James R. Barlow
c1e18bb825
Soft masks are only allowed to be of colorspace DeviceGray so we shouldn't use pngquant on them. For now, avoid this exceptional case by excluded soft masks from optimization.
486 lines
16 KiB
Python
486 lines
16 KiB
Python
# © 2018 James R. Barlow: github.com/jbarlow83
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#
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# This file is part of OCRmyPDF.
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#
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# OCRmyPDF is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# OCRmyPDF is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with OCRmyPDF. If not, see <http://www.gnu.org/licenses/>.
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from pathlib import Path
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import concurrent.futures
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from collections import defaultdict, namedtuple
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import logging
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import sys
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from PIL import Image
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import pikepdf
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from ._jobcontext import JobContext
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from . import leptonica
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from .helpers import re_symlink, fspath
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from .exec import pngquant, jbig2enc
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DEFAULT_JPEG_QUALITY = 75
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DEFAULT_PNG_QUALITY = 70
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def img_name(root, xref, ext):
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return fspath(root / '{:08d}{}'.format(xref, ext))
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def png_name(root, xref):
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return img_name(root, xref, '.png')
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def jpg_name(root, xref):
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return img_name(root, xref, '.jpg')
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def tif_name(root, xref):
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return img_name(root, xref, '.tif')
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def extract_image_filter(pike, root, log, image, xref):
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if image.Subtype != '/Image':
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return None
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if image.Length < 100:
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log.debug("Skipping small image, xref %s", xref)
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return None
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pim = pikepdf.PdfImage(image)
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if len(pim.filter_decodeparms) > 1:
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log.debug("Skipping multiply filtered, xref %s", xref)
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return None
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filtdp = pim.filter_decodeparms[0]
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if pim.bits_per_component > 8:
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return None # Don't mess with wide gamut images
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if filtdp[0] == '/JPXDecode':
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return None # Don't do JPEG2000
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return pim, filtdp
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def extract_image_jbig2(*, pike, root, log, image, xref, options):
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result = extract_image_filter(pike, root, log, image, xref)
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if result is None:
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return None
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pim, filtdp = result
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if pim.bits_per_component == 1 \
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and filtdp != '/JBIG2Decode' \
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and jbig2enc.available():
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try:
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imgname = Path(root / '{:08d}'.format(xref))
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with imgname.open('wb') as f:
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ext = pim.extract_to(stream=f)
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imgname.rename(imgname.with_suffix(ext))
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except pikepdf.UnsupportedImageTypeError:
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return None
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return xref, ext
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return None
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def extract_image_generic(*, pike, root, log, image, xref, options):
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result = extract_image_filter(pike, root, log, image, xref)
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if result is None:
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return None
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pim, filtdp = result
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if filtdp[0] == '/DCTDecode' \
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and options.optimize >= 2:
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# This is a simple heuristic derived from some training data, that has
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# about a 70% chance of guessing whether the JPEG is high quality,
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# and possibly recompressible, or not. The number itself doesn't mean
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# anything.
