OCRmyPDF/ocrmypdf/pipeline.py

#!/usr/bin/env python3
# © 2016 James R. Barlow: github.com/jbarlow83

from contextlib import suppress
from tempfile import mkdtemp
from functools import partial
import sys
import os
import re
import shutil
import warnings
import multiprocessing
import atexit
import textwrap
import img2pdf
import logging
import argparse

import PyPDF2 as pypdf
from PIL import Image

from ruffus import formatter, regex, Pipeline, suffix

from .hocrtransform import HocrTransform
from .pageinfo import pdf_get_all_pageinfo
from .pdfa import generate_pdfa_def, file_claims_pdfa
from . import ghostscript
from . import tesseract
from . import qpdf
from . import leptonica
from . import ExitCode, page_number, is_iterable_notstr, PROGRAM_NAME, \
    VERSION


VECTOR_PAGE_DPI = 400

# -------------
# Pipeline state manager

class JobContext:
    """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.

    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 __init__(self):
        self.pdfinfo = []

    def get_pdfinfo(self):
        "What we know about the input PDF"
        return self.pdfinfo

    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


from multiprocessing.managers import BaseManager
class JobContextManager(BaseManager):
    pass



def re_symlink(input_file, soft_link_name, log):
    """
    Helper function: relinks soft symbolic link if necessary
    """

    # Guard against soft linking to oneself
    if input_file == soft_link_name:
        log.debug("Warning: No symbolic link made. You are using " +
                  "the original data directory as the working directory.")
        return

    # Soft link already exists: delete for relink?
    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)
        try:
            os.unlink(soft_link_name)
        except:
            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)

    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 cleanup_working_files(work_folder, options):
    if options.keep_temporary_files:
        print("Temporary working files saved at:\n{0}".format(work_folder),
              file=sys.stderr)
    else:
        with suppress(FileNotFoundError):
            shutil.rmtree(work_folder)


#
# The Pipeline
#


def triage_image_file(input_file, output_file, log, options):
    try:
        log.info("Input file is not a PDF, checking if it is an image...")
        im = Image.open(input_file)
    except EnvironmentError as e:
        msg = str(e)

        # Recover the original filename
        realpath = ''
        if os.path.islink(input_file):
            realpath = os.path.realpath(input_file)
        elif os.path.isfile(input_file):
            realpath = '<stdin>'
        msg = msg.replace(input_file, realpath)
        log.error(msg)
        sys.exit(ExitCode.input_file)
        return
    else:
        log.info("Input file is an image")

        if 'dpi' in im.info:
            if im.info['dpi'] <= (96, 96) and not options.image_dpi:
                log.info("Image size: (%d, %d)" % im.size)
                log.info("Image resolution: (%d, %d)" % im.info['dpi'])
                log.error(
                    "Input file is an image, but the resolution (DPI) is "
                    "not credible.  Estimate the resolution at which the "
                    "image was scanned and specify it using --image-dpi.")
                sys.exit(ExitCode.input_file)
        elif not options.image_dpi:
            log.info("Image size: (%d, %d)" % im.size)
            log.error(
                "Input file is an image, but has no resolution (DPI) "
                "in its metadata.  Estimate the resolution at which "
                "image was scanned and specify it using --image-dpi.")
            sys.exit(ExitCode.input_file)

        if 'iccprofile' not in im.info:
            if im.mode == 'RGB':
                log.info('Input image has no ICC profile, assuming sRGB')
            elif im.mode == 'CMYK':
                log.info('Input CMYK image has no ICC profile, not usable')
                sys.exit(ExitCode.input_file)
        im.close()

    try:
        log.info("Image seems valid. Try converting to PDF...")
        layout_fun = img2pdf.default_layout_fun
        if options.image_dpi:
            layout_fun = img2pdf.get_fixed_dpi_layout_fun(
                (options.image_dpi, options.image_dpi))
        with open(output_file, 'wb') as outf:
            img2pdf.convert(
                input_file,
                layout_fun=layout_fun,
                with_pdfrw=False,
                outputstream=outf)
        log.info("Successfully converted to PDF, processing...")
    except img2pdf.ImageOpenError as e:
        log.error(e)
        sys.exit(ExitCode.input_file)


