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132 lines
4.4 KiB
Python
132 lines
4.4 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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#
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# © 2015: jbarlow83 (https://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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from subprocess import Popen, PIPE
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import os
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import codecs
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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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/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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presentation is possible but this is preferable since it allows the output
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Postscript file to be completely ASCII.
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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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keywords=pdfmark_utf16.get('keywords', ''))
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return result
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def _get_postscript_icc_path():
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"Parse Ghostscript's help message to find where iccprofiles are stored"
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p_gs = Popen(['gs', '--help'], close_fds=True, universal_newlines=True,
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stdout=PIPE, stderr=PIPE)
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out, _ = p_gs.communicate()
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lines = out.splitlines()
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def search_paths(lines):
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seeking = True
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for line in lines:
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if seeking:
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if line.startswith('Search path'):
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seeking = False
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continue
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else:
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if line.strip().startswith('/'):
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yield from (
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path.strip() for path in line.split(':')
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if path.strip() != '')
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for root in search_paths(lines):
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path = os.path.realpath(os.path.join(root, '../iccprofiles'))
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if os.path.exists(path):
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return path
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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 = os.path.join(_get_postscript_icc_path(), 'srgb.icc')
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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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