James R. Barlow
ebe68de4ff
Tests mostly passing. For the moment this is the new default. Although PyPDF2 produces a PDF-1.3 which will be wrong for some contents and possible should be repaired with qpdf. Again. Looks like it could work better to merge PyPDF2 and fix everything with qpdf.
111 lines
3.7 KiB
Python
111 lines
3.7 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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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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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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# Since PostScript might not handle UTF-8 (it's hard to get a clear
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# answer), insist on ascii
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with open(target_filename, 'w', encoding='ascii') as f:
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f.write(ps)
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