def triage(
        input_file,
        output_file,
        log,
        context):

    try:
        with open(input_file, 'rb') as f:
            signature = f.read(4)
            if signature == b'%PDF':
                re_symlink(input_file, output_file, log)
                return
    except EnvironmentError as e:
        log.error(e)
        sys.exit(ExitCode.input_file)

    options = context.get_options()
    triage_image_file(input_file, output_file, log, options)


def repair_pdf(
        input_file,
        output_file,
        log,
        context):

    qpdf.repair(input_file, output_file, log)
    pdfinfo = pdf_get_all_pageinfo(output_file)
    context.set_pdfinfo(pdfinfo)
    log.debug(pdfinfo)


def get_pageinfo(input_file, context):
    pageno = int(os.path.basename(input_file)[0:6]) - 1
    pageinfo = context.get_pdfinfo()[pageno].copy()
    return pageinfo


def get_page_dpi(pageinfo, options):
    "Get the DPI when nonsquare DPI is tolerable"
    xres = max(pageinfo.get('xres', VECTOR_PAGE_DPI), options.oversample or 0)
    yres = max(pageinfo.get('yres', VECTOR_PAGE_DPI), options.oversample or 0)
    return (float(xres), float(yres))


def get_page_square_dpi(pageinfo, options):
    "Get the DPI when we require xres == yres"
    return float(max(
        pageinfo.get('xres', VECTOR_PAGE_DPI),
        pageinfo.get('yres', VECTOR_PAGE_DPI),
        options.oversample or 0))


def is_ocr_required(pageinfo, log, options):
    page = pageinfo['pageno'] + 1
    ocr_required = True
    if not pageinfo['images']:
        if options.force_ocr and options.oversample:
            # The user really wants to reprocess this file
            log.info(
                "{0:4d}: page has no images - "
                "rasterizing at {1} DPI because "
                "--force-ocr --oversample was specified".format(
                    page, options.oversample))
        elif options.force_ocr:
            # Warn the user they might not want to do this
            log.warning(
                "{0:4d}: page has no images - "
                "all vector content will be "
                "rasterized at {1} DPI, losing some resolution and likely "
                "increasing file size. Use --oversample to adjust the "
                "DPI.".format(page, VECTOR_PAGE_DPI))
        else:
            log.info(
                "{0:4d}: page has no images - "
                "skipping all processing on this page".format(page))
            ocr_required = False

    elif pageinfo['has_text']:
        msg = "{0:4d}: page already has text! – {1}"

        if not options.force_ocr and not options.skip_text:
            log.error(msg.format(page,
                                 "aborting (use --force-ocr to force OCR)"))
            sys.exit(ExitCode.already_done_ocr)
        elif options.force_ocr:
            log.info(msg.format(page,
                                "rasterizing text and running OCR anyway"))
            ocr_required = True
        elif options.skip_text:
            log.info(msg.format(page,
                                "skipping all processing on this page"))
            ocr_required = False

    if ocr_required and options.skip_big:
        pixel_count = pageinfo['width_pixels'] * pageinfo['height_pixels']
        if pixel_count > (options.skip_big * 1000000):
            ocr_required = False
            log.warning(
                "{0:4d}: page too big, skipping OCR "
                "({1:.1f} MPixels > {2:.1f} MPixels --skip-big)".format(
                    page, pixel_count / 1000000, options.skip_big))
    return ocr_required


def split_pages(
        input_files,
        output_files,
        log,
        context):

    options = context.get_options()
    work_folder = context.get_work_folder()

    if is_iterable_notstr(input_files):
        input_file = input_files[0]
    else:
        input_file = input_files

    for oo in output_files:
        with suppress(FileNotFoundError):
            os.unlink(oo)