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# bytes_per_pixel = int(raw_jpeg.Length) / (w * h)
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# jpeg_quality_estimate = 117.0 * (bytes_per_pixel ** 0.213)
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# if jpeg_quality_estimate < 65:
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# return None
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# We could get the ICC profile here, but there's no need to look at it
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# for quality transcoding
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# if icc:
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# stream = BytesIO(raw_jpeg.read_raw_bytes())
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# iccbytes = icc.read_bytes()
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# with Image.open(stream) as im:
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# im.save(jpg_name(root, xref), icc_profile=iccbytes)
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try:
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imgname = Path(root / '{:08d}'.format(xref))
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with imgname.open('wb') as f:
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ext = pim.extract_to(stream=f)
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imgname.rename(imgname.with_suffix(ext))
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except pikepdf.UnsupportedImageTypeError:
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return None
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return xref, ext
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elif pim.indexed \
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and pim.colorspace in pim.SIMPLE_COLORSPACES \
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and options.optimize >= 3:
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# Try to improve on indexed images - these are far from low hanging
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# fruit in most cases
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pim.as_pil_image().save(png_name(root, xref))
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return xref, '.png'
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elif not pim.indexed and pim.colorspace in pim.SIMPLE_COLORSPACES:
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# An optimization opportunity here, not currently taken, is directly
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# generating a PNG from compressed data
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pim.as_pil_image().save(png_name(root, xref))
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return xref, '.png'
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else:
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return None
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return True
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def extract_images(pike, root, log, options, extract_fn):
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"""Extract image using extract_fn
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extract_fn decides where the image is interesting in this case
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"""
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include_xrefs = set()
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exclude_xrefs = set()
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errors = 0
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for pageno, page in enumerate(pike.pages):
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try:
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xobjs = page.Resources.XObject
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except AttributeError:
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continue
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for _imname, image in dict(xobjs).items():
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if image.objgen[1] != 0:
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continue # Ignore images in an incremental PDF
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xref = image.objgen[0]
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if hasattr(image, 'SMask'):
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# Ignore soft masks
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smask_xref = image.SMask.objgen[0]
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exclude_xrefs.add(smask_xref)
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include_xrefs.add(xref)
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working_xrefs = include_xrefs - exclude_xrefs
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for xref in working_xrefs:
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image = pike.get_object((xref, 0))
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try:
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result = extract_fn(
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pike=pike, root=root, log=log, image=image,
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xref=xref, options=options
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)
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except Exception as e:
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log.debug("Image xref %s", xref)
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log.debug(repr(e))
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errors += 1
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else:
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if result:
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_, ext = result
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yield pageno, xref, ext
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def extract_images_generic(pike, root, log, options):
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"""Extract any >=2bpp image we think we can improve"""
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jpegs = []
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pngs = []
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for _, xref, ext in extract_images(
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pike, root, log, options, extract_image_generic):
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log.debug('xref = %s ext = %s', xref, ext)
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if ext == '.png':
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pngs.append(xref)
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elif ext == '.jpg':
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jpegs.append(xref)
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log.debug(
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"Optimizable images: "
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"JPEGs: %s PNGs: %s", len(jpegs), len(pngs)
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)
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return jpegs, pngs
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def extract_images_jbig2(pike, root, log, options):
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"""Extract any bitonal image that we think we can improve as JBIG2"""
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jbig2_groups = defaultdict(list)
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for pageno, xref, ext in extract_images(
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pike, root, log, options, extract_image_jbig2):
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group = pageno // options.jbig2_page_group_size
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jbig2_groups[group].append((xref, ext))
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# Elide empty groups
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jbig2_groups = {group: xrefs for group, xrefs in jbig2_groups.items()
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if len(xrefs) > 0}
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log.debug(
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"Optimizable images: "
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"JBIG2 groups: %s", (len(jbig2_groups),)
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)
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return jbig2_groups
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def _produce_jbig2_images(jbig2_groups, root, log, options):
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"""Produce JBIG2 images from their groups"""
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def jbig2_group_futures(executor, root, groups):
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for group, xref_exts in groups.items():
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prefix = 'group{:08d}'.format(group)
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future = executor.submit(
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jbig2enc.convert_group,
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cwd=fspath(root),
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infiles=(img_name(root, xref, ext) for xref, ext in xref_exts),
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out_prefix=prefix
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)
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yield future
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def jbig2_single_futures(executor, root, groups):
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for group, xref_exts in groups.items():
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prefix = 'group{:08d}'.format(group)
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# Second loop is to ensure multiple images per page are unpacked
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for n, xref_ext in enumerate(xref_exts):
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xref, ext = xref_ext
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future = executor.submit(
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jbig2enc.convert_single,
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cwd=fspath(root),
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infile=img_name(root, xref, ext),
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outfile=root / ('{}.{:04d}'.format(prefix, n))
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)
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yield future
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if options.jbig2_page_group_size > 1:
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jbig2_futures = jbig2_group_futures
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else:
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jbig2_futures = jbig2_single_futures
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with concurrent.futures.ThreadPoolExecutor(
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max_workers=options.jobs) as executor:
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futures = jbig2_futures(executor, root, jbig2_groups)
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for future in concurrent.futures.as_completed(futures):
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proc = future.result()
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log.debug(proc.stderr.decode())
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def convert_to_jbig2(pike, jbig2_groups, root, log, options):
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"""Convert images to JBIG2 and insert into PDF.
