com/questions/306316/determine-if-two-rectangles-overlap-each-other
+        Formula assumes all boxes are in first quadrant
+        """
+        return a[0] < b[2] and a[2] > b[0] and a[1] > b[3] and a[3] < b[1]
+
+    has_text = False
+    for bbox in text_blocks:
+        if rects_intersect(bbox, interior_bbox):
+            has_text = True
+            break
+    return has_text
+
+
+def simplify_textboxes(miner, textbox_getter):
+    """Extract only limited content from text boxes
+
+    We do this to save memory and ensure that our objects are pickleable.
+    """
+    for box in textbox_getter(miner):
+        first_line = box._objs[0]
+        first_char = first_line._objs[0]
+
+        visible = first_char.rendermode != 3
+        corrupt = first_char.get_text() == '\ufffd'
+        yield TextboxInfo(box.bbox, visible, corrupt)
+
+
+def _pdf_get_pageinfo(
+    pdf, pageno: int, infile: PathLike, check_pages, detailed_analysis: bool
+):
+    pageinfo: Dict[str, Any] = {}
+    pageinfo['pageno'] = pageno
+    pageinfo['images'] = []
+
+    page = pdf.pages[pageno]
+    mediabox = [Decimal(d) for d in page.MediaBox.as_list()]
+    width_pt = mediabox[2] - mediabox[0]
+    height_pt = mediabox[3] - mediabox[1]
+
+    check_this_page = pageno in check_pages
+
+    if check_this_page and detailed_analysis:
+        pscript5_mode = str(pdf.docinfo.get('/Creator')).startswith('PScript5')
+        miner = get_page_analysis(infile, pageno, pscript5_mode)
+        pageinfo['textboxes'] = list(simplify_textboxes(miner, get_text_boxes))
+        bboxes = (box.bbox for box in pageinfo['textboxes'])
+
+        pageinfo['has_text'] = _page_has_text(bboxes, width_pt, height_pt)
+    else:
+        pageinfo['textboxes'] = []
+        pageinfo['has_text'] = None  # i.e. "no information"
+
+    userunit = page.get('/UserUnit', Decimal(1.0))
+    if not isinstance(userunit, Decimal):
+        userunit = Decimal(userunit)
+    pageinfo['userunit'] = userunit
+    pageinfo['width_inches'] = width_pt * userunit / Decimal(72.0)
+    pageinfo['height_inches'] = height_pt * userunit / Decimal(72.0)
+
+    try:
+        pageinfo['rotate'] = int(page['/Rotate'])
+    except KeyError:
+        pageinfo['rotate'] = 0
+
+    userunit_shorthand = (userunit, 0, 0, userunit, 0, 0)
+
+    if check_this_page:
+        pageinfo['has_vector'] = False
+        pageinfo['has_text'] = False
+        pageinfo['images'] = []
+        for ci in _process_content_streams(
+            pdf=pdf, container=page, shorthand=userunit_shorthand
+        ):
+            if isinstance(ci, VectorMarker):
+                pageinfo['has_vector'] = True
+            elif isinstance(ci, TextMarker):
+                pageinfo['has_text'] = True
+            elif isinstance(ci, ImageInfo):
+                pageinfo['images'].append(ci)
+            else:
+                raise NotImplementedError()
+    else:
+        pageinfo['has_vector'] = None  # i.e. "no information"
+        pageinfo['has_text'] = None
+        pageinfo['images'] = None
+
+    if pageinfo['images']:
+        dpi = Resolution(0.0, 0.0).take_max(image.dpi for image in pageinfo['images'])
+        pageinfo['dpi'] = dpi
+        pageinfo['width_pixels'] = int(round(dpi.x * float(pageinfo['width_inches'])))
+        pageinfo['height_pixels'] = int(round(dpi.y * float(pageinfo['height_inches'])))
+
+    return pageinfo
+
+
+worker_pdf = None
+
+
+def _pdf_pageinfo_sync_init(infile):
+    global worker_pdf  # pylint: disable=global-statement
+    pikepdf_enable_mmap()
+    worker_pdf = pikepdf.open(infile)
+
+
+def _pdf_pageinfo_sync(args):
+    global worker_pdf  # pylint: disable=global-statement
+    pageno, infile, check_pages, detailed_analysis = args
+    page = PageInfo(worker_pdf, pageno, infile, check_pages, detailed_analysis)
+    return page
+
+
+def _pdf_pageinfo_concurrent(
+    pdf, infile, progbar, max_workers, check_pages, detailed_analysis=False
+):
+    pages = [None] * len(pdf.pages)
+
+    def update_pageinfo(result, pbar):
+        page = result
+        pages[page.pageno] = page
+        pbar.update()
+
+    if max_workers is None:
+        max_workers = available_cpu_count()
+
+    total = len(pdf.pages)
+    contexts = ((n, infile, check_pages, detailed_analysis) for n in range(total))
+
+    use_threads = False  # No performance gain if threaded due to GIL
+    n_workers = min(1 + len(pages) // 4, max_workers)
+    if n_workers == 1:
+        # But if we decided on only one worker, there is no point in using
+        # a separate process.
+        use_threads = True
+
+    exec_progress_pool(
+        use_threads=use_threads,
+        max_workers=n_workers,
+        tqdm_kwargs=dict(
+            total=total, desc="Scanning contents", unit='page', disable=not progbar
+        ),
+        task_initializer=partial(_pdf_pageinfo_sync_init, infile),
+        task=_pdf_pageinfo_sync,
+        task_arguments=contexts,
+        task_finished=update_pageinfo,
+    )
+    return pages
+
+
+class PageInfo:
+    def __init__(self, pdf, pageno, infile, check_pages, detailed_analysis=False):
+        self._pageno = pageno
+        self._infile = infile
+        self._detailed_analysis = detailed_analysis
+        self._pageinfo = _pdf_get_pageinfo(
+            pdf, pageno, infile, check_pages, detailed_analysis
+        )
+
+    @property
+    def pageno(self) -> int:
+        return self._pageno
+
+    @property
