mirror of https://github.com/python/cpython.git
166 lines
3.9 KiB
Python
166 lines
3.9 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]
|
|
(with the exception of I and Q, which covers a slightly larger range).
|
|
Inputs outside the valid range may cause exceptions or invalid outputs.
|
|
|
|
Supported color systems:
|
|
RGB: Red, Green, Blue components
|
|
YIQ: Luminance, Chrominance (used by composite video signals)
|
|
HLS: Hue, Luminance, Saturation
|
|
HSV: Hue, Saturation, Value
|
|
"""
|
|
|
|
# References:
|
|
# http://en.wikipedia.org/wiki/YIQ
|
|
# http://en.wikipedia.org/wiki/HLS_color_space
|
|
# http://en.wikipedia.org/wiki/HSV_color_space
|
|
|
|
__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
|
|
#
|
|
# There are a great many versions of the constants used in these formulae.
|
|
# The ones in this library uses constants from the FCC version of NTSC.
|
|
|
|
def rgb_to_yiq(r, g, b):
|
|
y = 0.30*r + 0.59*g + 0.11*b
|
|
i = 0.74*(r-y) - 0.27*(b-y)
|
|
q = 0.48*(r-y) + 0.41*(b-y)
|
|
return (y, i, q)
|
|
|
|
def yiq_to_rgb(y, i, q):
|
|
# r = y + (0.27*q + 0.41*i) / (0.74*0.41 + 0.27*0.48)
|
|
# b = y + (0.74*q - 0.48*i) / (0.74*0.41 + 0.27*0.48)
|
|
# g = y - (0.30*(r-y) + 0.11*(b-y)) / 0.59
|
|
|
|
r = y + 0.9468822170900693*i + 0.6235565819861433*q
|
|
g = y - 0.27478764629897834*i - 0.6356910791873801*q
|
|
b = y - 1.1085450346420322*i + 1.7090069284064666*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, Saturation
|
|
# H: position in the spectrum
|
|
# L: color lightness
|
|
# S: color saturation
|
|
|
|
def rgb_to_hls(r, g, b):
|
|
maxc = max(r, g, b)
|
|
minc = min(r, g, b)
|
|
sumc = (maxc+minc)
|
|
rangec = (maxc-minc)
|
|
l = sumc/2.0
|
|
if minc == maxc:
|
|
return 0.0, l, 0.0
|
|
if l <= 0.5:
|
|
s = rangec / sumc
|
|
else:
|
|
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:
|
|
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: color saturation ("purity")
|
|
# V: color brightness
|
|
|
|
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))
|
|
i = i%6
|
|
if i == 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
|