source: subversion/applications/routing/pyroute/colorsys.py

Last change on this file was 5892, checked in by ojw, 12 years ago

Apparently colorsys isn't available on lots of places (e.g. openmoko),
so adding a copy to get distrubuted with pyroute

File size: 3.4 KB
Line 
1"""Conversion functions between RGB and other color systems.
2
3This modules provides two functions for each color system ABC:
4
5  rgb_to_abc(r, g, b) --> a, b, c
6  abc_to_rgb(a, b, c) --> r, g, b
7
8All inputs and outputs are triples of floats in the range [0.0...1.0]
9(with the exception of I and Q, which covers a slightly larger range).
10Inputs outside the valid range may cause exceptions or invalid outputs.
11
12Supported color systems:
13RGB: Red, Green, Blue components
14YIQ: Luminance, Chrominance (used by composite video signals)
15HLS: Hue, Luminance, Saturation
16HSV: Hue, Saturation, Value
17"""
18
19# References:
20# http://en.wikipedia.org/wiki/YIQ
21# http://en.wikipedia.org/wiki/HLS_color_space
22# http://en.wikipedia.org/wiki/HSV_color_space
23
24__all__ = ["rgb_to_yiq","yiq_to_rgb","rgb_to_hls","hls_to_rgb",
25           "rgb_to_hsv","hsv_to_rgb"]
26
27# Some floating point constants
28
29ONE_THIRD = 1.0/3.0
30ONE_SIXTH = 1.0/6.0
31TWO_THIRD = 2.0/3.0
32
33# YIQ: used by composite video signals (linear combinations of RGB)
34# Y: perceived grey level (0.0 == black, 1.0 == white)
35# I, Q: color components
36
37def rgb_to_yiq(r, g, b):
38    y = 0.30*r + 0.59*g + 0.11*b
39    i = 0.60*r - 0.28*g - 0.32*b
40    q = 0.21*r - 0.52*g + 0.31*b
41    return (y, i, q)
42
43def yiq_to_rgb(y, i, q):
44    r = y + 0.948262*i + 0.624013*q
45    g = y - 0.276066*i - 0.639810*q
46    b = y - 1.105450*i + 1.729860*q
47    if r < 0.0: r = 0.0
48    if g < 0.0: g = 0.0
49    if b < 0.0: b = 0.0
50    if r > 1.0: r = 1.0
51    if g > 1.0: g = 1.0
52    if b > 1.0: b = 1.0
53    return (r, g, b)
54
55
56# HLS: Hue, Luminance, Saturation
57# H: position in the spectrum
58# L: color lightness
59# S: color saturation
60
61def rgb_to_hls(r, g, b):
62    maxc = max(r, g, b)
63    minc = min(r, g, b)
64    # XXX Can optimize (maxc+minc) and (maxc-minc)
65    l = (minc+maxc)/2.0
66    if minc == maxc: return 0.0, l, 0.0
67    if l <= 0.5: s = (maxc-minc) / (maxc+minc)
68    else: s = (maxc-minc) / (2.0-maxc-minc)
69    rc = (maxc-r) / (maxc-minc)
70    gc = (maxc-g) / (maxc-minc)
71    bc = (maxc-b) / (maxc-minc)
72    if r == maxc: h = bc-gc
73    elif g == maxc: h = 2.0+rc-bc
74    else: h = 4.0+gc-rc
75    h = (h/6.0) % 1.0
76    return h, l, s
77
78def hls_to_rgb(h, l, s):
79    if s == 0.0: return l, l, l
80    if l <= 0.5: m2 = l * (1.0+s)
81    else: m2 = l+s-(l*s)
82    m1 = 2.0*l - m2
83    return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD))
84
85def _v(m1, m2, hue):
86    hue = hue % 1.0
87    if hue < ONE_SIXTH: return m1 + (m2-m1)*hue*6.0
88    if hue < 0.5: return m2
89    if hue < TWO_THIRD: return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0
90    return m1
91
92
93# HSV: Hue, Saturation, Value
94# H: position in the spectrum
95# S: color saturation ("purity")
96# V: color brightness
97
98def rgb_to_hsv(r, g, b):
99    maxc = max(r, g, b)
100    minc = min(r, g, b)
101    v = maxc
102    if minc == maxc: return 0.0, 0.0, v
103    s = (maxc-minc) / maxc
104    rc = (maxc-r) / (maxc-minc)
105    gc = (maxc-g) / (maxc-minc)
106    bc = (maxc-b) / (maxc-minc)
107    if r == maxc: h = bc-gc
108    elif g == maxc: h = 2.0+rc-bc
109    else: h = 4.0+gc-rc
110    h = (h/6.0) % 1.0
111    return h, s, v
112
113def hsv_to_rgb(h, s, v):
114    if s == 0.0: return v, v, v
115    i = int(h*6.0) # XXX assume int() truncates!
116    f = (h*6.0) - i
117    p = v*(1.0 - s)
118    q = v*(1.0 - s*f)
119    t = v*(1.0 - s*(1.0-f))
120    if i%6 == 0: return v, t, p
121    if i == 1: return q, v, p
122    if i == 2: return p, v, t
123    if i == 3: return p, q, v
124    if i == 4: return t, p, v
125    if i == 5: return v, p, q
126    # Cannot get here
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