+    def has_text(self) -> bool:
+        return self._pageinfo['has_text']
+
+    @property
+    def has_corrupt_text(self) -> bool:
+        if not self._detailed_analysis:
+            raise NotImplementedError('Did not do detailed analysis')
+        return any(tbox.is_corrupt for tbox in self._pageinfo['textboxes'])
+
+    @property
+    def has_vector(self) -> bool:
+        return self._pageinfo['has_vector']
+
+    @property
+    def width_inches(self) -> Decimal:
+        return self._pageinfo['width_inches']
+
+    @property
+    def height_inches(self) -> Decimal:
+        return self._pageinfo['height_inches']
+
+    @property
+    def width_pixels(self) -> int:
+        return int(round(float(self.width_inches) * self.dpi.x))
+
+    @property
+    def height_pixels(self) -> int:
+        return int(round(float(self.height_inches) * self.dpi.y))
+
+    @property
+    def rotation(self) -> int:
+        return self._pageinfo.get('rotate', None)
+
+    @rotation.setter
+    def rotation(self, value):
+        if value in (0, 90, 180, 270, 360, -90, -180, -270):
+            self._pageinfo['rotate'] = value
+        else:
+            raise ValueError("rotation must be a cardinal angle")
+
+    @property
+    def images(self):
+        return self._pageinfo['images']
+
+    def get_textareas(
+        self, visible: Optional[bool] = None, corrupt: Optional[bool] = None
+    ):
+        def predicate(obj, want_visible, want_corrupt):
+            result = True
+            if want_visible is not None:
+                if obj.is_visible != want_visible:
+                    result = False
+            if want_corrupt is not None:
+                if obj.is_corrupt != want_corrupt:
+                    result = False
+            return result
+
+        if 'textboxes' not in self._pageinfo:
+            if visible is not None and corrupt is not None:
+                raise NotImplementedError('Incomplete information on textboxes')
+            return self._pageinfo['bboxes']
+
+        return (
+            obj.bbox
+            for obj in self._pageinfo['textboxes']
+            if predicate(obj, visible, corrupt)
+        )
+
+    @property
+    def dpi(self) -> Resolution:
+        return self._pageinfo.get('dpi', Resolution(0.0, 0.0))
+
+    @property
+    def userunit(self) -> Decimal:
+        return self._pageinfo.get('userunit', None)
+
+    @property
+    def min_version(self) -> str:
+        if self.userunit is not None:
+            return '1.6'
+        else:
+            return '1.5'
+
+    def __repr__(self):
+        return (
+            f'<PageInfo '
+            f'pageno={self.pageno} {self.width_inches}"x{self.height_inches}" '
+            f'rotation={self.rotation} dpi={self.dpi} has_text={self.has_text}>'
+        )
+
+
+class PdfInfo:
+    """Get summary information about a PDF"""
+
+    def __init__(
+        self,
+        infile,
+        detailed_analysis: bool = False,
+        progbar: bool = False,
+        max_workers: int = None,
+        check_pages=None,
+    ):
+        self._infile = infile
+        if check_pages is None:
+            check_pages = range(0, 1_000_000_000)
+
+        with pikepdf.open(infile) as pdf:
+            if pdf.is_encrypted:
+                raise EncryptedPdfError()  # Triggered by encryption with empty passwd
+            self._pages = _pdf_pageinfo_concurrent(
+                pdf,
+                infile,
+                progbar,
+                max_workers,
+                check_pages=check_pages,
+                detailed_analysis=detailed_analysis,
+            )
+            self._needs_rendering = pdf.root.get('/NeedsRendering', False)
+            self._has_acroform = False
+            if '/AcroForm' in pdf.root:
+                if len(pdf.root.AcroForm.get('/Fields', [])) > 0:
+                    self._has_acroform = True
+                elif '/XFA' in pdf.root.AcroForm:
+                    self._has_acroform = True
+
+    @property
+    def pages(self):
+        return self._pages
+
+    @property
+    def min_version(self) -> str:
+        # The minimum PDF is the maximum version that any particular page needs
+        return max(page.min_version for page in self.pages)
+
+    @property
+    def has_userunit(self) -> bool:
+        return any(page.userunit != 1.0 for page in self.pages)
+
+    @property
+    def has_acroform(self) -> bool:
+        return self._has_acroform
+
+    @property
+    def filename(self) -> Union[str, Path]:
+        if not isinstance(self._infile, (str, Path)):
+            raise NotImplementedError("can't get filename from stream")
+        return self._infile
+
+    @property
+    def needs_rendering(self) -> bool:
+        return self._needs_rendering
+
+    def __getitem__(self, item) -> PageInfo:
+        return self._pages[item]
+
+    def __len__(self):
+        return len(self._pages)
+
+    def __repr__(self):
+        return f"<PdfInfo('...'), page count={len(self)}>"
+
+
+def main():
+    import argparse  # pylint: disable=import-outside-toplevel
+    from pprint import pprint  # pylint: disable=import-outside-toplevel
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('infile')
+    args = parser.parse_args()
+    pdfinfo = PdfInfo(args.infile)
+
+    pprint(pdfinfo)
+    for page in pdfinfo.pages:
+        pprint(page)
+        for im in page.images:
+            pprint(im)
+
+
+if __name__ == '__main__':
+    main()

