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gh-106498: Fix an extreme case in colorsys.rgb_to_hls #106530

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gh-106498: Fix an extreme case in colorsys.rgb_to_hls #106530

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7b106c3
Add fix and regression test for near white color
gaogaotiantian Jul 7, 2023
c02bdb1
📜🤖 Added by blurb_it.
blurb-it[bot] Jul 7, 2023
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8 changes: 7 additions & 1 deletion Lib/colorsys.py
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,13 @@ def rgb_to_hls(r, g, b):
sumc = (maxc+minc)
rangec = (maxc-minc)
l = sumc/2.0
if minc == maxc:
# gh-106498
# Due to a degree of float precision error, it's possible that maxc != minc
# but maxc + minc == 2.0. Which will make (2.0 - sumc) zero, causing the
# ZeroDivisionError.
# e.g. colorsys.rgb_to_hls(1, 1, 0.9999999999999999)
# In this case, it's an extreme near white color so we can just return white
if minc == maxc or sumc == 2.0:
return 0.0, l, 0.0
if l <= 0.5:
s = rangec / sumc
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6 changes: 6 additions & 0 deletions Lib/test/test_colorsys.py
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Expand Up @@ -69,6 +69,12 @@ def test_hls_values(self):
self.assertTripleEqual(hls, colorsys.rgb_to_hls(*rgb))
self.assertTripleEqual(rgb, colorsys.hls_to_rgb(*hls))

def test_hls_corner_case(self):
try:
colorsys.rgb_to_hls(1, 1, 0.9999999999999999)
except Exception:
self.fail("rgb_to_hls(1, 1, 0.9999999999999999) raised an exception!")

def test_yiq_roundtrip(self):
for r in frange(0.0, 1.0, 0.2):
for g in frange(0.0, 1.0, 0.2):
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2023-07-07-19-46-27.gh-issue-106498.ijJ-eH.rst
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@@ -0,0 +1 @@
Fixed :func:`colorsys.rgb_to_hls` under an extreme input.
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