Mercurial > cpython-lru_cache-weakref

annotate Lib/colorsys.py @ 5817:48b94de85bf3 legacy-trunk

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Extensive changes by AMK.
author Guido van Rossum <guido@python.org>
date Thu, 17 Jul 1997 16:29:42 +0000
parents 5fb3f73a627f
children b648f9e8b3ed
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5fb3f73a627f New module 'colorsys' implements conversions between different color systems.
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1 # Conversion functions between RGB and other color systems.
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2 #
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3 # Define two functions for each color system XYZ:
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4 # rgb_to_xyz(r, g, b) --> x, y, z
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5 # xyz_to_rgb(x, y, z) --> r, g, b
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6 # All inputs and outputs are triples of floats in the range [0.0...1.0].
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7 # Inputs outside this range may cause exceptions or invalid outputs.
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8 #
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9 # Supported color systems:
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10 # RGB: Red, Green, Blue components
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11 # YIQ: used by composite video signals
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12 # HLS: Hue, Luminance, S???
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13 # HSV: Hue, Saturation, Value(?)
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14 #
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15 # References:
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16 # XXX Where's the literature?
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17
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18
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19 # Some floating point constants
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20
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21 ONE_THIRD = 1.0/3.0
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22 ONE_SIXTH = 1.0/6.0
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23 TWO_THIRD = 2.0/3.0
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24
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25
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26 # YIQ: used by composite video signals (linear combinations of RGB)
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27 # Y: perceived grey level (0.0 == black, 1.0 == white)
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28 # I, Q: color components
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29
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30 def rgb_to_yiq(r, g, b):
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31 y = 0.30*r + 0.59*g + 0.11*b
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32 i = 0.60*r - 0.28*g - 0.32*b
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33 q = 0.21*r - 0.52*g + 0.31*b
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34 return (y, i, q)
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35
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36 def yiq_to_rgb(y, i, q):
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37 r = y + 0.948262*i + 0.624013*q
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38 g = y - 0.276066*i - 0.639810*q
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39 b = y - 1.105450*i + 1.729860*q
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40 if r < 0.0: r = 0.0
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41 if g < 0.0: g = 0.0
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42 if b < 0.0: b = 0.0
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43 if r > 1.0: r = 1.0
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44 if g > 1.0: g = 1.0
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45 if b > 1.0: b = 1.0
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46 return (r, g, b)
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47
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48
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49 # HLS: Hue, Luminance, S???
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50 # H: position in the spectrum
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51 # L: ???
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52 # S: ???
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53
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54 def rgb_to_hls(r, g, b):
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55 maxc = max(r, g, b)
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56 minc = min(r, g, b)
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57 # XXX Can optimize (maxc+minc) and (maxc-minc)
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58 l = (minc+maxc)/2.0
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59 if minc == maxc: return 0.0, l, 0.0
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60 if l <= 0.5: s = (maxc-minc) / (maxc+minc)
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61 else: s = (maxc-minc) / (2.0-maxc-minc)
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62 rc = (maxc-r) / (maxc-minc)
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63 gc = (maxc-g) / (maxc-minc)
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64 bc = (maxc-b) / (maxc-minc)
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65 if r == maxc: h = bc-gc
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66 elif g == maxc: h = 2.0+rc-bc
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67 else: h = 4.0+gc-rc
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68 h = (h/6.0) % 1.0
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69 return h, l, s
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70
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71 def hls_to_rgb(h, l, s):
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72 if s == 0.0: return l, l, l
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73 if l <= 0.5: m2 = l * (1.0+s)
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74 else: m2 = l+s-(l*s)
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75 m1 = 2.0*l - m2
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76 return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD))
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77
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78 def _v(m1, m2, hue):
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79 hue = hue % 1.0
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80 if hue < ONE_SIXTH: return m1 + (m2-m1)*hue*6.0
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81 if hue < 0.5: return m2
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82 if hue < TWO_THIRD: return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0
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83 return m1
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84
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85
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86 # HSV: Hue, Saturation, Value(?)
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87 # H: position in the spectrum
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88 # S: ???
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89 # V: ???
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90
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91 def rgb_to_hsv(r, g, b):
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92 maxc = max(r, g, b)
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93 minc = min(r, g, b)
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94 v = maxc
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95 if minc == maxc: return 0.0, 0.0, v
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96 s = (maxc-minc) / maxc
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97 rc = (maxc-r) / (maxc-minc)
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98 gc = (maxc-g) / (maxc-minc)
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99 bc = (maxc-b) / (maxc-minc)
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100 if r == maxc: h = bc-gc
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101 elif g == maxc: h = 2.0+rc-bc
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102 else: h = 4.0+gc-rc
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103 h = (h/6.0) % 1.0
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104 return h, s, v
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105
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106 def hsv_to_rgb(h, s, v):
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107 if s == 0.0: return v, v, v
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108 i = int(h*6.0) # XXX assume int() truncates!
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109 f = (h*6.0) - i
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110 p = v*(1.0 - s)
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111 q = v*(1.0 - s*f)
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112 t = v*(1.0 - s*(1.0-f))
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113 if i%6 == 0: return v, t, p
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114 if i == 1: return q, v, p
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115 if i == 2: return p, v, t
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116 if i == 3: return p, q, v
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117 if i == 4: return t, p, v
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118 if i == 5: return v, p, q
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119 # Cannot get here