    # If no files were repaired the input will be empty
    if not input_file:
        log.error("{0}: file not found or invalid argument".format(
                options.input_file))
        sys.exit(ExitCode.input_file)

    npages = qpdf.get_npages(input_file, log)
    qpdf.split_pages(input_file, work_folder, npages)

    from glob import glob
    for filename in glob(os.path.join(work_folder, '*.page.pdf')):
        pageinfo = get_pageinfo(filename, context)

        alt_suffix = \
            '.ocr.page.pdf' if is_ocr_required(pageinfo, log, options) \
            else '.skip.page.pdf'
        re_symlink(
            filename,
            os.path.join(
                work_folder,
                os.path.basename(filename)[0:6] + alt_suffix),
            log)


def rasterize_preview(
        input_file,
        output_file,
        log,
        context):
    ghostscript.rasterize_pdf(
        input_file=input_file,
        output_file=output_file,
        xres=200,
        yres=200,
        raster_device='jpeggray',
        log=log)


def orient_page(
        infiles,
        output_file,
        log,
        context):

    options = context.get_options()
    page_pdf = next(ii for ii in infiles if ii.endswith('.page.pdf'))

    if not options.rotate_pages:
        re_symlink(page_pdf, output_file, log)
        return
    preview = next(ii for ii in infiles if ii.endswith('.preview.jpg'))

    orient_conf = tesseract.get_orientation(
        preview,
        language=options.language,
        timeout=options.tesseract_timeout,
        log=log)

    direction = {
        0: '⇧',
        90: '⇨',
        180: '⇩',
        270: '⇦'
    }

    apply_correction = False
    description = ''
    if orient_conf.confidence >= options.rotate_pages_threshold:
        if orient_conf.angle != 0:
            apply_correction = True
            description = ' - will rotate'
        else:
            description = ' - rotation appears correct'
    else:
        if orient_conf.angle != 0:
            description = ' - confidence too low to rotate'
        else:
            description = ' - no change'

    log.info(
        '{0:4d}: page is facing {1}, confidence {2:.2f}{3}'.format(
            page_number(preview),
            direction.get(orient_conf.angle, '?'),
            orient_conf.confidence,
            description)
    )

    if not apply_correction:
        re_symlink(page_pdf, output_file, log)
    else:
        writer = pypdf.PdfFileWriter()
        reader = pypdf.PdfFileReader(page_pdf)
        page = reader.pages[0]

        # angle is a clockwise angle, so rotating ccw will correct the error
        rotated_page = page.rotateCounterClockwise(orient_conf.angle)
        writer.addPage(rotated_page)
        with open(output_file, 'wb') as out:
            writer.write(out)

        pageno = int(os.path.basename(page_pdf)[0:6]) - 1
        pdfinfo = context.get_pdfinfo()
        pdfinfo[pageno]['rotated'] = orient_conf.angle
        context.set_pdfinfo(pdfinfo)


def rasterize_with_ghostscript(
        input_file,
        output_file,
        log,
        context):
    options = context.get_options()
    pageinfo = get_pageinfo(input_file, context)

    device = 'png16m'  # 24-bit
    if all(image['comp'] == 1 for image in pageinfo['images']):
        if all(image['bpc'] == 1 for image in pageinfo['images']):
            device = 'pngmono'
        elif all(image['bpc'] > 1 and image['color'] == 'index'
                 for image in pageinfo['images']):
            device = 'png256'
        elif all(image['bpc'] > 1 and image['color'] == 'gray'
                 for image in pageinfo['images']):
            device = 'pnggray'

    log.debug("Rasterize {0} with {1}".format(
              os.path.basename(input_file), device))

