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#!/usr/bin/env python
# $URL: http://pypng.googlecode.com/svn/trunk/code/pipcolours $
# $Rev: 96 $
# pipcolours - extract all colours present in source image.
def colours(out, inp):
import itertools
import png
r = png.Reader(file=inp)
_,_,pixels,info = r.asDirect()
planes = info['planes']
col = set()
for row in pixels:
# Ewgh, side effects on col
map(col.add, png.group(row, planes))
col,planes = channel_reduce(col, planes)
col = list(col)
col.sort()
col = list(itertools.chain(*col))
width = len(col)//planes
greyscale = planes in (1,2)
alpha = planes in (2,4)
bitdepth = info['bitdepth']
w = png.Writer(width, 1,
bitdepth=bitdepth, greyscale=greyscale, alpha=alpha)
w.write(out, [col])
def channel_reduce(col, planes):
"""Attempt to reduce the number of channels in the set of
colours."""
if planes >= 3:
def isgrey(c):
return c[0] == c[1] == c[2]
if min(map(isgrey, col)) == True:
# Every colour is grey.
col = set(map(lambda x: x[0::3], col))
planes -= 2
return col,planes
def main(argv=None):
import sys
if argv is None:
argv = sys.argv
argv = argv[1:]
if len(argv) > 0:
f = open(argv[0], 'rb')
else:
f = sys.stdin
return colours(sys.stdout, f)
if __name__ == '__main__':
main()
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