332 lines
11 KiB
Python
332 lines
11 KiB
Python
#!/usr/bin/env python3
|
|
# © 2015 James R. Barlow: github.com/jbarlow83
|
|
|
|
from subprocess import Popen, PIPE
|
|
from decimal import Decimal, getcontext
|
|
import re
|
|
import sys
|
|
import PyPDF2 as pypdf
|
|
from collections import namedtuple
|
|
|
|
matrix_mult = pypdf.pdf.utils.matrixMultiply
|
|
|
|
FRIENDLY_COLORSPACE = {
|
|
'/DeviceGray': 'gray',
|
|
'/CalGray': 'gray',
|
|
'/DeviceRGB': 'rgb',
|
|
'/CalRGB': 'rgb',
|
|
'/DeviceCMYK': 'cmyk',
|
|
'/Lab': 'lab',
|
|
'/ICCBased': 'icc',
|
|
'/Indexed': 'index',
|
|
'/Separation': 'sep',
|
|
'/DeviceN': 'devn',
|
|
'/Pattern': '-',
|
|
'/G': 'gray', # Abbreviations permitted in inline images
|
|
'/RGB': 'rgb',
|
|
'/CMYK': 'cmyk',
|
|
'/I': 'index',
|
|
}
|
|
|
|
FRIENDLY_ENCODING = {
|
|
'/CCITTFaxDecode': 'ccitt',
|
|
'/DCTDecode': 'jpeg',
|
|
'/JPXDecode': 'jpx',
|
|
'/JBIG2Decode': 'jbig2',
|
|
'/CCF': 'ccitt', # Abbreviations permitted in inline images
|
|
'/DCT': 'jpeg'
|
|
}
|
|
|
|
FRIENDLY_COMP = {
|
|
'gray': 1,
|
|
'rgb': 3,
|
|
'cmyk': 4,
|
|
'lab': 3,
|
|
'index': 1
|
|
}
|
|
|
|
|
|
def _matrix_from_shorthand(shorthand):
|
|
"""Convert from PDF matrix shorthand to full matrix
|
|
|
|
PDF 1.7 spec defines a shorthand for describing the entries of a matrix
|
|
since the last column is always (0, 0, 1).
|
|
"""
|
|
|
|
a, b, c, d, e, f = map(float, shorthand)
|
|
return ((a, b, 0),
|
|
(c, d, 0),
|
|
(e, f, 1))
|
|
|
|
|
|
def _shorthand_from_matrix(matrix):
|
|
"""Convert from transformation matrix to PDF shorthand."""
|
|
a, b = matrix[0][0], matrix[0][1]
|
|
c, d = matrix[1][0], matrix[1][1]
|
|
e, f = matrix[2][0], matrix[2][1]
|
|
return tuple(map(float, (a, b, c, d, e, f)))
|
|
|
|
|
|
def euclidean_distance(rowvec1, rowvec2):
|
|
return ((rowvec1[0] - rowvec2[0]) ** 2
|
|
+ (rowvec1[1] - rowvec2[1]) ** 2) ** 0.5
|
|
|
|
|
|
ContentsInfo = namedtuple('ContentsInfo',
|
|
['raster_settings', 'inline_images'])
|
|
|
|
def _interpret_contents(contentstream):
|
|
operations = contentstream.operations
|
|
stack = []
|
|
ctm = _matrix_from_shorthand((1, 0, 0, 1, 0, 0))
|
|
image_raster_settings = []
|
|
inline_images = []
|
|
|
|
print(operations)
|
|
for op in operations:
|
|
operands, command = op
|
|
if command == b'q':
|
|
stack.append(ctm)
|
|
elif command == b'Q':
|
|
ctm = stack.pop()
|
|
elif command == b'cm':
|
|
ctm = matrix_mult(
|
|
ctm, _matrix_from_shorthand(operands))
|
|
elif command == b'Do':
|
|
image_name = operands[0]
|
|
image_raster_settings.append(
|
|
(image_name, _shorthand_from_matrix(ctm)))
|
|
elif command == b'INLINE IMAGE':
|
|
settings = operands['settings']
|
|
inline_images.append(
|
|
(settings, _shorthand_from_matrix(ctm)))
|
|
|
|
return ContentsInfo(
|
|
raster_settings=image_raster_settings,
|
|
inline_images=inline_images)
|
|
|
|
|
|
def _get_dpi(ctm_shorthand, image_size):
|
|
"""Given the transformation matrix and image size, find the image DPI.
|
|
|
|
PDFs do not include image resolution information within image data.
|
|
Instead, the PDF page content stream describes the location where the
|
|
image will be rasterized, and the effective resolution is the ratio of the
|
|
pixel size to raster target size.
