Readme: Add table of contents, brew install tesseract --with-language packs

Issue #79.
User submitted PDF with ICC profile attached to the monochrome image
in the input file, which is not common but useful for PDFs that want to
define how light the paper is or how dark the black is. The code was
written to assume unusual images are full color unless it can prove
otherwise. Handle this simple case. Other ICC cases should be tested.

README.rst

@@ -8,7 +8,7 @@ Main features
 -------------
 
 -  Generates a searchable
-   `PDF/A <https://en.wikipedia.org/?title=PDF/A>`__ file from a regular PDF
+   `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 rendering vector information
@@ -18,11 +18,11 @@ Main features
 -  Provides debug mode to enable easy verification of the OCR results
 -  Processes pages in parallel when more than one CPU core is
    available
--  Uses `Tesseract OCR <https://github.com/tesseract-ocr/tesseract>`__ engine
--  Supports the `39 languages <https://code.google.com/p/tesseract-ocr/downloads/list>`__ recognized by Tesseract
+-  Uses `Tesseract OCR <https://github.com/tesseract-ocr/tesseract>`_ engine
+-  Supports the `39 languages <https://code.google.com/p/tesseract-ocr/downloads/list>`_ recognized by Tesseract
 -  Battle-tested on thousands of PDFs, a test suite and continuous integration
 
-For details: please consult the `release notes <RELEASE_NOTES.rst>`__.
+For details: please consult the `release notes <RELEASE_NOTES.rst>`_.
 
 Motivation
 ----------
@@ -31,9 +31,9 @@ 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.
 
 -  Either they produced PDF files with misplaced text under the image (making copy/paste impossible) 
--  Or they did not display correctly some escaped HTML characters located in the hOCR file produced by the OCR engine 
+-  Or they did not handle accents and multilingual characters
 -  Or they changed the resolution of the embedded images
--  Or they generated PDF files having a ridiculous big size
+-  Or they generated ridiculously large PDF files
 -  Or they crashed when trying to OCR some of my PDF files
 -  Or they did not produce valid PDF files (even though they were readable with my current PDF reader)
 -  On top of that none of them produced PDF/A files (format dedicated for long time storage)
@@ -46,28 +46,45 @@ Installation
 
 Download OCRmyPDF here: https://github.com/jbarlow83/OCRmyPDF/releases
 
-You can install it to a Python virtual environment or system-wide. 
+These steps describe how to install OCRmyPDF on your system.
 
-Debian and Ubuntu
-~~~~~~~~~~~~~~~~~
+- `Installing on Debian and Ubuntu`_ (Debian stretch and Ubuntu 16.10 or later)
+- `Installing the Docker image`_
+- `Installing on Mac OS X`_
+- `Installing on Ubuntu 14.04 LTS`_
+- Installing and running on `Windows`_ using the Docker image
+
+If you prefer to install from source or install OCRmyPDF to a Python virtual environment, see steps for `Installing HEAD revision from sources`_.
+
+.. _Windows: `Installing on Windows`_
+
+
+Installing on Debian and Ubuntu
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Users of Debian 9 or later or Ubuntu 16.10 or later may simply
 ``apt-get install ocrmypdf``.
 
+.. _Docker:
+
 Installing the Docker image
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 For many users, installing the Docker image will be easier than installing all of OCRmyPDF's dependencies. For Windows, it is the only option.
 
-If you have `Docker <https://docs.docker.com/>`__ installed on your system, you can install
+If you have `Docker <https://docs.docker.com/>`_ installed on your system, you can install
 a Docker image of the latest release.
 
