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Most image viewers can't display JBIG2 files. All PDF viewers can display JBIG2 files. This is useful for checking that PDF viewers render JBIG2 files the same way we do.
149 lines
3.6 KiB
Python
Executable File
149 lines
3.6 KiB
Python
Executable File
#!/usr/bin/env python3
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"""
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Creates a PDF that embeds a jbig2 image. Useful for viewing .jbig2 files in
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PDF viewers, since all PDF viewers support .jbig2 but few image viewers do.
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Usage is a bit clunky (use Build/lagom/bin/file to get the dimensions):
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% Meta/jbig2_to_pdf.py -o foo.pdf path/to/bitmap.jbig2 399 400
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% open foo.pdf
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"""
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import argparse
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import sys
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import textwrap
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def dedent(b):
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return textwrap.dedent(b.decode('latin1')).encode('latin1')
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def main():
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parser = argparse.ArgumentParser(
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epilog=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
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)
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parser.add_argument("image", help="Input image")
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parser.add_argument("width", type=int, help="image width")
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parser.add_argument("height", type=int, help="image height")
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parser.add_argument("-o", "--output", help="Path to output PDF")
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args = parser.parse_args()
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width, height = args.width, args.height
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with open(args.image, 'rb') as f:
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image_data = f.read()
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print(f'dims {width}x{height}')
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# strip jbig2 header
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image_data = image_data[8:]
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if image_data[0] & 1 == 0:
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print('random-access jbig2 does not work', file=sys.stderr)
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sys.exit(1)
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if image_data[0] & 2 == 0:
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image_data = image_data[4:]
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image_data = image_data[1:]
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start = dedent(b'''\
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%PDF-1.4
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%\265\266
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''')
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objs = [dedent(b'''\
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1 0 obj
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<<
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/Type /Catalog
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/Pages 2 0 R
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>>
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endobj
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'''),
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dedent(b'''\
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2 0 obj
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<<
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/Type /Pages
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/Kids [3 0 R]
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/Count 1
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>>
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endobj
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'''),
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dedent(b'''\
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3 0 obj
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<<
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/Type /Page
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/Parent 2 0 R
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/MediaBox [0 0 %d %d]
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/Contents 4 0 R
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/Resources <<
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/XObject <<
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/Im 5 0 R
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>>
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>>
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>>
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endobj
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''' % (width, height)),
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dedent(b'''\
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4 0 obj
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<</Length 25>>
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stream
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%d 0 0 %d 0 0 cm
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/Im Do
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endstream
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endobj
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''' % (width, height)),
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dedent(b'''\
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5 0 obj
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<<
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/Length %d
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/Type /XObject
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/Subtype /Image
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/Width %d
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/Height %d
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/ColorSpace /DeviceGray
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/Filter /JBIG2Decode
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/BitsPerComponent 1
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>>
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stream
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''' % (len(image_data), width, height)) +
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image_data +
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dedent(b'''
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endstream
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endobj
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'''),
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]
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with open(args.output, 'wb') as f:
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f.write(start)
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offsets = []
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for obj in objs:
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offsets.append(f.tell())
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f.write(obj)
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f.write(b'\n')
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xref_offset = f.tell()
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f.write(b'xref\n')
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f.write(b'0 %d\n' % (len(objs) + 1))
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f.write(b'0000000000 65536 f \n')
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for offset in offsets:
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f.write(b'%010d 00000 n \n' % offset)
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f.write(b'\n')
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f.write(dedent(b'''\
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trailer
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<<
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/Size %d
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/Root 1 0 R
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>>
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startxref
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%d
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%%%%EOF
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''' % (len(objs) + 1, xref_offset)))
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if __name__ == '__main__':
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main()
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