|
|
|
|
Normally a scanned PDF has the paper size set appropriately but this is
|
|
not guaranteed. The most common case is a cropped image will change the
|
|
page size (/CropBox) without altering the page content stream. That means
|
|
it is not sufficient to assume that the image fills the page, even though
|
|
that is the most common case.
|
|
|
|
This code solves the general case where the image may be scaled (always),
|
|
cropped, translated (often), and rotated in place (occasionally) to an
|
|
arbitrary angle (rare). It will work as long as the image is a
|
|
parallelogram from the perspective of a rectilinear coordinate system.
|
|
It does not work for arbitrarily quadrilaterals that might be produced
|
|
by shearing, but by that point DPI becomes a linear gradient rather than
|
|
constant over the image.
|
|
|
|
The transformation matrix describes the coordinate system at the time of
|
|
rendering. We transform the image corner locations into the coordinate
|
|
system and measure the width and height within the system, expressed in
|
|
PDF units. From there we can compare to the actual image dimensions.
|
|
|
|
pdfimages -list does calculate the DPI in some way that is not completely
|
|
naive, but it does not the DPI of rotated images right, so cannot be
|
|
used anymore to validate this. Photoshop works, or using Acrobat to
|
|
rotate the image back to normal.
|
|
|
|
It does not matter if the image is partially cropped, or even out of the
|
|
/MediaBox.
|
|
|
|
"""
|
|
matrix = _matrix_from_shorthand(ctm_shorthand)
|
|
|
|
# Corners of the image in untransformed unit space; last
|
|
# column is a dummy to assist matrix math
|
|
corners = [[0, 0, 1],
|
|
[1, 0, 1],
|
|
[0, 1, 1],
|
|
[1, 1, 1]]
|
|
|
|
# Rotate/translate/scale the corners into PDF coords (1/72")
|
|
# ordering of points may change, e.g. if rotation is 180 then
|
|
# the point (0, 0) may become the top right
|
|
# The row vectors can all be transformed together here by building
|
|
# a matrix of them
|
|
page_unit_corners = matrix_mult(corners, matrix)
|
|
|
|
# Calculate the width and height of the rotated image
|
|
# the transformation matrix so the corner that was originally
|
|
# (1, 1) can be ignored
|
|
image_drawn_width = euclidean_distance(
|
|
page_unit_corners[0], page_unit_corners[1])
|
|
image_drawn_height = euclidean_distance(
|
|
page_unit_corners[0], page_unit_corners[2])
|
|
|
|
# print((image_drawn_width, image_drawn_height))
|
|
|
|
# The scale of the image is pixels per PDF unit (1/72")
|
|
scale_w = image_size[0] / image_drawn_width
|
|
scale_h = image_size[1] / image_drawn_height
|
|
|
|
# DPI = scale * 72
|
|
dpi_w = scale_w * 72.0
|
|
dpi_h = scale_h * 72.0
|
|
|
|
return (dpi_w, dpi_h)
|
|
|
|
|
|
def _find_page_images(page, pageinfo, contentsinfo):
|
|
|
|
for n, im in enumerate(contentsinfo.inline_images):
|
|
print(n)
|
|
settings, shorthand = im
|
|
image = {}
|
|
image['name'] = str('inline-%02d' % n)
|
|
image['width'] = settings['/W']
|
|
image['height'] = settings['/H']
|
|
image['bpc'] = settings['/BPC']
|
|
image['color'] = FRIENDLY_COLORSPACE.get(settings['/CS'], '-')
|
|
image['comp'] = FRIENDLY_COMP.get(image['color'], '?')
|
|
|
|
dpi_w, dpi_h = _get_dpi(shorthand, (image['width'], image['height']))
|
|
image['dpi_w'], image['dpi_h'] = Decimal(dpi_w), Decimal(dpi_h)
|
|
yield image
|
|
|
|
# Look for XObject (out of line images)
|
|
try:
|
|
page['/Resources']['/XObject']
|
|
except KeyError:
|
|
return
|
|
for xobj in page['/Resources']['/XObject']:
|
|
# PyPDF2 returns the keys as an iterator
|
|
pdfimage = page['/Resources']['/XObject'][xobj]
|
|
if pdfimage['/Subtype'] != '/Image':
|
|
continue
|
|
if '/ImageMask' in pdfimage:
|
|
if pdfimage['/ImageMask']:
|
|
continue
|
|
image = {}
|
|
image['name'] = str(xobj)
|
|
image['width'] = pdfimage['/Width']
|
|
image['height'] = pdfimage['/Height']
|
|
image['bpc'] = pdfimage['/BitsPerComponent']
|
|
if '/Filter' in pdfimage:
|
|
filter_ = pdfimage['/Filter']
|
|
if isinstance(filter_, pypdf.generic.ArrayObject):
|
|
filter_ = filter_[0]
|
|
image['enc'] = FRIENDLY_ENCODING.get(filter_, 'image')
|
|
else:
|
|
image['enc'] = 'image'
|
|
if '/ColorSpace' in pdfimage:
|
|
cs = pdfimage['/ColorSpace']
|
|
if isinstance(cs, pypdf.generic.ArrayObject):
|
|
cs = cs[0]
|
|
image['color'] = FRIENDLY_COLORSPACE.get(cs, '-')
|
|
else:
|
|
image['color'] = 'jpx' if image['enc'] == 'jpx' else '?'
