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