Optimise ImageColor using functools.lru_cache

[hugovk]

Follow on from #7632, use functools.lru_cache to cache the computed colours of ImageColor.getrgb(color) and ImageColor.getcolor(color, mode).

getrgb

Running these:

python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('red')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('#defdef')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('#00f')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('rgb(0,255,0)')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('rgba(255,0,0,0)')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('hsl(0.1,99.2%,50.3%)')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('hsv(360.,100.0%,100%)')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('HSB(0,100%,50%)')"

# all of them:
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getrgb('red'); ImageColor.getrgb('#defdef'); ImageColor.getrgb('#00f'); ImageColor.getrgb('rgb(0,255,0)'); ImageColor.getrgb('rgba(255,0,0,0)'); ImageColor.getrgb('hsl(0.1,99.2%,50.3%)'); ImageColor.getrgb('hsv(360.,100.0%,100%)'); ImageColor.getrgb('HSB(0,100%,50%)')"

Gives an improvement of 3.1 - 91.4 times faster:

color	main	lru_cache	times faster
red	5000000 loops, best of 5: 0.0872 usec per loop	10000000 loops, best of 5: 0.0285 usec per loop	3.1
#defdef	200000 loops, best of 5: 1.05 usec per loop	10000000 loops, best of 5: 0.0288 usec per loop	36.5
#00f	500000 loops, best of 5: 0.575 usec per loop	10000000 loops, best of 5: 0.0287 usec per loop	20.0
rgb(0,255,0)	200000 loops, best of 5: 1.53 usec per loop	10000000 loops, best of 5: 0.029 usec per loop	52.8
rgba(255,0,0,0)	100000 loops, best of 5: 2.46 usec per loop	10000000 loops, best of 5: 0.029 usec per loop	84.8
hsl(0.1,99.2%,50.3%)	100000 loops, best of 5: 2.56 usec per loop	10000000 loops, best of 5: 0.0288 usec per loop	88.9
hsv(360.,100.0%,100%)	100000 loops, best of 5: 2.68 usec per loop	10000000 loops, best of 5: 0.029 usec per loop	92.4
HSB(0,100%,50%)	100000 loops, best of 5: 2.66 usec per loop	10000000 loops, best of 5: 0.029 usec per loop	91.7
all of them	20000 loops, best of 5: 14.3 usec per loop	1000000 loops, best of 5: 0.221 usec per loop	64.7

getcolor

Running these:

python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getcolor('red', 'RGB')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getcolor('red', 'RGBA')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getcolor('red', 'L')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getcolor('red', 'LA')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getcolor('red', '1')"
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getcolor('red', 'HSV')"

# all of them:
python3 -m timeit --unit usec -s "from PIL import ImageColor" "ImageColor.getcolor('red', 'RGB'); ImageColor.getcolor('red', 'RGBA'); ImageColor.getcolor('red', 'L'); ImageColor.getcolor('red', 'LA'); ImageColor.getcolor('red', '1'); ImageColor.getcolor('red', 'HSV')"

Gives an improvement of 5.1 - 19.6 times faster:

mode	main	lru_cache	times faster
RGB	1000000 loops, best of 5: 0.21 usec per loop	10000000 loops, best of 5: 0.0386 usec per loop	5.4
RGBA	1000000 loops, best of 5: 0.232 usec per loop	10000000 loops, best of 5: 0.0381 usec per loop	6.1
L	1000000 loops, best of 5: 0.28 usec per loop	10000000 loops, best of 5: 0.0381 usec per loop	7.3
LA	1000000 loops, best of 5: 0.292 usec per loop	10000000 loops, best of 5: 0.0388 usec per loop	7.5
1	1000000 loops, best of 5: 0.28 usec per loop	10000000 loops, best of 5: 0.038 usec per loop	7.4
HSV	500000 loops, best of 5: 0.761 usec per loop	10000000 loops, best of 5: 0.0389 usec per loop	19.6
all of them	100000 loops, best of 5: 2.16 usec per loop	1000000 loops, best of 5: 0.261 usec per loop	8.3