 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::
+successfully, your system is ready to download and execute the image:
+
+.. code-block:: bash
 
    docker run hello-world
    
-OCRmyPDF will use all available CPU cores.  By default, the VirtualBox machine instance on Windows and OS X 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 OS X 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"
@@ -76,29 +93,41 @@ OCRmyPDF will use all available CPU cores.  By default, the VirtualBox machine i
    eval $(docker-machine env "yourVM")
 
 Assuming you have a Docker engine running somewhere, you can run these commands to download
-the image::
+the image:
+
+.. code-block:: bash
 
    docker pull jbarlow83/ocrmypdf
 
-Then tag it to give a more convenient name, just ocrmypdf::
+Then tag it to give a more convenient name, just ocrmypdf:
+
+.. code-block:: bash
 
    docker tag jbarlow83/ocrmypdf ocrmypdf
 
-This image contains language packs for English, French, Spanish and German. The alternative "polyglot" image provides `all available language packs <https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#languages>`__::
+This image contains language packs for English, French, Spanish and German. The alternative "polyglot" image provides `all available language packs <https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#languages>`_:
+
+.. code-block:: bash
 
    # Alternative step: If you need all language packs
    docker pull jbarlow83/ocrmypdf-polyglot
    docker tag jbarlow83/ocrmypdf-polyglot ocrmypdf
 
-You can then run ocrmypdf using the command::
+You can then run ocrmypdf using the command:
+
+.. code-block:: bash
 
    docker run ocrmypdf --help
   
-To execute the OCRmyPDF on a local file, you must `provide a writable volume to the Docker image <https://docs.docker.com/userguide/dockervolumes/>`__, such as this in this template::
+To execute the OCRmyPDF on a local file, you must `provide a writable volume to the Docker image <https://docs.docker.com/userguide/dockervolumes/>`_, such as this in this template:
+
+.. code-block:: bash
 
    docker run -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``:: 
+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 -v "$(pwd):/home/docker"   ocrmypdf --skip-text test.pdf output.pdf
 
@@ -110,32 +139,51 @@ Installing on Mac OS X
 
 These instructions probably work on all Mac OS X versions later than 10.7 (Lion). OCRmyPDF is known to work on Yosemite and El Capitan, and regularly tested on El Capitan.
 
-If it's not already present, `install Homebrew <http://brew.sh/>`__.
+If it's not already present, `install Homebrew <http://brew.sh/>`_.
 
-Update Homebrew::
+Update Homebrew:
+
+.. code-block:: bash
 
    brew update
    
-Install or upgrade the required Homebrew packages, if any are missing::
+Install or upgrade the required Homebrew packages, if any are missing:
 
-   brew install libpng openjpeg jbig2dec     # image libraries
+.. code-block:: bash
+
+   brew install libpng openjpeg jbig2dec libtiff     # image libraries
    brew install qpdf
    brew install ghostscript
    brew install python3
    brew install libxml2 libffi leptonica
-   brew install unpaper    # optional
-   brew install tesseract
+   brew install unpaper   # optional
    
-Update the homebrew pip and install Pillow::
+Install the required Tesseract OCR engine with the language packs you plan to use:
+   
+.. code-block:: bash
+
+   brew install tesseract                       # Option 1: for English, French, German, Spanish
+   
+.. code-block:: bash
+   
+   brew install tesseract --with-all-languages  # Option 2: for all language packs 
+   
+Update the homebrew pip and install Pillow:
+
+.. code-block:: bash
 
    pip3 install --upgrade pip
    pip3 install --upgrade pillow
 
-You can then install OCRmyPDF from PyPI::
+You can then install OCRmyPDF from PyPI:
+
+.. code-block:: bash
 
    pip3 install ocrmypdf
 
-The command line program should now be available::
+The command line program should now be available:
+
+.. code-block:: bash
 
    ocrmypdf --help
 
@@ -144,12 +192,16 @@ Installing on Ubuntu 14.04 LTS
 
 Installing on Ubuntu 14.04 LTS (trusty) is more difficult than other options, because of certain bugs in Python package installation.
 
-Update apt-get::
+Update apt-get:
+
+.. code-block:: bash
 
    sudo apt-get update
    sudo apt-get upgrade
    
-Install system dependencies::
+Install system dependencies:
+
+.. code-block:: bash
 
    sudo apt-get install \
       zlib1g-dev \
@@ -165,13 +217,17 @@ Install system dependencies::
       python3-reportlab
 