src/ocrmypdf/pdfinfo/layout.py

@@ -20,66 +20,21 @@ from math import copysign
 from pathlib import Path
 from unittest.mock import patch
 
+import pdfminer
 import pdfminer.encodingdb
 import pdfminer.pdfdevice
 import pdfminer.pdfinterp
 from pdfminer.converter import PDFLayoutAnalyzer
-from pdfminer.glyphlist import glyphname2unicode
 from pdfminer.layout import LAParams, LTChar, LTPage, LTTextBox
 from pdfminer.pdfdocument import PDFTextExtractionNotAllowed
-from pdfminer.pdffont import PDFFont, PDFSimpleFont, PDFUnicodeNotDefined
+from pdfminer.pdffont import PDFSimpleFont, PDFUnicodeNotDefined
 from pdfminer.pdfpage import PDFPage
 from pdfminer.utils import bbox2str, matrix2str
 
-from ..exceptions import EncryptedPdfError
+from ocrmypdf.exceptions import EncryptedPdfError
 
 STRIP_NAME = re.compile(r'[0-9]+')
 
-#
-# Unconditional pdfminer patches
-#
-
-
-def name2unicode(name):
-    """Fix pdfminer's name2unicode function
-
-    Font cids that are mapped to names of the form /g123 seem to be, by convention
-    characters with no corresponding Unicode entry. These can be subsetted fonts
-    or symbolic fonts. There seems to be no way to map /g123 fonts to Unicode,
-    barring a ToUnicode data structure.
-    """
-    if name in glyphname2unicode:
-        return glyphname2unicode[name]
-    if name.startswith('g') or name.startswith('a'):
-        raise KeyError(name)
-    if name.startswith('uni'):
-        try:
-            return chr(int(name[3:], 16))
-        except ValueError:  # Not hexadecimal
-            raise KeyError(name)
-    m = STRIP_NAME.search(name)
-    if not m:
-        raise KeyError(name)
-    return chr(int(m.group(0)))
-
-
-pdfminer.encodingdb.name2unicode = name2unicode
-
-original_PDFFont_init = PDFFont.__init__
-
-
-def PDFFont__init__(self, descriptor, widths, default_width=None):
-    original_PDFFont_init(self, descriptor, widths, default_width)
-    # PDF spec says descent should be negative
-    # A font with a positive descent implies it floats entirely above the
-    # baseline, i.e. it's not really a baseline anymore. I have fonts that
-    # claim a positive descent, but treating descent as positive always seems
-    # to misposition text.
-    if self.descent > 0:
-        self.descent = -self.descent
-
-
-PDFFont.__init__ = PDFFont__init__
 
 original_PDFSimpleFont_init = PDFSimpleFont.__init__
 
@@ -97,6 +52,7 @@ def PDFSimpleFont__init__(self, descriptor, widths, spec):
 
