Issue #1515: Enable use of deepcopy() with instance methods. Patch by Robert Collins.
[python.git] / Lib / colorsys.py
bloba6c0cf6a4639e73e3aee9d66a52619d74dfb0d45
1 """Conversion functions between RGB and other color systems.
3 This modules provides two functions for each color system ABC:
5 rgb_to_abc(r, g, b) --> a, b, c
6 abc_to_rgb(a, b, c) --> r, g, b
8 All 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).
10 Inputs outside the valid range may cause exceptions or invalid outputs.
12 Supported color systems:
13 RGB: Red, Green, Blue components
14 YIQ: Luminance, Chrominance (used by composite video signals)
15 HLS: Hue, Luminance, Saturation
16 HSV: Hue, Saturation, Value
17 """
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
24 __all__ = ["rgb_to_yiq","yiq_to_rgb","rgb_to_hls","hls_to_rgb",
25 "rgb_to_hsv","hsv_to_rgb"]
27 # Some floating point constants
29 ONE_THIRD = 1.0/3.0
30 ONE_SIXTH = 1.0/6.0
31 TWO_THIRD = 2.0/3.0
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
37 def 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)
43 def 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:
48 r = 0.0
49 if g < 0.0:
50 g = 0.0
51 if b < 0.0:
52 b = 0.0
53 if r > 1.0:
54 r = 1.0
55 if g > 1.0:
56 g = 1.0
57 if b > 1.0:
58 b = 1.0
59 return (r, g, b)
62 # HLS: Hue, Luminance, Saturation
63 # H: position in the spectrum
64 # L: color lightness
65 # S: color saturation
67 def rgb_to_hls(r, g, b):
68 maxc = max(r, g, b)
69 minc = min(r, g, b)
70 # XXX Can optimize (maxc+minc) and (maxc-minc)
71 l = (minc+maxc)/2.0
72 if minc == maxc:
73 return 0.0, l, 0.0
74 if l <= 0.5:
75 s = (maxc-minc) / (maxc+minc)
76 else:
77 s = (maxc-minc) / (2.0-maxc-minc)
78 rc = (maxc-r) / (maxc-minc)
79 gc = (maxc-g) / (maxc-minc)
80 bc = (maxc-b) / (maxc-minc)
81 if r == maxc:
82 h = bc-gc
83 elif g == maxc:
84 h = 2.0+rc-bc
85 else:
86 h = 4.0+gc-rc
87 h = (h/6.0) % 1.0
88 return h, l, s
90 def hls_to_rgb(h, l, s):
91 if s == 0.0:
92 return l, l, l
93 if l <= 0.5:
94 m2 = l * (1.0+s)
95 else:
96 m2 = l+s-(l*s)
97 m1 = 2.0*l - m2
98 return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD))
100 def _v(m1, m2, hue):
101 hue = hue % 1.0
102 if hue < ONE_SIXTH:
103 return m1 + (m2-m1)*hue*6.0
104 if hue < 0.5:
105 return m2
106 if hue < TWO_THIRD:
107 return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0
108 return m1
111 # HSV: Hue, Saturation, Value
112 # H: position in the spectrum
113 # S: color saturation ("purity")
114 # V: color brightness
116 def rgb_to_hsv(r, g, b):
117 maxc = max(r, g, b)
118 minc = min(r, g, b)
119 v = maxc
120 if minc == maxc:
121 return 0.0, 0.0, v
122 s = (maxc-minc) / maxc
123 rc = (maxc-r) / (maxc-minc)
124 gc = (maxc-g) / (maxc-minc)
125 bc = (maxc-b) / (maxc-minc)
126 if r == maxc:
127 h = bc-gc
128 elif g == maxc:
129 h = 2.0+rc-bc
130 else:
131 h = 4.0+gc-rc
132 h = (h/6.0) % 1.0
133 return h, s, v
135 def hsv_to_rgb(h, s, v):
136 if s == 0.0:
137 return v, v, v
138 i = int(h*6.0) # XXX assume int() truncates!
139 f = (h*6.0) - i
140 p = v*(1.0 - s)
141 q = v*(1.0 - s*f)
142 t = v*(1.0 - s*(1.0-f))
143 i = i%6
144 if i == 0:
145 return v, t, p
146 if i == 1:
147 return q, v, p
148 if i == 2:
149 return p, v, t
150 if i == 3:
151 return p, q, v
152 if i == 4:
153 return t, p, v
154 if i == 5:
155 return v, p, q
156 # Cannot get here