122 строки
3.2 KiB
Plaintext
122 строки
3.2 KiB
Plaintext
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#!/usr/bin/env python
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# $URL: http://pypng.googlecode.com/svn/trunk/code/pipcomposite $
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# $Rev: 208 $
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# pipcomposite
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# Image alpha compositing.
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"""
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pipcomposite [--background #rrggbb] file.png
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Composite an image onto a background and output the result. The
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background colour is specified with an HTML-style triple (3, 6, or 12
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hex digits), and defaults to black (#000).
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The output PNG has no alpha channel.
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It is valid for the input to have no alpha channel, but it doesn't
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make much sense: the output will equal the input.
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"""
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import sys
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def composite(out, inp, background):
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import png
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p = png.Reader(file=inp)
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w,h,pixel,info = p.asRGBA()
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outinfo = dict(info)
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outinfo['alpha'] = False
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outinfo['planes'] -= 1
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outinfo['interlace'] = 0
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# Convert to tuple and normalise to same range as source.
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background = rgbhex(background)
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maxval = float(2**info['bitdepth'] - 1)
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background = map(lambda x: int(0.5 + x*maxval/65535.0),
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background)
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# Repeat background so that it's a whole row of sample values.
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background *= w
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def iterrow():
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for row in pixel:
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# Remove alpha from row, then create a list with one alpha
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# entry _per channel value_.
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# Squirrel the alpha channel away (and normalise it).
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t = map(lambda x: x/maxval, row[3::4])
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row = list(row)
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del row[3::4]
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alpha = row[:]
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for i in range(3):
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alpha[i::3] = t
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assert len(alpha) == len(row) == len(background)
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yield map(lambda a,v,b: int(0.5 + a*v + (1.0-a)*b),
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alpha, row, background)
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w = png.Writer(**outinfo)
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w.write(out, iterrow())
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def rgbhex(s):
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"""Take an HTML style string of the form "#rrggbb" and return a
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colour (R,G,B) triple. Following the initial '#' there can be 3, 6,
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or 12 digits (for 4-, 8- or 16- bits per channel). In all cases the
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values are expanded to a full 16-bit range, so the returned values
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are all in range(65536).
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"""
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assert s[0] == '#'
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s = s[1:]
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assert len(s) in (3,6,12)
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# Create a target list of length 12, and expand the string s to make
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# it length 12.
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l = ['z']*12
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if len(s) == 3:
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for i in range(4):
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l[i::4] = s
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if len(s) == 6:
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for i in range(2):
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l[i::4] = s[i::2]
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l[i+2::4] = s[i::2]
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if len(s) == 12:
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l[:] = s
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s = ''.join(l)
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return map(lambda x: int(x, 16), (s[:4], s[4:8], s[8:]))
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class Usage(Exception):
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pass
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def main(argv=None):
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import getopt
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import sys
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if argv is None:
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argv = sys.argv
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argv = argv[1:]
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try:
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try:
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opt,arg = getopt.getopt(argv, '',
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['background='])
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except getopt.error, msg:
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raise Usage(msg)
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background = '#000'
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for o,v in opt:
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if o in ['--background']:
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background = v
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except Usage, err:
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print >>sys.stderr, __doc__
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print >>sys.stderr, str(err)
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return 2
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if len(arg) > 0:
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f = open(arg[0], 'rb')
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else:
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f = sys.stdin
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return composite(sys.stdout, f, background)
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if __name__ == '__main__':
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main()
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