 
 PDFSimpleFont.__init__ = PDFSimpleFont__init__
+
 #
 # pdfminer patches when creator is PScript5.dll
 #
@@ -172,6 +128,7 @@ class LTStateAwareChar(LTChar):
             - the Unicode mapping is known, and both have the same render mode
             - the Unicode mapping is unknown but both are part of the same font
         """
+        # pylint: disable=protected-access
         both_unicode_mapped = isinstance(self._text, str) and isinstance(obj._text, str)
         try:
             if both_unicode_mapped:
@@ -184,7 +141,7 @@ class LTStateAwareChar(LTChar):
 
     def get_text(self):
         if isinstance(self._text, tuple):
-            return '�'
+            return '\ufffd'  # standard 'Unknown symbol'
         return self._text
 
     def __repr__(self):
@@ -206,6 +163,7 @@ class TextPositionTracker(PDFLayoutAnalyzer):
         super().__init__(rsrcmgr, pageno, laparams)
         self.textstate = None
         self.result = None
+        self.cur_item = None  # not defined in pdfminer code as it should be
 
     def begin_page(self, page, ctm):
         super().begin_page(page, ctm)
@@ -262,7 +220,17 @@ class TextPositionTracker(PDFLayoutAnalyzer):
 
 def get_page_analysis(infile, pageno, pscript5_mode):
     rman = pdfminer.pdfinterp.PDFResourceManager(caching=True)
-    dev = TextPositionTracker(rman, laparams=LAParams())
+    if pdfminer.__version__ < '20200402':
+        # Workaround for https://github.com/pdfminer/pdfminer.six/issues/395
+        disable_boxes_flow = 2
+    else:
+        disable_boxes_flow = None
+    dev = TextPositionTracker(
+        rman,
+        laparams=LAParams(
+            all_texts=True, detect_vertical=True, boxes_flow=disable_boxes_flow
+        ),
+    )
     interp = pdfminer.pdfinterp.PDFPageInterpreter(rman, dev)
 
     if pscript5_mode:

