forked from josch/img2pdf
read horizontal and vertical dpi from jpeg2000 files
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parent
ef9eac7326
commit
e5b0ffee6c
1 changed files with 30 additions and 7 deletions
37
src/jp2.py
37
src/jp2.py
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@ -56,8 +56,29 @@ def parse_colr(data):
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"got %d" % enumCS)
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def parse_resc(data):
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hnum, hden, vnum, vden, hexp, vexp = struct.unpack(">HHHHBB", data)
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hdpi = ((hnum/hden) * (10**hexp) * 100)/2.54
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vdpi = ((vnum/vden) * (10**vexp) * 100)/2.54
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return hdpi, vdpi
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def parse_res(data):
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hdpi, vdpi = 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 = \
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getBox(data, byteStart, noBytes)
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if boxType == b'resc':
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hdpi, vdpi = parse_resc(boxContents)
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break
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return hdpi, vdpi
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def parse_jp2h(data):
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width, height, colorspace = None, None, None
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width, height, colorspace, hdpi, vdpi = None, None, 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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@ -68,22 +89,23 @@ def parse_jp2h(data):
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width, height = parse_ihdr(boxContents)
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elif boxType == b'colr':
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colorspace = parse_colr(boxContents)
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elif boxType == b'res ':
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hdpi, vdpi = parse_res(boxContents)
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byteStart = byteEnd
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return (width, height, colorspace)
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return (width, height, colorspace, hdpi, vdpi)
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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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width = None
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height = None
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colorspace = None
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width, height, colorspace, hdpi, vdpi = None, None, None, None, None
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while byteStart < noBytes and boxLengthValue != 0:
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boxLengthValue, boxType, byteEnd, boxContents = \
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getBox(data, byteStart, noBytes)
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if boxType == b'jp2h':
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width, height, colorspace = parse_jp2h(boxContents)
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width, height, colorspace, hdpi, vdpi = parse_jp2h(boxContents)
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break
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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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@ -91,7 +113,8 @@ def parsejp2(data):
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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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# retrieving the dpi is optional so we do not error out if not present
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return (width, height, colorspace, hdpi, vdpi)
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if __name__ == "__main__":
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import sys
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