 If you wish install OCRmyPDF to the system Python, then install as follows (note this installs new packages
-into your system Python, which could interfere with other programs)::
+into your system Python, which could interfere with other programs):
+
+.. code-block:: bash
 
    sudo pip3 install ocrmypdf
    
 If you wish to install OCRmyPDF to a virtual environment to isolate system Python from modified, you can
 follow these steps.  This includes a workaround `for a known, unresolved issue in Ubuntu 14.04's ensurepip
-package <http://www.thefourtheye.in/2014/12/Python-venv-problem-with-ensurepip-in-Ubuntu.html>`__::
+package <http://www.thefourtheye.in/2014/12/Python-venv-problem-with-ensurepip-in-Ubuntu.html>`_:
+
+.. code-block:: bash
 
    sudo apt-get install python3-venv
    python3 -m venv venv-ocrmypdf --without-pip
@@ -182,19 +238,23 @@ package <http://www.thefourtheye.in/2014/12/Python-venv-problem-with-ensurepip-i
    source venv-ocrmypdf/bin/activate
    pip install ocrmypdf
 
-Ubuntu 14.04 only installs ``unpaper`` version 0.4.2, which is not supported by OCRmyPDF because it is produces invalid output. This program is an optional dependency, and provides page deskewing and cleaning. See `Dockerfile <Dockerfile>`__ for an example of how to building unpaper 6.1 from source. If you choose to install unpaper later, OCRmyPDF will use the foremost version on the system PATH.
+Ubuntu 14.04 only installs ``unpaper`` version 0.4.2, which is not supported by OCRmyPDF because it is produces invalid output. This program is an optional dependency, and provides page deskewing and cleaning. See `Dockerfile <Dockerfile>`_ for an example of how to building unpaper 6.1 from source. If you choose to install unpaper later, OCRmyPDF will use the foremost version on the system PATH.
 