src/ocrmypdf/pluginspec.py

@@ -0,0 +1,303 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+from abc import ABC, abstractmethod, abstractstaticmethod
+from argparse import ArgumentParser, Namespace
+from collections import namedtuple
+from pathlib import Path
+from typing import TYPE_CHECKING, AbstractSet, List, Optional
+
+import pluggy
+
+from ocrmypdf.helpers import Resolution
+
+if TYPE_CHECKING:
+    from PIL import Image
+
+    from ocrmypdf._jobcontext import PageContext
+    from ocrmypdf.pdfinfo import PdfInfo
+
+hookspec = pluggy.HookspecMarker('ocrmypdf')
+
+# pylint: disable=unused-argument
+
+
+@hookspec
+def add_options(parser: ArgumentParser) -> None:
+    """Allows the plugin to add its own command line and API arguments.
+
+    OCRmyPDF converts command line arguments to API arguments, so adding
+    arguments here will cause new arguments to be processed for API calls
+    to ``ocrmypdf.ocr``, or when invoked on the command line.
+
+    Note:
+        This hook will be called from the main process, and may modify global state
+        before child worker processes are forked.
+    """
+
+
+@hookspec
+def check_options(options: Namespace) -> None:
+    """Called to ask the plugin to check all of the options.
+
+    The plugin may check if options that it added are valid.
+
+    Warnings or other messages may be passed to the user by creating a logger
+    object using ``log = logging.getLogger(__name__)`` and logging to this.
+
+    The plugin may also modify the *options*. All objects that are in options
+    must be picklable so they can be marshalled to child worker processes.
+
+    Raises:
+        ocrmypdf.exceptions.ExitCodeException: If options are not acceptable
+            and the application should terminate gracefully with an informative
+            message and error code.
+    Note:
+        This hook will be called from the main process, and may modify global state
+        before child worker processes are forked.
+	"""
+
+
+@hookspec
+def validate(pdfinfo: 'PdfInfo', options: Namespace) -> None:
+    """Called to give a plugin an opportunity to review *options* and *pdfinfo*.
+
+    *options* contains the "work order" to process a particular file. *pdfinfo*
+    contains information about the input file obtained after loading and
+    parsing. The plugin may modify the *options*. For example, you could decide
+    that a certain type of file should be treated with ``options.force_ocr = True``
+    based on information in its *pdfinfo*.
+
+    Raises:
+        ocrmypdf.exceptions.ExitCodeException: If options or pdfinfo are not acceptable
+            and the application should terminate gracefully with an informative
+            message and error code.
+    Note:
+        This hook will be called from the main process, and may modify global state
+        before child worker processes are forked.
+    """
+
+
+@hookspec(firstresult=True)
+def rasterize_pdf_page(
+    input_file: Path,
+    output_file: Path,
+    raster_device: str,
+    raster_dpi: Resolution,
+    pageno: int,
+    page_dpi: Optional[Resolution] = None,
+    rotation: Optional[int] = None,
+    filter_vector: bool = False,
+) -> Path:
+    """Rasterize one page of a PDF at resolution raster_dpi in canvas units.
+
+    The image is sized to match the integer pixels dimensions implied by
+    raster_dpi even if those numbers are noninteger. The image's DPI will
+    be overridden with the values in page_dpi.
+
+    Args:
+        input_file: The PDF to rasterize.
+        output_file: The desired name of the rasterized image.
+        raster_device: Type of image to produce at output_file
+        raster_dpi: Resolution at which to rasterize page
+        pageno: Page number to rasterize (beginning at page 1)
+        page_dpi: Resolution, overriding output image DPI
+        rotation: Cardinal angle, clockwise, to rotate page
+        filter_vector: If True, remove vector graphics objects
+    Returns:
+        Path: output_file if successful
+    Note:
+        This hook will be called from child processes. Modifying global state
+        will not affect the main process or other child processes.
+    Note:
+        This is a :ref:`firstresult hook<firstresult>`.
+    """
+
+
+@hookspec(firstresult=True)
+def filter_ocr_image(page: 'PageContext', image: 'Image') -> 'Image':
+    """Called to filter the image before it is sent to OCR.
+
+    This is the image that OCR sees, not what the user sees when they view the
+    PDF. If ``redo_ocr`` is enabled, portions of the image will be masked so
+    they are not shown to OCR. The main use of this hook is expected to be hiding
+    content from OCR.
+
+    The input image may be color, grayscale, or monochrome, and the
+    output image may differ. The pixel width and height of the
+    output image must be identical to the input image, or misalignment between
+    the OCR text layer and visual position of the text will occur. Likewise,
+    the output must be a faithful representation of the input, or alignment
+    errors may occurs.
+
+    Tesseract OCR only deals with monochrome images, and internally converts
+    non-monochrome images to OCR.
+
+    Note:
+        This hook will be called from child processes. Modifying global state
+        will not affect the main process or other child processes.
+    Note:
+        This is a :ref:`firstresult hook<firstresult>`.
+    """
+
+
+@hookspec(firstresult=True)
+def filter_page_image(page: 'PageContext', image_filename: Path) -> Path:
+    """Called to filter the whole page before it is inserted into the PDF.
