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