    # Produce the page image with square resolution or else deskew and OCR
    # will not work properly
    dpi = get_page_square_dpi(pageinfo, options)
    ghostscript.rasterize_pdf(
        input_file, output_file, xres=dpi, yres=dpi, raster_device=device,
        log=log)


def preprocess_remove_background(
        input_file,
        output_file,
        log,
        context):
    options = context.get_options()
    if not options.remove_background:
        re_symlink(input_file, output_file, log)
        return

    pageinfo = get_pageinfo(input_file, context)

    if any(image['bpc'] > 1 for image in pageinfo['images']):
        leptonica.remove_background(input_file, output_file)
    else:
        log.info("{0:4d}: background removal skipped on mono page".format(
            pageinfo['pageno']))
        re_symlink(input_file, output_file, log)


def preprocess_deskew(
        input_file,
        output_file,
        log,
        context):
    options = context.get_options()
    if not options.deskew:
        re_symlink(input_file, output_file, log)
        return

    pageinfo = get_pageinfo(input_file, context)
    dpi = get_page_square_dpi(pageinfo, options)

    leptonica.deskew(input_file, output_file, dpi)


def preprocess_clean(
        input_file,
        output_file,
        log,
        context):
    options = context.get_options()
    if not options.clean:
        re_symlink(input_file, output_file, log)
        return

    from . import unpaper
    pageinfo = get_pageinfo(input_file, context)
    dpi = get_page_square_dpi(pageinfo, options)

    unpaper.clean(input_file, output_file, dpi, log)


def ocr_tesseract_hocr(
        input_file,
        output_file,
        log,
        context):
    options = context.get_options()
    tesseract.generate_hocr(
        input_file=input_file,
        output_hocr=output_file,
        language=options.language,
        tessconfig=options.tesseract_config,
        timeout=options.tesseract_timeout,
        pageinfo_getter=partial(get_pageinfo, input_file, context),
        pagesegmode=options.tesseract_pagesegmode,
        log=log
        )


def select_image_for_pdf(
        infiles,
        output_file,
        log,
        context):
    options = context.get_options()
    if options.clean_final:
        image_suffix = '.pp-clean.png'
    elif options.deskew:
        image_suffix = '.pp-deskew.png'
    elif options.remove_background:
        image_suffix = '.pp-background.png'
    else:
        image_suffix = '.page.png'
    image = next(ii for ii in infiles if ii.endswith(image_suffix))

    pageinfo = get_pageinfo(image, context)
    if all(orig_image['enc'] == 'jpeg' for orig_image in pageinfo['images']):
        # If all images were JPEGs originally, produce a JPEG as output
        im = Image.open(image)

        # At this point the image should be a .png, but deskew, unpaper might
        # have removed the DPI information. In this case, fall back to square
        # DPI used to rasterize. When the preview image was rasterized, it
        # was also converted to square resolution, which is what we want to
        # give tesseract, so keep it square.
        fallback_dpi = get_page_square_dpi(pageinfo, options)
        dpi = im.info.get('dpi', (fallback_dpi, fallback_dpi))

        # Pillow requires integer DPI
        dpi = round(dpi[0]), round(dpi[1])
        im.save(output_file, format='JPEG', dpi=dpi)
    else:
        re_symlink(image, output_file, log)


def select_image_layer(
        infiles,
        output_file,
        log,
        context):
    options = context.get_options()
    page_pdf = next(ii for ii in infiles if ii.endswith('.ocr.oriented.pdf'))
    image = next(ii for ii in infiles if ii.endswith('.image'))

    if options.lossless_reconstruction:
        log.debug("{:4d}: page eligible for lossless reconstruction".format(
            page_number(page_pdf)))
        re_symlink(page_pdf, output_file, log)
    else:
        pageinfo = get_pageinfo(image, context)
        dpi = get_page_dpi(pageinfo, options)
        dpi = float(dpi[0]), float(dpi[1])
        layout_fun = img2pdf.get_fixed_dpi_layout_fun(dpi)

        with open(image, 'rb') as imfile, \
                open(output_file, 'wb') as pdf:
            rawdata = imfile.read()
            log.debug('{:4d}: convert'.format(page_number(page_pdf)))
            img2pdf.convert(
                rawdata, with_pdfrw=False,
                layout_fun=layout_fun, outputstream=pdf)
            log.debug('{:4d}: convert done'.format(page_number(page_pdf)))


def render_hocr_page(
        input_file,
        output_file,
        log,
        context):
    options = context.get_options()
    hocr = input_file
    pageinfo = get_pageinfo(hocr, context)
    dpi = get_page_square_dpi(pageinfo, options)