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When the JBIG2 page group size is > 1 we do several JBIG2 images at once
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and build a symbol dictionary that will span several pages. Each JBIG2
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image must reference to its symbol dictionary. If too many pages shared the
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same dictionary JBIG2 encoding becomes more expensive and less efficient.
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The default value of 10 was determined through testing. Currently this
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must be lossy encoding since jbig2enc does not support refinement coding.
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When the JBIG2 symbolic coder is not used, each JBIG2 stands on its own
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and needs no dictionary. Currently this is must be lossless JBIG2.
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"""
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_produce_jbig2_images(jbig2_groups, root, log, options)
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for group, xref_exts in jbig2_groups.items():
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prefix = 'group{:08d}'.format(group)
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jbig2_symfile = root / (prefix + '.sym')
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if jbig2_symfile.exists():
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jbig2_globals_data = jbig2_symfile.read_bytes()
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jbig2_globals = pikepdf.Stream(pike, jbig2_globals_data)
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jbig2_globals_dict = pikepdf.Dictionary({
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'/JBIG2Globals': jbig2_globals
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})
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elif options.jbig2_page_group_size == 1:
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jbig2_globals_dict = None
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else:
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raise FileNotFoundError(jbig2_symfile)
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for n, xref_ext in enumerate(xref_exts):
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xref, _ = xref_ext
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jbig2_im_file = root / (prefix + '.{:04d}'.format(n))
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jbig2_im_data = jbig2_im_file.read_bytes()
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im_obj = pike.get_object(xref, 0)
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im_obj.write(
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jbig2_im_data, pikepdf.Name('/JBIG2Decode'),
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jbig2_globals_dict
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)
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def transcode_jpegs(pike, jpegs, root, log, options):
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for xref in jpegs:
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in_jpg = Path(jpg_name(root, xref))
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opt_jpg = in_jpg.with_suffix('.opt.jpg')
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# This produces a debug warning from PIL
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# DEBUG:PIL.Image:Error closing: 'NoneType' object has no attribute
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# 'close'. Seems to be mostly harmless
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# https://github.com/python-pillow/Pillow/issues/1144
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with Image.open(fspath(in_jpg)) as im:
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im.save(fspath(opt_jpg),
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optimize=True,
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quality=options.jpeg_quality)
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# pylint: disable=no-member
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if opt_jpg.stat().st_size > in_jpg.stat().st_size:
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log.debug("xref %s, jpeg, made larger - skip", xref)
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continue
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compdata = leptonica.CompressedData.open(opt_jpg)
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im_obj = pike.get_object(xref, 0)
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im_obj.write(
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compdata.read(), filter=pikepdf.Name('/DCTDecode')
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)
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def transcode_pngs(pike, pngs, root, log, options):
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if options.optimize >= 2:
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png_quality = (
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max(10, options.png_quality - 10),
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min(100, options.png_quality + 10)
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)
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with concurrent.futures.ThreadPoolExecutor(
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max_workers=options.jobs) as executor:
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for xref in pngs:
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executor.submit(
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pngquant.quantize,
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png_name(root, xref), png_name(root, xref),
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png_quality[0], png_quality[1])
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for xref in pngs:
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im_obj = pike.get_object(xref, 0)
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# Open, transcode (!), package for PDF
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try:
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pix = leptonica.Pix.open(png_name(root, xref))
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if pix.depth == 1:
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pix = pix.invert() # PDF assumes 1 is black for monochrome
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compdata = pix.generate_pdf_ci_data(
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leptonica.lept.L_FLATE_ENCODE, 0
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)
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except leptonica.LeptonicaError as e:
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log.error(e)
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continue
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# This is what we should be doing: open the compressed data without
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# transcoding. However this shifts each pixel row by one for some
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# reason.
