159 lines
5.2 KiB
Python
159 lines
5.2 KiB
Python
#!/usr/bin/env python3
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# © 2015 James R. Barlow: github.com/jbarlow83
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#
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# Generate a PDFA_def.ps file for Ghostscript >= 9.14
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from __future__ import print_function, absolute_import, division
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from string import Template
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import codecs
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import pkg_resources
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import PyPDF2 as pypdf
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ICC_PROFILE_RELPATH = 'data/sRGB.icc'
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SRGB_ICC_PROFILE = pkg_resources.resource_filename(
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'ocrmypdf', ICC_PROFILE_RELPATH)
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# This is a template written in PostScript which is needed to create PDF/A
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# files, from the Ghostscript documentation. Lines beginning with % are
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# comments. Python substitution variables have a '$' prefix.
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pdfa_def_template = u"""%!
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% This is a sample prefix file for creating a PDF/A document.
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% Feel free to modify entries marked with "Customize".
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% This assumes an ICC profile to reside in the file (ISO Coated sb.icc),
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% unless the user modifies the corresponding line below.
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% Define entries in the document Info dictionary :
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/ICCProfile ($icc_profile)
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def
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[ /Title <$title>
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/Author <$author>
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/Subject <$subject>
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/Keywords <$keywords>
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/Creator <$creator>
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/DOCINFO pdfmark
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% Define an ICC profile :
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[/_objdef {icc_PDFA} /type /stream /OBJ pdfmark
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[{icc_PDFA}
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<<
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/N currentpagedevice /ProcessColorModel known {
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currentpagedevice /ProcessColorModel get dup /DeviceGray eq
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{pop 1} {
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/DeviceRGB eq
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{3}{4} ifelse
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} ifelse
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} {
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(ERROR, unable to determine ProcessColorModel) == flush
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} ifelse
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>> /PUT pdfmark
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[{icc_PDFA} ICCProfile (r) file /PUT pdfmark
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% Define the output intent dictionary :
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[/_objdef {OutputIntent_PDFA} /type /dict /OBJ pdfmark
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[{OutputIntent_PDFA} <<
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/Type /OutputIntent % Must be so (the standard requires).
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/S /GTS_PDFA1 % Must be so (the standard requires).
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/DestOutputProfile {icc_PDFA} % Must be so (see above).
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/OutputConditionIdentifier ($icc_identifier)
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>> /PUT pdfmark
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[{Catalog} <</OutputIntents [ {OutputIntent_PDFA} ]>> /PUT pdfmark
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"""
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def encode_text_string(s: str) -> str:
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'''Encode text string to hex string for use in a PDF
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From PDF 32000-1:2008 a string object may be included in hexademical form
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if it is enclosed in angle brackets. For general Unicode the string should
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be UTF-16 (big endian) with byte order marks. A non-hexademical
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representation is doable but this is preferable since it allows the output
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Postscript file to be completely ASCII and no escaping of Postscript
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characters is necessary.
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'''
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# Sometimes lazy C programmer leave their NULs at the end of strings
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# tests/resources/aspect.pdf is one example (created by ImageMagick)
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s = s.replace('\x00', '')
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if s == '':
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return ''
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utf16_bytes = s.encode('utf-16be')
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ascii_hex_bytes = codecs.encode(b'\xfe\xff' + utf16_bytes, 'hex')
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ascii_hex_str = ascii_hex_bytes.decode('ascii').lower()
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return ascii_hex_str
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def _get_pdfa_def(icc_profile, icc_identifier, pdfmark):
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pdfmark_utf16 = {k: encode_text_string(v) for k, v in pdfmark.items()}
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t = Template(pdfa_def_template)
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result = t.substitute(icc_profile=icc_profile,
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icc_identifier=icc_identifier,
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title=pdfmark_utf16.get('/Title', ''),
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author=pdfmark_utf16.get('/Author', ''),
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subject=pdfmark_utf16.get('/Subject', ''),
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creator=pdfmark_utf16.get('/Creator', ''),
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keywords=pdfmark_utf16.get('/Keywords', ''))
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return result
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def generate_pdfa_def(target_filename, pdfmark, icc='sRGB'):
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if icc == 'sRGB':
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icc_profile = SRGB_ICC_PROFILE
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else:
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raise NotImplementedError("Only supporting sRGB")
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ps = _get_pdfa_def(icc_profile, icc, pdfmark)
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# We should have encoded everything to pure ASCII by this point, and
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# to be safe, only allow ASCII in PostScript
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with open(target_filename, 'w', encoding='ascii') as f:
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f.write(ps)
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def file_claims_pdfa(filename):
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"""Determines if the file claims to be PDF/A compliant
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Checking if a file is a truly compliant PDF/A is a massive undertaking
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that no open source tool does properly. Some commercial tools are
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generally reliable (Acrobat).
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This checks if the XMP metadata contains a PDF/A marker.
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"""
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pdf = pypdf.PdfFileReader(filename)
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xmp = pdf.getXmpMetadata()
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try:
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pdfa_nodes = xmp.getNodesInNamespace(
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aboutUri='',
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namespace='http://www.aiim.org/pdfa/ns/id/')
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except AttributeError:
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return {'pass': False, 'output': 'pdf', 'message': 'No XMP metadata'}
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pdfa_dict = {attr.localName: attr.value for attr in pdfa_nodes}
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pdfa_dict['pass'] = False
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pdfa_dict['output'] = 'pdf'
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if pdfa_dict:
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part_conformance = pdfa_dict['part'] + pdfa_dict['conformance']
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valid_part_conforms = {'1A', '1B', '2A', '2B', '2U', '3A', '3B', '3U'}
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message = 'File claims to be PDF/A-{}'.format(
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part_conformance)
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if part_conformance in valid_part_conforms:
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pdfa_dict['pass'] = True
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pdfa_dict['output'] = 'pdfa'
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pdfa_dict['message'] = message
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else:
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pdfa_dict['message'] = 'File is a regular PDF'
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return pdfa_dict
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