James R. Barlow
83f9dfbac4
Someone reported a bug where the .png input to unpaper ended up being type 'P' (palette) for some reason, which was not supported in unpaper. Not sure how it happened, but seemed easier to fix by explicitly supporting. Here we use png256 if it would capture all colors in the input file. It's up to tesseract/reportlab to make use of the palette PNG when rendering.
146 lines
4.4 KiB
Python
146 lines
4.4 KiB
Python
#!/usr/bin/env python3
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# © 2015 James R. Barlow: github.com/jbarlow83
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from subprocess import Popen, PIPE
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from decimal import Decimal, getcontext
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import re
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import sys
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import PyPDF2 as pypdf
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FRIENDLY_COLORSPACE = {
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'/DeviceGray': 'gray',
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'/CalGray': 'gray',
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'/DeviceRGB': 'rgb',
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'/CalRGB': 'rgb',
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'/DeviceCMYK': 'cmyk',
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'/Lab': 'lab',
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'/ICCBased': 'icc',
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'/Indexed': 'index',
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'/Separation': 'sep',
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'/DeviceN': 'devn',
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'/Pattern': '-'
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}
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FRIENDLY_ENCODING = {
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'/CCITTFaxDecode': 'ccitt',
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'/DCTDecode': 'jpeg',
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'/JPXDecode': 'jpx',
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'/JBIG2Decode': 'jbig2',
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}
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FRIENDLY_COMP = {
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'gray': 1,
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'rgb': 3,
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'cmyk': 4,
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'lab': 3,
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'index': 1
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}
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def _page_has_inline_images(page):
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# PDF always uses \r\n for separator regardless of platform
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# Really basic heuristic that might trigger the odd false positive
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# This is only finds the first image and is not quite spec compliant
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try:
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contents = page.getContents()
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data = contents.getData()
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except AttributeError:
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# If we can't access the contents or data (empty page?) then there
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# are no inline images
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return False
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begin_image, image_data, end_image = False, False, False
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for data in re.split(b'\s+', data):
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if data == b'BI':
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begin_image = True
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elif data == b'ID':
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image_data = True
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elif data == b'EI':
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end_image = True
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if all((begin_image, image_data, end_image)):
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return True
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return False
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def _find_page_images(page, pageinfo):
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try:
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page['/Resources']['/XObject']
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except KeyError:
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return
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# Look for XObject (out of line images)
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for xobj in page['/Resources']['/XObject']:
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# PyPDF2 returns the keys as an iterator
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pdfimage = page['/Resources']['/XObject'][xobj]
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if pdfimage['/Subtype'] != '/Image':
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continue
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if '/ImageMask' in pdfimage:
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if pdfimage['/ImageMask']:
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continue
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image = {}
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image['width'] = pdfimage['/Width']
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image['height'] = pdfimage['/Height']
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image['bpc'] = pdfimage['/BitsPerComponent']
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if '/Filter' in pdfimage:
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filter_ = pdfimage['/Filter']
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if isinstance(filter_, pypdf.generic.ArrayObject):
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filter_ = filter_[0]
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image['enc'] = FRIENDLY_ENCODING.get(filter_, 'image')
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else:
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image['enc'] = 'image'
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if '/ColorSpace' in pdfimage:
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cs = pdfimage['/ColorSpace']
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if isinstance(cs, pypdf.generic.ArrayObject):
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cs = cs[0]
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image['color'] = FRIENDLY_COLORSPACE.get(cs, '-')
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else:
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image['color'] = 'jpx' if image['enc'] == 'jpx' else '?'
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image['comp'] = FRIENDLY_COMP.get(image['color'], '?')
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image['dpi_w'] = image['width'] / pageinfo['width_inches']
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image['dpi_h'] = image['height'] / pageinfo['height_inches']
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image['dpi'] = (image['dpi_w'] * image['dpi_h']) ** Decimal(0.5)
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yield image
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def _pdf_get_pageinfo(infile, page: int):
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pageinfo = {}
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pageinfo['pageno'] = page
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pageinfo['images'] = []
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pdf = pypdf.PdfFileReader(infile)
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page = pdf.pages[page - 1]
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text = page.extractText()
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pageinfo['has_text'] = (text.strip() != '')
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width_pt = page['/MediaBox'][2] - page['/MediaBox'][0]
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height_pt = page['/MediaBox'][3] - page['/MediaBox'][1]
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pageinfo['width_inches'] = width_pt / Decimal(72.0)
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pageinfo['height_inches'] = height_pt / Decimal(72.0)
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pageinfo['images'] = [im for im in _find_page_images(page, pageinfo)]
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# Look for inline images
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if _page_has_inline_images(page):
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raise NotImplementedError(
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"Warning: input PDF contains inline images - not supported")
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if pageinfo['images']:
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xres = max(image['dpi_w'] for image in pageinfo['images'])
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yres = max(image['dpi_h'] for image in pageinfo['images'])
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pageinfo['xres'], pageinfo['yres'] = xres, yres
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pageinfo['width_pixels'] = \
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int(round(xres * pageinfo['width_inches']))
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pageinfo['height_pixels'] = \
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int(round(yres * pageinfo['height_inches']))
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return pageinfo
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def pdf_get_all_pageinfo(infile):
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pdf = pypdf.PdfFileReader(infile)
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getcontext().prec = 6
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return [_pdf_get_pageinfo(infile, n) for n in range(pdf.numPages)]
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