mirror of
https://github.com/python/cpython.git
synced 2025-10-31 21:51:50 +00:00
e99d5ea25b
added test script and expected output file as well this closes patch 103297. __all__ attributes will be added to other modules without first submitting a patch, just adding the necessary line to the test script to verify more-or-less correct implementation.
123 lines
3.1 KiB
Python
123 lines
3.1 KiB
Python
"""Conversion functions between RGB and other color systems.
|
|
|
|
This modules provides two functions for each color system ABC:
|
|
|
|
rgb_to_abc(r, g, b) --> a, b, c
|
|
abc_to_rgb(a, b, c) --> r, g, b
|
|
|
|
All inputs and outputs are triples of floats in the range [0.0...1.0].
|
|
Inputs outside this range may cause exceptions or invalid outputs.
|
|
|
|
Supported color systems:
|
|
RGB: Red, Green, Blue components
|
|
YIQ: used by composite video signals
|
|
HLS: Hue, Luminance, Saturation
|
|
HSV: Hue, Saturation, Value
|
|
"""
|
|
# References:
|
|
# XXX Where's the literature?
|
|
|
|
__all__ = ["rgb_to_yiq","yiq_to_rgb","rgb_to_hls","hls_to_rgb",
|
|
"rgb_to_hsv","hsv_to_rgb"]
|
|
|
|
# Some floating point constants
|
|
|
|
ONE_THIRD = 1.0/3.0
|
|
ONE_SIXTH = 1.0/6.0
|
|
TWO_THIRD = 2.0/3.0
|
|
|
|
|
|
# YIQ: used by composite video signals (linear combinations of RGB)
|
|
# Y: perceived grey level (0.0 == black, 1.0 == white)
|
|
# I, Q: color components
|
|
|
|
def rgb_to_yiq(r, g, b):
|
|
y = 0.30*r + 0.59*g + 0.11*b
|
|
i = 0.60*r - 0.28*g - 0.32*b
|
|
q = 0.21*r - 0.52*g + 0.31*b
|
|
return (y, i, q)
|
|
|
|
def yiq_to_rgb(y, i, q):
|
|
r = y + 0.948262*i + 0.624013*q
|
|
g = y - 0.276066*i - 0.639810*q
|
|
b = y - 1.105450*i + 1.729860*q
|
|
if r < 0.0: r = 0.0
|
|
if g < 0.0: g = 0.0
|
|
if b < 0.0: b = 0.0
|
|
if r > 1.0: r = 1.0
|
|
if g > 1.0: g = 1.0
|
|
if b > 1.0: b = 1.0
|
|
return (r, g, b)
|
|
|
|
|
|
# HLS: Hue, Luminance, S???
|
|
# H: position in the spectrum
|
|
# L: ???
|
|
# S: ???
|
|
|
|
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: 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
|
|
|
|
def hls_to_rgb(h, l, s):
|
|
if s == 0.0: return l, l, l
|
|
if l <= 0.5: m2 = l * (1.0+s)
|
|
else: m2 = l+s-(l*s)
|
|
m1 = 2.0*l - m2
|
|
return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD))
|
|
|
|
def _v(m1, m2, hue):
|
|
hue = hue % 1.0
|
|
if hue < ONE_SIXTH: return m1 + (m2-m1)*hue*6.0
|
|
if hue < 0.5: return m2
|
|
if hue < TWO_THIRD: return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0
|
|
return m1
|
|
|
|
|
|
# HSV: Hue, Saturation, Value(?)
|
|
# H: position in the spectrum
|
|
# S: ???
|
|
# V: ???
|
|
|
|
def rgb_to_hsv(r, g, b):
|
|
maxc = max(r, g, b)
|
|
minc = min(r, g, b)
|
|
v = maxc
|
|
if minc == maxc: return 0.0, 0.0, v
|
|
s = (maxc-minc) / maxc
|
|
rc = (maxc-r) / (maxc-minc)
|
|
gc = (maxc-g) / (maxc-minc)
|
|
bc = (maxc-b) / (maxc-minc)
|
|
if r == maxc: 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, s, v
|
|
|
|
def hsv_to_rgb(h, s, v):
|
|
if s == 0.0: return v, v, v
|
|
i = int(h*6.0) # XXX assume int() truncates!
|
|
f = (h*6.0) - i
|
|
p = v*(1.0 - s)
|
|
q = v*(1.0 - s*f)
|
|
t = v*(1.0 - s*(1.0-f))
|
|
if i%6 == 0: return v, t, p
|
|
if i == 1: return q, v, p
|
|
if i == 2: return p, v, t
|
|
if i == 3: return p, q, v
|
|
if i == 4: return t, p, v
|
|
if i == 5: return v, p, q
|
|
# Cannot get here
|