|
|
|
|
image['comp'] = FRIENDLY_COMP.get(image['color'], '?')
|
|
image['dpi_w'] = image['dpi_h'] = 0
|
|
|
|
for raster in contentsinfo.raster_settings:
|
|
# Loop in case the same image is display multiple times on a page
|
|
if raster[0] != image['name']:
|
|
continue
|
|
shorthand = raster[1]
|
|
|
|
dpi_w, dpi_h = _get_dpi(
|
|
shorthand, (image['width'], image['height']))
|
|
|
|
# When image is used multiple times take the highest DPI it is
|
|
# rendered at
|
|
image['dpi_w'] = max(dpi_w, image.get('dpi_w', 0))
|
|
image['dpi_h'] = max(dpi_h, image.get('dpi_h', 0))
|
|
|
|
image['dpi_w'] = Decimal(image['dpi_w'])
|
|
image['dpi_h'] = Decimal(image['dpi_h'])
|
|
image['dpi'] = (image['dpi_w'] * image['dpi_h']) ** Decimal(0.5)
|
|
yield image
|
|
|
|
|
|
def _page_has_text(pdf, page):
|
|
# Simple test
|
|
text = page.extractText()
|
|
if text.strip() != '':
|
|
return True
|
|
|
|
# More nuanced test to deal with quirks of Tesseract PDF generation
|
|
# Check if there's a Glyphless font
|
|
try:
|
|
font = page['/Resources']['/Font']
|
|
except KeyError:
|
|
pass
|
|
else:
|
|
font_objects = list(font.keys())
|
|
for font_object in font_objects:
|
|
basefont = font[font_object]['/BaseFont']
|
|
if basefont.endswith('GlyphLessFont'):
|
|
return True
|
|
|
|
return False
|
|
|
|
|
|
def _pdf_get_pageinfo(infile, pageno: int):
|
|
pageinfo = {}
|
|
pageinfo['pageno'] = pageno
|
|
pageinfo['images'] = []
|
|
|
|
pdf = pypdf.PdfFileReader(infile)
|
|
page = pdf.pages[pageno]
|
|
|
|
pageinfo['has_text'] = _page_has_text(pdf, page)
|
|
|
|
width_pt = page.mediaBox.getWidth()
|
|
height_pt = page.mediaBox.getHeight()
|
|
pageinfo['width_inches'] = width_pt / Decimal(72.0)
|
|
pageinfo['height_inches'] = height_pt / Decimal(72.0)
|
|
|
|
try:
|
|
contentstream = pypdf.pdf.ContentStream(page.getContents(), pdf)
|
|
except AttributeError as e:
|
|
return pageinfo
|
|
|
|
contentsinfo = _interpret_contents(contentstream)
|
|
print(contentsinfo)
|
|
pageinfo['images'] = [im for im in _find_page_images(
|
|
page, pageinfo, contentsinfo)]
|
|
|
|
if pageinfo['images']:
|
|
xres = max(image['dpi_w'] for image in pageinfo['images'])
|
|
yres = max(image['dpi_h'] for image in pageinfo['images'])
|
|
pageinfo['xres'], pageinfo['yres'] = xres, yres
|
|
pageinfo['width_pixels'] = \
|
|
int(round(xres * pageinfo['width_inches']))
|
|
pageinfo['height_pixels'] = \
|
|
int(round(yres * pageinfo['height_inches']))
|
|
|
|
return pageinfo
|
|
|
|
|
|
def pdf_get_all_pageinfo(infile):
|
|
pdf = pypdf.PdfFileReader(infile)
|
|
getcontext().prec = 6
|
|
return [_pdf_get_pageinfo(infile, n) for n in range(pdf.numPages)]
|
|
|
|
|
|
def main():
|
|
import argparse
|
|
parser = argparse.ArgumentParser()
|
|
parser.add_argument('infile')
|
|
args = parser.parse_args()
|
|
info = pdf_get_all_pageinfo(args.infile)
|
|
from pprint import pprint
|
|
pprint(info)
|
|
|
|
|
|
if __name__ == '__main__':
|
|
main()
|