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#compdata = leptonica.CompressedData.open(png_name(root, xref))
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if len(compdata) > int(im_obj.stream_dict.Length):
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continue # If we produced a larger image, don't use
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predictor = None
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if compdata.predictor > 0:
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predictor = pikepdf.Dictionary({'/Predictor': compdata.predictor})
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im_obj.BitsPerComponent = compdata.bps
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im_obj.Width = compdata.w
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im_obj.Height = compdata.h
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if compdata.ncolors > 0:
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palette_pdf_string = compdata.get_palette_pdf_string()
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palette_data = pikepdf.Object.parse(palette_pdf_string)
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palette_stream = pikepdf.Stream(pike, bytes(palette_data))
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palette = [pikepdf.Name('/Indexed'), pikepdf.Name('/DeviceRGB'),
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compdata.ncolors - 1, palette_stream]
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cs = palette
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else:
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if compdata.spp == 1:
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cs = pikepdf.Name('/DeviceGray')
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elif compdata.spp == 3:
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cs = pikepdf.Name('/DeviceRGB')
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elif compdata.spp == 4:
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cs = pikepdf.Name('/DeviceCMYK')
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im_obj.ColorSpace = cs
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im_obj.write(
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compdata.read(),
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filter=pikepdf.Name('/FlateDecode'), decode_parms=predictor
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)
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def optimize(
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input_file,
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output_file,
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log,
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context):
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options = context.get_options()
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if options.optimize == 0:
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re_symlink(input_file, output_file, log)
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return
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if options.jpeg_quality == 0:
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options.jpeg_quality = \
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DEFAULT_JPEG_QUALITY if options.optimize < 3 else 40
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if options.png_quality == 0:
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options.png_quality = \
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DEFAULT_PNG_QUALITY if options.optimize < 3 else 30
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if options.jbig2_page_group_size == 0:
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options.jbig2_page_group_size = \
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10 if options.jbig2_lossy else 1
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pike = pikepdf.Pdf.open(input_file)
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root = Path(output_file).parent / 'images'
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root.mkdir(exist_ok=True) # pylint: disable=no-member
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jpegs, pngs = extract_images_generic(pike, root, log, options)
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transcode_jpegs(pike, jpegs, root, log, options)
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transcode_pngs(pike, pngs, root, log, options)
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jbig2_groups = extract_images_jbig2(pike, root, log, options)
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convert_to_jbig2(pike, jbig2_groups, root, log, options)
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target_file = Path(output_file).with_suffix('.opt.pdf')
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pike.save(target_file, preserve_pdfa=True,
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object_stream_mode=pikepdf.ObjectStreamMode.generate)
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input_size = Path(input_file).stat().st_size
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output_size = Path(target_file).stat().st_size
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ratio = input_size / output_size
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savings = 1 - output_size / input_size
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log.info("Optimize ratio: {:.2f} savings: {:.1f}%".format(
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ratio, 100 * savings))
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if savings < 0:
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log.info("Optimize did not improve the file - discarded")
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re_symlink(input_file, output_file, log)
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else:
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re_symlink(target_file, output_file, log)
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def main(infile, outfile, level, jobs=1):
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from tempfile import TemporaryDirectory
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from shutil import copy
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class OptimizeOptions:
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"""Emulate ocrmypdf's options"""
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def __init__(
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self, jobs, optimize, jpeg_quality, png_quality, jb2lossy):
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self.jobs = jobs
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self.optimize = optimize
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self.jpeg_quality = jpeg_quality
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self.png_quality = png_quality
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self.jbig2_page_group_size = 0
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self.jbig2_lossy = jb2lossy
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logging.basicConfig(level=logging.DEBUG)
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log = logging.getLogger()
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ctx = JobContext()
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options = OptimizeOptions(
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jobs=jobs,
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optimize=int(level),
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jpeg_quality=0, # Use default
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png_quality=0,
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jb2lossy=False
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)
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ctx.set_options(options)
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with TemporaryDirectory() as td:
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tmpout = Path(td) / 'out.pdf'
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optimize(infile, tmpout, log, ctx)
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copy(fspath(tmpout), fspath(outfile))
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if __name__ == '__main__':
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main(sys.argv[1], sys.argv[2], sys.argv[3])
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