 Installing on Windows
 ~~~~~~~~~~~~~~~~~~~~~
 
-Direct installation on Windows is not possible.  Install the Docker container as described above.  Ensure that your command prompt can run the docker "hello world" container.
+Direct installation on Windows is not possible.  Install the _`Docker` container as described above.  Ensure that your command prompt can run the docker "hello world" container.
 
-The command line syntax to run ocrmypdf from a command prompt will resemble::
+Running on Windows
+~~~~~~~~~~~~~~~~~~
+
+The command line syntax to run ocrmypdf from a command prompt will resemble:
+
+.. code-block:: bat
 
    docker run -v /c/Users/sampleuser:/home/docker ocrmypdf --skip-text test.pdf output.pdf
 
-where /c/Users/sampleuser is a Unix representation of the Windows path C:\Users\sampleuser, assuming a user named "sampleuser" is running ocrmypdf on a file in their home directory, and the files "test.pdf" and "output.pdf" are in the sampleuser folder. The Windows user must have read and write permissions.
-
+where /c/Users/sampleuser is a Unix representation of the Windows path C:\\Users\\sampleuser, assuming a user named "sampleuser" is running ocrmypdf on a file in their home directory, and the files "test.pdf" and "output.pdf" are in the sampleuser folder. The Windows user must have read and write permissions.
       
 Installing HEAD revision from sources
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -202,21 +262,29 @@ Installing HEAD revision from sources
 If you have ``git`` and ``python3.4`` or ``python3.5`` installed, you can install from source. When the ``pip`` installer runs,
 it will alert you if dependencies are missing.
 
-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
    
 On certain Linux distributions such as Ubuntu, you may need to use 
-run the install command as superuser::
+run the install command as superuser:
+
+.. code-block:: bash
 
    sudo pip3 install [-e] git+https://github.com/jbarlow83/OCRmyPDF.git
    
 Note that this will alter your system's Python distribution. If you prefer 
-to not install as superuser, you can install the package in a Python virtual environment::
+to not install as superuser, you can install the package in a Python virtual environment:
+
+.. code-block:: bash
 
    git clone -b master https://github.com/jbarlow83/OCRmyPDF.git
    pyvenv venv
@@ -227,7 +295,9 @@ to not install as superuser, you can install the package in a Python virtual env
 However, ``ocrmypdf`` will only be accessible on the system PATH after
 you activate the virtual environment.
 
-To run the program::
+To run the program:
+
+.. code-block:: bash
    
    ocrmypdf --help
 
@@ -240,10 +310,15 @@ Languages
 ---------
 
 OCRmyPDF uses Tesseract for OCR, and relies on its language packs. For Linux users,
-you can often find packages that provide language packs::
+you can often find packages that provide language packs:
+
+.. code-block:: bash
+
+   # Display a list of all Tesseract language packs
+   apt-cache search tesseract-ocr
 
    # Debian/Ubuntu users
-   sudo apt-get install tesseract-ocr-chi-sim
+   sudo apt-get install tesseract-ocr-chi-sim  # Example: Install Chinese Simplified language back
    
 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.
@@ -251,9 +326,17 @@ languages can be requested.
 Support
 -------
 
-In case you detect an issue, please:
+Once ocrmypdf is installed, the built-in help which explains the command syntax and options can be accessed via:
 
--  Check if your issue is already known
+.. code-block:: bash
+
+   ocrmypdf --help
+
+The `Wiki <https://github.com/jbarlow83/OCRmyPDF/wiki>`_ page also contains some tips and suggests.
+
+If you detect an issue, please:
+
+-  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
@@ -265,11 +348,11 @@ In case you detect an issue, please:
 Press & Media
 -------------
 
--  `c't 1-2014, page 59 <http://heise.de/-2279695>`__:
+-  `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>`__
+   OCRmyPDF <http://heise.de/-2356670>`_
 
 Disclaimer
 ----------

RELEASE_NOTES.rst

@@ -6,6 +6,12 @@ Please always read this file before installing the package
 Download software here: https://github.com/jbarlow83/OCRmyPDF/tags
 
 
+v4.1.4:
+=======
+
+-  Bug fix: monochrome images with an ICC profile attached were incorrectly converted to full color images if lossless reconstruction was not possible due to other settings; consequence was increased file size for these images
+
+
 v4.1.3:
 =======
 

ocrmypdf/pageinfo.py

@@ -230,6 +230,14 @@ def _find_page_regular_images(page, pageinfo, contentsinfo):
             image['color'] = 'jpx' if image['enc'] == 'jpx' else '?'
 
         image['comp'] = FRIENDLY_COMP.get(image['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 image['comp'] == '?' and image['enc'] in ('ccitt', 'jbig2'):
+            image['comp'] = FRIENDLY_COMP['gray']
+
         image['dpi_w'] = image['dpi_h'] = 0
 
         for raster in contentsinfo.raster_settings:

tests/resources/README.rst

@@ -47,12 +47,13 @@ These test resources are assemblies from other previously mentioned files, relea
 
 - cardinal.pdf (four cardinal directions, rotated copies of LinnSequencer.jpg)
 - ccitt.pdf (LinnSequencer.jpg, converted to CCITT encoding)
+- encrypted_algo4.pdf (congress.jpg, encrypted with algorithm 4 - not supported by PyPDF2)
 - graph_ocred.pdf (from graph.pdf)
 - jbig2.pdf (congress.jpg, converted to JBIG2 encoding)
 - multipage.pdf (from several other files)
 - palette.pdf (congress.jpg, converted to a 256-color palette)
 - skew.pdf (from c02-22.pdf)
-- skew-encrypted.pdf (skew.pdf with encrypted applied)
+- skew-encrypted.pdf (skew.pdf with encryption - access supported by PyPDF2)
 
 
 .. _`Wikimedia: LinnSequencer`: https://upload.wikimedia.org/wikipedia/en/b/b7/LinnSequencer_hardware_MIDI_sequencer_brochure_page_2_300dpi.jpg
@@ -63,4 +64,4 @@ These test resources are assemblies from other previously mentioned files, relea
 
 .. _`Wikimedia: Pandas text analysis.png`: https://en.wikipedia.org/wiki/File:Pandas_text_analysis.png
 
-.. _`Wikimedia: JPEG2000 Lichtenstein`: https://en.wikipedia.org/wiki/JPEG_2000#/media/File:Jpeg2000_2-level_wavelet_transform-lichtenstein.png
+.. _`Wikimedia: JPEG2000 Lichtenstein`: https://en.wikipedia.org/wiki/JPEG_2000#/media/File:Jpeg2000_2-level_wavelet_transform-lichtenstein.png