    hocrtransform = HocrTransform(hocr, dpi)
    hocrtransform.to_pdf(output_file, imageFileName=None,
                         showBoundingboxes=False, invisibleText=True)


def render_hocr_debug_page(
        infiles,
        output_file,
        log,
        context):
    options = context.get_options()
    hocr = next(ii for ii in infiles if ii.endswith('.hocr'))
    image = next(ii for ii in infiles if ii.endswith('.image'))

    pageinfo = get_pageinfo(image, context)
    dpi = get_page_square_dpi(pageinfo, options)

    hocrtransform = HocrTransform(hocr, dpi)
    hocrtransform.to_pdf(output_file, imageFileName=None,
                         showBoundingboxes=True, invisibleText=False)


class PdfMergeFailedError(Exception):
    pass


def add_text_layer(
        infiles,
        output_file,
        log,
        context):
    text = next(ii for ii in infiles if ii.endswith('.hocr.pdf'))
    image = next(ii for ii in infiles if ii.endswith('.image-layer.pdf'))

    pdf_text = pypdf.PdfFileReader(open(text, "rb"))
    pdf_image = pypdf.PdfFileReader(open(image, "rb"))

    page_text = pdf_text.getPage(0)

    # The text page always will be oriented up by this stage
    # but if lossless_reconstruction, pdf_image may have a rotation applied
    # We have to eliminate the /Rotate tag (because it applies to the whole
    # page) and rotate the image layer to match the text page
    # Also, pdf_image may not have its mediabox nailed to (0, 0), so may need
    # translation
    page_image = pdf_image.getPage(0)
    try:
        # pypdf DictionaryObject.get() does not resolve indirect objects but
        # __getitem__ does
        rotation = page_image['/Rotate']
    except KeyError:
        rotation = 0

    # /Rotate is a clockwise rotation: 90 means page facing "east"
    # The negative of this value is the angle that eliminates that rotation
    rotation = -rotation % 360

    x1 = page_image.mediaBox.getLowerLeft_x()
    x2 = page_image.mediaBox.getUpperRight_x()
    y1 = page_image.mediaBox.getLowerLeft_y()
    y2 = page_image.mediaBox.getUpperRight_y()

    # Rotation occurs about the page's (0, 0). Most pages will have the media
    # box at (0, 0) with all content in the first quadrant but some cropped
    # files may have an offset mediabox. We translate the page so that its
    # bottom left corner after rotation is pinned to (0, 0) with the image
    # in the first quadrant.
    if rotation == 0:
        tx, ty = -x1, -y1
    elif rotation == 90:
        tx, ty = y2, -x1
    elif rotation == 180:
        tx, ty = x2, y2
    elif rotation == 270:
        tx, ty = -y1, x2
    else:
        pass

    if rotation != 0:
        log.info("{0:4d}: rotating image layer {1} degrees".format(
            page_number(image), rotation, tx, ty))

    try:
        page_text.mergeRotatedScaledTranslatedPage(
            page_image, rotation, 1.0, tx, ty, expand=False)
    except (AttributeError, ValueError) as e:
        if 'writeToStream' in str(e) or 'invalid literal' in str(e):
            raise PdfMergeFailedError() from e

    pdf_output = pypdf.PdfFileWriter()
    pdf_output.addPage(page_text)

    with open(output_file, "wb") as out:
        pdf_output.write(out)


def tesseract_ocr_and_render_pdf(
        input_files,
        output_file,
        log,
        context):
    options = context.get_options()
    input_image = next((ii for ii in input_files if ii.endswith('.image')), '')
    input_pdf = next((ii for ii in input_files if ii.endswith('.pdf')))
    if not input_image:
        # Skipping this page
        re_symlink(input_pdf, output_file, log)
        return

    tesseract.generate_pdf(
        input_image=input_image,
        skip_pdf=input_pdf,
        output_pdf=output_file,
        language=options.language,
        tessconfig=options.tesseract_config,
        timeout=options.tesseract_timeout,
        pagesegmode=options.tesseract_pagesegmode,
        log=log)