+
+    A whole page image is only produced when preprocessing command line arguments
+    are issued or when ``--force-ocr`` is issued. If no whole page is image is
+    produced for a given page, this function will not be called. This is not
+    the image that will be shown to OCR.
+
+    ocrmypdf will create the PDF page based on the image format used. If you
+    convert the image to a JPEG, the output page will be created as a JPEG, etc.
+    Note that the ocrmypdf image optimization stage may ultimately chose a
+    different format.
+
+    Note:
+        This hook will be called from child processes. Modifying global state
+        will not affect the main process or other child processes.
+    Note:
+        This is a :ref:`firstresult hook<firstresult>`.
+    """
+
+
+OrientationConfidence = namedtuple('OrientationConfidence', ('angle', 'confidence'))
+"""Expresses an OCR engine's confidence in page rotation.
+
+Attributes:
+    angle (int): The clockwise angle (0, 90, 180, 270) that the page should be
+        rotated. 0 means no rotation.
+    confidence (float): How confident the OCR engine is that this the correct
+        rotation. 0 is not confident, 15 is very confident. Arbitrary units.
+"""
+
+
+class OcrEngine(ABC):
+    """A class representing an OCR engine with capabilities similar to Tesseract OCR.
+
+    This could be used to create a plugin for another OCR engine instead of
+    Tesseract OCR.
+    """
+
+    @abstractstaticmethod
+    def version() -> str:
+        """Returns the version of the OCR engine."""
+
+    @abstractstaticmethod
+    def creator_tag(options: Namespace) -> str:
+        """Returns the creator tag to identify this software's role in creating the PDF.
+
+        This tag will be inserted in the XMP metadata and DocumentInfo dictionary
+        as appropriate. Ideally you should include the name of the OCR engine and its
+        version. The text should not contain line breaks. This is to help developers
+        like yourself identify the software that produced this file.
+
+        OCRmyPDF will always prepend its name to this value.
+        """
+
+    @abstractmethod
+    def __str__(self):
+        """Returns name of OCR engine and version.
+
+        This is used when OCRmyPDF wants to mention the name of the OCR engine
+        to the user, usually in an error message.
+        """
+
+    @abstractstaticmethod
+    def languages(options: Namespace) -> AbstractSet[str]:
+        """Returns the set of all languages that are supported by the engine.
+
+        Languages are typically given in 3-letter ISO 3166-1 codes, but actually
+        can be any value understood by the OCR engine."""
+
+    @abstractstaticmethod
+    def get_orientation(input_file: Path, options: Namespace) -> OrientationConfidence:
+        """Returns the orientation of the image."""
+
+    @abstractstaticmethod
+    def generate_hocr(
+        input_file: Path, output_hocr: Path, output_text: Path, options: Namespace
+    ) -> None:
+        """Called to produce a hOCR file and sidecar text file."""
+
+    @abstractstaticmethod
+    def generate_pdf(
+        input_file: Path, output_pdf: Path, output_text: Path, options: Namespace
+    ) -> None:
+        """Called to produce a text only PDF.
+
+        Args:
+            input_file: A page image on which to perform OCR.
+            output_pdf: The expected name of the output PDF, which must be
+                a single page PDF with no visible content of any kind, sized
+                to the dimensions implied by the input_file's width, height
+                and DPI. The image will be grafted onto the input PDF page.
+        """
+
+
+@hookspec(firstresult=True)
+def get_ocr_engine() -> OcrEngine:
+    """Returns an OcrEngine to use for processing this file.
+
+    The OcrEngine may be instantiated multiple times, by both the main process
+    and child process. As such, it must be obtain store any state in ``options``
+    or some common location.
+
+    Note:
+        This is a :ref:`firstresult hook<firstresult>`.
+    """
+
+
+@hookspec(firstresult=True)
+def generate_pdfa(
+    pdf_pages: List[Path],
+    pdfmark: Path,
+    output_file: Path,
+    compression: str,
+    pdf_version: str,
+    pdfa_part: str,
+) -> Path:
+    """Generate a PDF/A.
+
+    This API strongly assumes a PDF/A generator with Ghostscript's semantics.
+
+    OCRmyPDF will modify the metadata and possibly linearize the PDF/A after it
+    is generated.
+
+    Arguments:
+        pdf_pages: A list of one or more filenames, will be merged into output_file.
+        pdfmark: A PostScript file intended for Ghostscript with details on
+            how to perform the PDF/A conversion.
+        output_file: The name of the desired output file.
+        compression: One of ``'jpeg'``, ``'lossless'``, ``''``. For ``'jpeg'``,
+            the PDF/A generator should convert all images to JPEG encoding where
+            possible. For lossless, all images should be converted to FlateEncode
+            (lossless PNG). If an empty string, the PDF generator should make its
+            own decisions about how to encode images.
+        pdf_version: The minimum PDF version that the output file should be.
+            At its own discretion, the PDF/A generator may raise the version,
+            but should not lower it.
+        pdfa_part: The desired PDF/A compliance level, such as ``'2B'``.
+
+    Returns:
+        Path: If successful, the hook should return ``output_file``.
+
+    Note:
+        This is a :ref:`firstresult hook<firstresult>`.
+    """

