forked from josch/img2pdf
124 lines
4.4 KiB
Python
124 lines
4.4 KiB
Python
#!/usr/bin/env python
|
|
#
|
|
# Copyright (C) 2013 Johannes Schauer Marin Rodrigues <j.schauer at email.de>
|
|
#
|
|
# this module is heavily based upon jpylyzer which is
|
|
# KB / National Library of the Netherlands, Open Planets Foundation
|
|
# and released under the same license conditions
|
|
#
|
|
# This program is free software: you can redistribute it and/or modify
|
|
# it under the terms of the GNU Lesser General Public License as published by
|
|
# the Free Software Foundation, either version 3 of the License, or
|
|
# (at your option) any later version.
|
|
#
|
|
# This program is distributed in the hope that it will be useful,
|
|
# but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
# GNU Lesser General Public License for more details.
|
|
#
|
|
# You should have received a copy of the GNU Lesser General Public License
|
|
# along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
import struct
|
|
|
|
|
|
def getBox(data, byteStart, noBytes):
|
|
boxLengthValue = struct.unpack(">I", data[byteStart : byteStart + 4])[0]
|
|
boxType = data[byteStart + 4 : byteStart + 8]
|
|
contentsStartOffset = 8
|
|
if boxLengthValue == 1:
|
|
boxLengthValue = struct.unpack(">Q", data[byteStart + 8 : byteStart + 16])[0]
|
|
contentsStartOffset = 16
|
|
if boxLengthValue == 0:
|
|
boxLengthValue = noBytes - byteStart
|
|
byteEnd = byteStart + boxLengthValue
|
|
boxContents = data[byteStart + contentsStartOffset : byteEnd]
|
|
return (boxLengthValue, boxType, byteEnd, boxContents)
|
|
|
|
|
|
def parse_ihdr(data):
|
|
height = struct.unpack(">I", data[0:4])[0]
|
|
width = struct.unpack(">I", data[4:8])[0]
|
|
return width, height
|
|
|
|
|
|
def parse_colr(data):
|
|
meth = struct.unpack(">B", data[0:1])[0]
|
|
if meth != 1:
|
|
raise Exception("only enumerated color method supported")
|
|
enumCS = struct.unpack(">I", data[3:])[0]
|
|
if enumCS == 16:
|
|
return "RGB"
|
|
elif enumCS == 17:
|
|
return "L"
|
|
else:
|
|
raise Exception(
|
|
"only sRGB and greyscale color space is supported, " "got %d" % enumCS
|
|
)
|
|
|
|
|
|
def parse_resc(data):
|
|
hnum, hden, vnum, vden, hexp, vexp = struct.unpack(">HHHHBB", data)
|
|
hdpi = ((hnum / hden) * (10 ** hexp) * 100) / 2.54
|
|
vdpi = ((vnum / vden) * (10 ** vexp) * 100) / 2.54
|
|
return hdpi, vdpi
|
|
|
|
|
|
def parse_res(data):
|
|
hdpi, vdpi = None, None
|
|
noBytes = len(data)
|
|
byteStart = 0
|
|
boxLengthValue = 1 # dummy value for while loop condition
|
|
while byteStart < noBytes and boxLengthValue != 0:
|
|
boxLengthValue, boxType, byteEnd, boxContents = getBox(data, byteStart, noBytes)
|
|
if boxType == b"resc":
|
|
hdpi, vdpi = parse_resc(boxContents)
|
|
break
|
|
return hdpi, vdpi
|
|
|
|
|
|
def parse_jp2h(data):
|
|
width, height, colorspace, hdpi, vdpi = None, None, None, None, None
|
|
noBytes = len(data)
|
|
byteStart = 0
|
|
boxLengthValue = 1 # dummy value for while loop condition
|
|
while byteStart < noBytes and boxLengthValue != 0:
|
|
boxLengthValue, boxType, byteEnd, boxContents = getBox(data, byteStart, noBytes)
|
|
if boxType == b"ihdr":
|
|
width, height = parse_ihdr(boxContents)
|
|
elif boxType == b"colr":
|
|
colorspace = parse_colr(boxContents)
|
|
elif boxType == b"res ":
|
|
hdpi, vdpi = parse_res(boxContents)
|
|
byteStart = byteEnd
|
|
return (width, height, colorspace, hdpi, vdpi)
|
|
|
|
|
|
def parsejp2(data):
|
|
noBytes = len(data)
|
|
byteStart = 0
|
|
boxLengthValue = 1 # dummy value for while loop condition
|
|
width, height, colorspace, hdpi, vdpi = None, None, None, None, None
|
|
while byteStart < noBytes and boxLengthValue != 0:
|
|
boxLengthValue, boxType, byteEnd, boxContents = getBox(data, byteStart, noBytes)
|
|
if boxType == b"jp2h":
|
|
width, height, colorspace, hdpi, vdpi = parse_jp2h(boxContents)
|
|
break
|
|
byteStart = byteEnd
|
|
if not width:
|
|
raise Exception("no width in jp2 header")
|
|
if not height:
|
|
raise Exception("no height in jp2 header")
|
|
if not colorspace:
|
|
raise Exception("no colorspace in jp2 header")
|
|
# retrieving the dpi is optional so we do not error out if not present
|
|
return (width, height, colorspace, hdpi, vdpi)
|
|
|
|
|
|
if __name__ == "__main__":
|
|
import sys
|
|
|
|
width, height, colorspace = parsejp2(open(sys.argv[1]).read())
|
|
sys.stdout.write("width = %d" % width)
|
|
sys.stdout.write("height = %d" % height)
|
|
sys.stdout.write("colorspace = %s" % colorspace)
|