diff options
author | Johannes Schauer <josch@debian.org> | 2016-08-16 16:35:49 +0200 |
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committer | Johannes Schauer <josch@debian.org> | 2016-08-16 16:35:49 +0200 |
commit | 65960d846bed2bbc1a83269b715bb78e83e36478 (patch) | |
tree | 49728d11d3f9269ad1856c1eaaf32b6a4a933028 /src/jp2.py |
Import img2pdf_0.2.1.orig.tar.gz
[dgit import orig img2pdf_0.2.1.orig.tar.gz]
Diffstat (limited to 'src/jp2.py')
-rw-r--r-- | src/jp2.py | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/src/jp2.py b/src/jp2.py new file mode 100644 index 0000000..7f61312 --- /dev/null +++ b/src/jp2.py @@ -0,0 +1,124 @@ +#!/usr/bin/env python +# +# Copyright (C) 2013 Johannes 'josch' Schauer <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) |