src/ocrmypdf/quality.py

@@ -0,0 +1,60 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Utilities to measure OCR quality"""
+
+
+import re
+from typing import Iterable
+
+
+class OcrQualityDictionary:
+    """Manages a dictionary for simple OCR quality checks."""
+
+    def __init__(self, *, wordlist: Iterable[str]):
+        """Construct a dictionary from a list of words.
+
+        Words for which capitalization is important should be capitalized in the
+        dictionary. Words that contain spaces or other punctuation will never match.
+        """
+        self.dictionary = set(wordlist)
+
+    def measure_words_matched(self, ocr_text: str) -> float:
+        """Check how many unique words in the OCR text match a dictionary.
+
+        Words with mixed capitalized are only considered a match if the test word
+        matches that capitalization.
+
+        Returns:
+            number of words that match / number
+        """
+        text = re.sub(r"[0-9_]+", ' ', ocr_text)
+        text = re.sub(r'\W+', ' ', text)
+        text_words_list = re.split(r'\s+', text)
+        text_words = {w for w in text_words_list if len(w) >= 3}
+
+        matches = 0
+        for w in text_words:
+            if w in self.dictionary or (
+                w != w.lower() and w.lower() in self.dictionary
+            ):
+                matches += 1
+        if matches > 0:
+            hit_ratio = matches / len(text_words)
+        else:
+            hit_ratio = 0.0
+        return hit_ratio

