bpo-42452: Improve colorsys.rgb_to_hls code (GH-23306)
Cache repeated sum and difference to make code slightly faster and easier to read.
diff --git a/Lib/colorsys.py b/Lib/colorsys.py
index b93e384..0f52512 100644
--- a/Lib/colorsys.py
+++ b/Lib/colorsys.py
@@ -75,17 +75,18 @@ def yiq_to_rgb(y, i, q):
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
+ sumc = (maxc+minc)
+ rangec = (maxc-minc)
+ l = sumc/2.0
if minc == maxc:
return 0.0, l, 0.0
if l <= 0.5:
- s = (maxc-minc) / (maxc+minc)
+ s = rangec / sumc
else:
- s = (maxc-minc) / (2.0-maxc-minc)
- rc = (maxc-r) / (maxc-minc)
- gc = (maxc-g) / (maxc-minc)
- bc = (maxc-b) / (maxc-minc)
+ s = rangec / (2.0-sumc)
+ rc = (maxc-r) / rangec
+ gc = (maxc-g) / rangec
+ bc = (maxc-b) / rangec
if r == maxc:
h = bc-gc
elif g == maxc: