New submission from Mats Luspa:
In the colorsys library function rgb_to_hls the algorithm is not implemented
quite correctly.
According to algorithm the correct implementation should be (the error is in
the condition r == maxc). In the current code g<b is not tested:
def rgb_to_hls(r, g, b):
maxc = max(r, g, b)
minc = min(r, g, b)
# XXX Can optimize (maxc+minc) and (maxc-minc)
l = (minc+maxc)/2.0
if minc == maxc:
return 0.0, l, 0.0
if l <= 0.5:
s = (maxc-minc) / (maxc+minc)
else:
s = (maxc-minc) / (2.0-maxc-minc)
rc = (maxc-r) / (maxc-minc)
gc = (maxc-g) / (maxc-minc)
bc = (maxc-b) / (maxc-minc)
if r == maxc:
if (g<b):
h = bc-gc+6
else:
h = bc-gc
elif g == maxc:
h = 2.0+rc-bc
else:
h = 4.0+gc-rc
h = (h/6.0) % 1.0
return h, l, s
----------
components: Library (Lib)
messages: 259659
nosy: Mats Luspa
priority: normal
severity: normal
status: open
title: colorys rgb_to_hls algorithm error
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue26296>
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