def get_pdfmark(base_pdf, options):
    def from_document_info(key):
        # pdf.documentInfo.get() DOES NOT behave as expected for a dict-like
        # object, so call with precautions.  TypeError may occur if the PDF
        # is missing the optional document info section.
        try:
            s = base_pdf.documentInfo[key]
            return str(s)
        except (KeyError, TypeError):
            return ''

    pdfmark = {
        '/Title': from_document_info('/Title'),
        '/Author': from_document_info('/Author'),
        '/Keywords': from_document_info('/Keywords'),
        '/Subject': from_document_info('/Subject'),
    }
    if options.title:
        pdfmark['/Title'] = options.title
    if options.author:
        pdfmark['/Author'] = options.author
    if options.keywords:
        pdfmark['/Keywords'] = options.keywords
    if options.subject:
        pdfmark['/Subject'] = options.subject

    pdfmark['/Creator'] = '{0} {1} / Tesseract OCR{2} {3}'.format(
            PROGRAM_NAME, VERSION,
            '+PDF' if options.pdf_renderer == 'tesseract' else '',
            tesseract.version())
    return pdfmark


def generate_postscript_stub(
        input_file,
        output_file,
        log,
        context):
    options = context.get_options()
    pdf = pypdf.PdfFileReader(input_file)
    pdfmark = get_pdfmark(pdf, options)
    generate_pdfa_def(output_file, pdfmark)


def skip_page(
        input_file,
        output_file,
        log):
    # The purpose of this step is its filter to forward only the skipped
    # files (.skip.oriented.pdf) while disregarding the processed ones
    # (.ocr.oriented.pdf).  Alternative would be for merge_pages to filter
    # pages itself if it gets multiple copies of a page.
    re_symlink(input_file, output_file, log)


def merge_pages_ghostscript(
        input_files,
        output_file,
        log,
        context):
    options = context.get_options()
    def input_file_order(s):
        '''Sort order: All rendered pages followed
        by their debug page, if any, followed by Postscript stub.
        Ghostscript documentation has the Postscript stub at the
        beginning, but it works at the end and also gets document info
        right that way.'''
        if s.endswith('.ps'):
            return 99999999
        key = int(os.path.basename(s)[0:6]) * 10
        if 'debug' in os.path.basename(s):
            key += 1
        return key

    pdf_pages = sorted(input_files, key=input_file_order)
    log.debug("Final pages: " + "\n".join(pdf_pages))
    ghostscript.generate_pdfa(pdf_pages, output_file, log, options.jobs or 1)


def merge_pages_qpdf(
        input_files,
        output_file,
        log,
        context):
    options = context.get_options()
    metadata_file = next(
        (ii for ii in input_files if ii.endswith('.repaired.pdf')))
    input_files.remove(metadata_file)

    def input_file_order(s):
        '''Sort order: All rendered pages followed
        by their debug page.'''
        key = int(os.path.basename(s)[0:6]) * 10
        if 'debug' in os.path.basename(s):
            key += 1
        return key

    pdf_pages = sorted(input_files, key=input_file_order)
    log.debug("Final pages: " + "\n".join(pdf_pages))

    reader_metadata = pypdf.PdfFileReader(metadata_file)
    pdfmark = get_pdfmark(reader_metadata, options)
    pdfmark['/Producer'] = 'qpdf ' + qpdf.version()

    first_page = pypdf.PdfFileReader(pdf_pages[0])

    writer = pypdf.PdfFileWriter()
    writer.appendPagesFromReader(first_page)
    writer.addMetadata(pdfmark)
    writer_file = pdf_pages[0].replace('.pdf', '.metadata.pdf')
    with open(writer_file, 'wb') as f:
        writer.write(f)

    pdf_pages[0] = writer_file

    qpdf.merge(pdf_pages, output_file)


def copy_final(
        input_files,
        output_file,
        log,
        context):
    input_file = next((ii for ii in input_files if ii.endswith('.pdf')))

    if output_file == '-':
        from shutil import copyfileobj
        with open(input_file, 'rb') as input_stream:
            copyfileobj(input_stream, sys.stdout.buffer)
    else:
        shutil.copy(input_file, output_file)


def build_pipeline(options, work_folder, log, context):
    main_pipeline = Pipeline.pipelines['main']