src/ocrmypdf/subprocess.py

@@ -0,0 +1,302 @@
+# © 2020 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Wrappers to manage subprocess calls"""
+
+import logging
+import os
+import re
+import shutil
+import sys
+from collections.abc import Mapping
+from contextlib import suppress
+from distutils.version import LooseVersion
+from functools import lru_cache
+from pathlib import Path
+from subprocess import PIPE, STDOUT, CalledProcessError
+from subprocess import run as subprocess_run
+
+from ocrmypdf.exceptions import MissingDependencyError
+
+log = logging.getLogger(__name__)
+
+
+def run(args, *, env=None, **kwargs):
+    """Wrapper around :py:func:`subprocess.run`
+
+    The main purpose of this wrapper is to log subprocess output in an orderly
+    fashion that indentifies the responsible subprocess. An additional
+    task is that this function goes to greater lengths to find possible Windows
+    locations of our dependencies when they are not on the system PATH.
+    """
+    if not env:
+        env = os.environ
+
+    # Search in spoof path if necessary
+    program = args[0]
+
+    if os.name == 'nt':
+        args = _fix_windows_args(program, args, env)
+
+    log.debug("Running: %s", args)
+    process_log = log.getChild('subprocess.' + os.path.basename(program))
+    if sys.version_info < (3, 7) and os.name == 'nt':
+        # Can't use close_fds=True on Windows with Python 3.6 or older
+        # https://bugs.python.org/issue19575, etc.
+        kwargs['close_fds'] = False
+
+    stderr = None
+    try:
+        proc = subprocess_run(args, env=env, **kwargs)
+    except CalledProcessError as e:
+        stderr = getattr(e, 'stderr', None)
+        raise
+    else:
+        stderr = getattr(proc, 'stderr', None)
+    finally:
+        if process_log.isEnabledFor(logging.DEBUG) and stderr:
+            with suppress(AttributeError, UnicodeDecodeError):
+                stderr = stderr.decode('utf-8', 'replace')
+            process_log.debug("stderr = %s", stderr)
+    return proc
+
+
+def _fix_windows_args(program, args, env):
+    """Adjust our desired program and command line arguments for use on Windows"""
+
+    if sys.version_info < (3, 8):
+        # bpo-33617 - Windows needs manual Path -> str conversion
+        args = [os.fspath(arg) for arg in args]
+        program = os.fspath(program)
+
+    # If we are running a .py on Windows, ensure we call it with this Python
+    # (to support test suite shims)
+    if program.lower().endswith('.py'):
+        args = [sys.executable] + args
+
+    paths = os.pathsep.join(os.get_exec_path(env))
+    if not shutil.which(args[0], path=paths):
+        # If the program we want is not on the PATH, add some interesting
+        # locations in %PROGRAMFILES% to the PATH and try again
+        shimmed_path = shim_paths_with_program_files(env)
+        new_args0 = shutil.which(args[0], path=shimmed_path)
+        if new_args0:
+            args[0] = new_args0
+    return args
+
+
+@lru_cache(maxsize=None)
+def get_version(
+    program: str, *, version_arg: str = '--version', regex=r'(\d+(\.\d+)*)', env=None
+):
+    """Get the version of the specified program
+
+    Arguments:
+        program: The program to version check.
+        version_arg: The argument needed to ask for its version, e.g. ``--version``.
+        regex: A regular expression to parse the program's output and obtain the
+            version.
+        env: Custom ``os.environ`` in which to run program.
+    """
+    args_prog = [program, version_arg]
+    try:
+        proc = run(
+            args_prog,
+            close_fds=True,
+            universal_newlines=True,
+            stdout=PIPE,
+            stderr=STDOUT,
+            check=True,
+            env=env,
+        )
+        output = proc.stdout
+    except FileNotFoundError as e:
+        raise MissingDependencyError(
+            f"Could not find program '{program}' on the PATH"
+        ) from e
+    except CalledProcessError as e:
+        if e.returncode != 0:
+            raise MissingDependencyError(
+                f"Ran program '{program}' but it exited with an error:\n{e.output}"
+            ) from e
+        raise MissingDependencyError(
+            f"Could not find program '{program}' on the PATH"
+        ) from e
+    try:
+        version = re.match(regex, output.strip()).group(1)
+    except AttributeError as e:
+        raise MissingDependencyError(
+            f"The program '{program}' did not report its version. "
+            f"Message was:\n{output}"
+        )
+
+    return version
+
+
+def shim_paths_with_program_files(env=None):
+    if not env:
+        env = os.environ
+    program_files = env.get('PROGRAMFILES', '')
+    if not program_files:
+        return env.get('PATH', '')
+
+    def path_walker():
+        for path in Path(program_files).iterdir():
+            if not path.is_dir():
+                continue
+            if path.name.lower() == 'tesseract-ocr':
+                yield path
+            elif path.name.lower() == 'gs':
+                yield from (p for p in path.glob('**/bin') if p.is_dir())
+
+    paths = sorted(
+        (p for p in path_walker()), key=lambda p: (p.name, p.parent.name), reverse=True
+    )
+    paths.extend(
+        Path(str_path)
+        for str_path in os.get_exec_path(env)
+        if Path(str_path) not in set(paths)
+    )
+    return os.pathsep.join(str(p) for p in paths)
+
+
+missing_program = '''
+The program '{program}' could not be executed or was not found on your
+system PATH.
+'''
+
+missing_optional_program = '''
+The program '{program}' could not be executed or was not found on your
+system PATH.  This program is required when you use the
+{required_for} arguments.  You could try omitting these arguments, or install
+the package.
+'''
+
+missing_recommend_program = '''
+The program '{program}' could not be executed or was not found on your
+system PATH.  This program is recommended when using the {required_for} arguments,
+but not required, so we will proceed.  For best results, install the program.
+'''
+
+old_version = '''
+OCRmyPDF requires '{program}' {need_version} or higher.  Your system appears
+to have {found_version}.  Please update this program.
+'''
+
+old_version_required_for = '''
+OCRmyPDF requires '{program}' {need_version} or higher when run with the
+{required_for} arguments.  If you omit these arguments, OCRmyPDF may be able to
+proceed.  For best results, install the program.
+'''
+
+osx_install_advice = '''
+If you have homebrew installed, try these command to install the missing
+package:
+    brew install {package}
+'''
+
+linux_install_advice = '''
+On systems with the aptitude package manager (Debian, Ubuntu), try these
+commands:
+    sudo apt-get update
+    sudo apt-get install {package}
+
+On RPM-based systems (Red Hat, Fedora), search for instructions on
+installing the RPM for {program}.
+'''
+
+windows_install_advice = '''
+If not already installed, install the Chocolatey package manager. Then use
+a command prompt to install the missing package:
+    choco install {package}
+'''
+
+
+def _get_platform():
+    if sys.platform.startswith('freebsd'):
+        return 'freebsd'
+    elif sys.platform.startswith('linux'):
+        return 'linux'
+    elif sys.platform.startswith('win'):
+        return 'windows'
+    return sys.platform
+
+
+def _error_trailer(program, package, **kwargs):
+    if isinstance(package, Mapping):
+        package = package.get(_get_platform(), program)
+
+    if _get_platform() == 'darwin':
+        log.info(osx_install_advice.format(**locals()))
+    elif _get_platform() == 'linux':
+        log.info(linux_install_advice.format(**locals()))
+    elif _get_platform() == 'windows':
+        log.info(windows_install_advice.format(**locals()))
+
+
+def _error_missing_program(program, package, required_for, recommended):
+    if recommended:
+        log.warning(missing_recommend_program.format(**locals()))
+    elif required_for:
+        log.error(missing_optional_program.format(**locals()))
+    else:
+        log.error(missing_program.format(**locals()))
+    _error_trailer(**locals())
+
+
+def _error_old_version(program, package, need_version, found_version, required_for):
+    if required_for:
+        log.error(old_version_required_for.format(**locals()))
+    else:
+        log.error(old_version.format(**locals()))
+    _error_trailer(**locals())
+
+
+def check_external_program(
+    *,
+    program,
+    package,
+    version_checker,
+    need_version,
+    required_for=None,
+    recommended=False,
+):
+    try:
+        if callable(version_checker):
+            found_version = version_checker()
+        else:
+            found_version = version_checker
+    except (CalledProcessError, FileNotFoundError, MissingDependencyError):
+        _error_missing_program(program, package, required_for, recommended)
+        if not recommended:
+            raise MissingDependencyError()
+        return
+
+    def remove_leading_v(s):
+        if s.startswith('v'):
+            return s[1:]
+        return s
+
+    found_version = remove_leading_v(found_version)
+    need_version = remove_leading_v(need_version)
+
+    if found_version and LooseVersion(found_version) < LooseVersion(need_version):
+        _error_old_version(program, package, need_version, found_version, required_for)
+        if not recommended:
+            raise MissingDependencyError()
+
+    log.debug('Found %s %s', program, found_version)

tests/cache/2400dpi/__-l__eng__000001.ocr.png__000001.text__pdf__txt/stderr.bin

@@ -1 +0,0 @@
-Tesseract Open Source OCR Engine v4.0.0 with Leptonica