    # Triage
    task_triage = main_pipeline.transform(
        task_func=triage,
        input=os.path.join(work_folder, 'origin'),
        filter=formatter('(?i)'),
        output=os.path.join(work_folder, 'origin.pdf'),
        extras=[log, context])

    task_repair_pdf = main_pipeline.transform(
        task_func=repair_pdf,
        input=task_triage,
        filter=suffix('.pdf'),
        output='.repaired.pdf',
        output_dir=work_folder,
        extras=[log, context])

    # Split
    task_split_pages = main_pipeline.split(
        split_pages,
        task_repair_pdf,
        os.path.join(work_folder, '*.page.pdf'),
        extras=[log, context])

    # Rasterize preview
    task_rasterize_preview = main_pipeline.transform(
        task_func=rasterize_preview,
        input=task_split_pages,
        filter=suffix('.page.pdf'),
        output='.preview.jpg',
        output_dir=work_folder,
        extras=[log, context])
    task_rasterize_preview.active_if(options.rotate_pages)

    # Orient
    task_orient_page = main_pipeline.collate(
        task_func=orient_page,
        input=[task_split_pages, task_rasterize_preview],
        filter=regex(r".*/(\d{6})(\.ocr|\.skip)(?:\.page\.pdf|\.preview\.jpg)"),
        output=os.path.join(work_folder, r'\1\2.oriented.pdf'),
        extras=[log, context])

    # Rasterize actual
    task_rasterize_with_ghostscript = main_pipeline.transform(
        task_func=rasterize_with_ghostscript,
        input=task_orient_page,
        filter=suffix('.ocr.oriented.pdf'),
        output='.page.png',
        output_dir=work_folder,
        extras=[log, context])

    # Preprocessing subpipeline
    task_preprocess_remove_background = main_pipeline.transform(
        task_func=preprocess_remove_background,
        input=task_rasterize_with_ghostscript,
        filter=suffix(".page.png"),
        output=".pp-background.png",
        extras=[log, context])

    task_preprocess_deskew = main_pipeline.transform(
        task_func=preprocess_deskew,
        input=task_preprocess_remove_background,
        filter=suffix(".pp-background.png"),
        output=".pp-deskew.png",
        extras=[log, context])

    task_preprocess_clean = main_pipeline.transform(
        task_func=preprocess_clean,
        input=task_preprocess_deskew,
        filter=suffix(".pp-deskew.png"),
        output=".pp-clean.png",
        extras=[log, context])

    # HOCR OCR
    task_ocr_tesseract_hocr = main_pipeline.transform(
        task_func=ocr_tesseract_hocr,
        input=task_preprocess_clean,
        filter=suffix(".pp-clean.png"),
        output=".hocr",
        extras=[log, context])
    task_ocr_tesseract_hocr.graphviz(fillcolor='"#00cc66"')
    task_ocr_tesseract_hocr.active_if(options.pdf_renderer == 'hocr')

    task_select_image_for_pdf = main_pipeline.collate(
        task_func=select_image_for_pdf,
        input=[task_rasterize_with_ghostscript,
               task_preprocess_remove_background,
               task_preprocess_deskew,
               task_preprocess_clean],
        filter=regex(r".*/(\d{6})(?:\.page|\.pp-.*)\.png"),
        output=os.path.join(work_folder, r'\1.image'),
        extras=[log, context])
    task_select_image_for_pdf.graphviz(shape='diamond')

    task_select_image_layer = main_pipeline.collate(
        task_func=select_image_layer,
        input=[task_select_image_for_pdf, task_orient_page],
        filter=regex(r".*/(\d{6})(?:\.image|\.ocr\.oriented\.pdf)"),
        output=os.path.join(work_folder, r'\1.image-layer.pdf'),
        extras=[log, context])
    task_select_image_layer.graphviz(
        fillcolor='"#00cc66"', shape='diamond')
    task_select_image_layer.active_if(options.pdf_renderer == 'hocr')

    task_render_hocr_page = main_pipeline.transform(
        task_func=render_hocr_page,
        input=task_ocr_tesseract_hocr,
        filter=suffix('.hocr'),
        output='.hocr.pdf',
        extras=[log, context])
    task_render_hocr_page.graphviz(fillcolor='"#00cc66"')
    task_render_hocr_page.active_if(options.pdf_renderer == 'hocr')

    task_render_hocr_debug_page = main_pipeline.collate(
        task_func=render_hocr_debug_page,
        input=[task_select_image_for_pdf, task_ocr_tesseract_hocr],
        filter=regex(r".*/(\d{6})(?:\.image|\.hocr)"),
        output=os.path.join(work_folder, r'\1.debug.pdf'),
        extras=[log, context])
    task_render_hocr_debug_page.graphviz(fillcolor='"#00cc66"')
    task_render_hocr_debug_page.active_if(options.pdf_renderer == 'hocr')
    task_render_hocr_debug_page.active_if(options.debug_rendering)

    task_add_text_layer = main_pipeline.collate(
        task_func=add_text_layer,
        input=[task_render_hocr_page, task_select_image_layer],
        filter=regex(r".*/(\d{6})(?:\.hocr\.pdf|\.image-layer\.pdf)"),
        output=os.path.join(work_folder, r'\1.rendered.pdf'),
        extras=[log, context])
    task_add_text_layer.graphviz(fillcolor='"#00cc66"')
    task_add_text_layer.active_if(options.pdf_renderer == 'hocr')

    # Tesseract OCR
    task_tesseract_ocr_and_render_pdf = main_pipeline.collate(
        task_func=tesseract_ocr_and_render_pdf,
        input=[task_select_image_for_pdf, task_orient_page],
        filter=regex(r".*/(\d{6})(?:\.image|\.ocr\.oriented\.pdf)"),
        output=os.path.join(work_folder, r'\1.rendered.pdf'),
        extras=[log, context])
    task_tesseract_ocr_and_render_pdf.graphviz(fillcolor='"#66ccff"')
    task_tesseract_ocr_and_render_pdf.active_if(options.pdf_renderer == 'tesseract')

    # PDF/A
    task_generate_postscript_stub = main_pipeline.transform(
        task_func=generate_postscript_stub,
        input=task_repair_pdf,
        filter=formatter(r'\.repaired\.pdf'),
        output=os.path.join(work_folder, 'pdfa_def.ps'),
        extras=[log, context])
    task_generate_postscript_stub.active_if(options.output_type == 'pdfa')


    # Bypass valve
    task_skip_page = main_pipeline.transform(
        task_func=skip_page,
        input=task_orient_page,
        filter=suffix('.skip.oriented.pdf'),
        output='.done.pdf',
        output_dir=work_folder,
        extras=[log])

    # Merge pages
    task_merge_pages_ghostscript = main_pipeline.merge(
        task_func=merge_pages_ghostscript,
        input=[task_add_text_layer,
               task_render_hocr_debug_page,
               task_skip_page,
               task_tesseract_ocr_and_render_pdf,
               task_generate_postscript_stub],
        output=os.path.join(work_folder, 'merged.pdf'),
        extras=[log, context])
    task_merge_pages_ghostscript.active_if(options.output_type == 'pdfa')

    task_merge_pages_qpdf = main_pipeline.merge(
        task_func=merge_pages_qpdf,
        input=[task_add_text_layer,
               task_render_hocr_debug_page,
               task_skip_page,
               task_tesseract_ocr_and_render_pdf,
               task_repair_pdf],
        output=os.path.join(work_folder, 'merged.pdf'),
        extras=[log, context])
    task_merge_pages_qpdf.active_if(options.output_type == 'pdf')

    # Finalize
    task_copy_final = main_pipeline.merge(
        task_func=copy_final,
        input=[task_merge_pages_ghostscript, task_merge_pages_qpdf],
        output=options.output_file,
        extras=[log, context])