Fred Drake | 8720917 | 1999-02-25 14:24:22 +0000 | [diff] [blame] | 1 | """Conversion functions between RGB and other color systems. |
| 2 | |
| 3 | This modules provides two functions for each color system ABC: |
| 4 | |
| 5 | rgb_to_abc(r, g, b) --> a, b, c |
Fred Drake | bff3ae1 | 1999-02-25 14:26:02 +0000 | [diff] [blame] | 6 | abc_to_rgb(a, b, c) --> r, g, b |
Fred Drake | 8720917 | 1999-02-25 14:24:22 +0000 | [diff] [blame] | 7 | |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 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. |
Fred Drake | 8720917 | 1999-02-25 14:24:22 +0000 | [diff] [blame] | 11 | |
| 12 | Supported color systems: |
| 13 | RGB: Red, Green, Blue components |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 14 | YIQ: Luminance, Chrominance (used by composite video signals) |
Fred Drake | b217687 | 2000-02-14 21:30:52 +0000 | [diff] [blame] | 15 | HLS: Hue, Luminance, Saturation |
| 16 | HSV: Hue, Saturation, Value |
Fred Drake | 8720917 | 1999-02-25 14:24:22 +0000 | [diff] [blame] | 17 | """ |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 18 | |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 19 | # References: |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 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 |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 23 | |
Skip Montanaro | e99d5ea | 2001-01-20 19:54:20 +0000 | [diff] [blame] | 24 | __all__ = ["rgb_to_yiq","yiq_to_rgb","rgb_to_hls","hls_to_rgb", |
| 25 | "rgb_to_hsv","hsv_to_rgb"] |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 26 | |
| 27 | # Some floating point constants |
| 28 | |
| 29 | ONE_THIRD = 1.0/3.0 |
| 30 | ONE_SIXTH = 1.0/6.0 |
| 31 | TWO_THIRD = 2.0/3.0 |
| 32 | |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 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 |
Serhiy Storchaka | 9b855de | 2013-08-06 11:51:23 +0300 | [diff] [blame] | 36 | # |
| 37 | # There are a great many versions of the constants used in these formulae. |
| 38 | # The ones in this library uses constants from the FCC version of NTSC. |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 39 | |
| 40 | def rgb_to_yiq(r, g, b): |
| 41 | y = 0.30*r + 0.59*g + 0.11*b |
Serhiy Storchaka | 9b855de | 2013-08-06 11:51:23 +0300 | [diff] [blame] | 42 | i = 0.74*(r-y) - 0.27*(b-y) |
| 43 | q = 0.48*(r-y) + 0.41*(b-y) |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 44 | return (y, i, q) |
| 45 | |
| 46 | def yiq_to_rgb(y, i, q): |
Serhiy Storchaka | 9b855de | 2013-08-06 11:51:23 +0300 | [diff] [blame] | 47 | # r = y + (0.27*q + 0.41*i) / (0.74*0.41 + 0.27*0.48) |
| 48 | # b = y + (0.74*q - 0.48*i) / (0.74*0.41 + 0.27*0.48) |
| 49 | # g = y - (0.30*(r-y) + 0.11*(b-y)) / 0.59 |
| 50 | |
| 51 | r = y + 0.9468822170900693*i + 0.6235565819861433*q |
| 52 | g = y - 0.27478764629897834*i - 0.6356910791873801*q |
| 53 | b = y - 1.1085450346420322*i + 1.7090069284064666*q |
| 54 | |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 55 | if r < 0.0: |
| 56 | r = 0.0 |
| 57 | if g < 0.0: |
| 58 | g = 0.0 |
| 59 | if b < 0.0: |
| 60 | b = 0.0 |
| 61 | if r > 1.0: |
| 62 | r = 1.0 |
| 63 | if g > 1.0: |
| 64 | g = 1.0 |
| 65 | if b > 1.0: |
| 66 | b = 1.0 |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 67 | return (r, g, b) |
| 68 | |
| 69 | |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 70 | # HLS: Hue, Luminance, Saturation |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 71 | # H: position in the spectrum |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 72 | # L: color lightness |
| 73 | # S: color saturation |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 74 | |
| 75 | def rgb_to_hls(r, g, b): |
| 76 | maxc = max(r, g, b) |
| 77 | minc = min(r, g, b) |
| 78 | # XXX Can optimize (maxc+minc) and (maxc-minc) |
| 79 | l = (minc+maxc)/2.0 |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 80 | if minc == maxc: |
| 81 | return 0.0, l, 0.0 |
| 82 | if l <= 0.5: |
| 83 | s = (maxc-minc) / (maxc+minc) |
| 84 | else: |
| 85 | s = (maxc-minc) / (2.0-maxc-minc) |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 86 | rc = (maxc-r) / (maxc-minc) |
| 87 | gc = (maxc-g) / (maxc-minc) |
| 88 | bc = (maxc-b) / (maxc-minc) |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 89 | if r == maxc: |
| 90 | h = bc-gc |
| 91 | elif g == maxc: |
| 92 | h = 2.0+rc-bc |
| 93 | else: |
| 94 | h = 4.0+gc-rc |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 95 | h = (h/6.0) % 1.0 |
| 96 | return h, l, s |
| 97 | |
| 98 | def hls_to_rgb(h, l, s): |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 99 | if s == 0.0: |
| 100 | return l, l, l |
| 101 | if l <= 0.5: |
| 102 | m2 = l * (1.0+s) |
| 103 | else: |
| 104 | m2 = l+s-(l*s) |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 105 | m1 = 2.0*l - m2 |
| 106 | return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD)) |
| 107 | |
| 108 | def _v(m1, m2, hue): |
| 109 | hue = hue % 1.0 |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 110 | if hue < ONE_SIXTH: |
| 111 | return m1 + (m2-m1)*hue*6.0 |
| 112 | if hue < 0.5: |
| 113 | return m2 |
| 114 | if hue < TWO_THIRD: |
| 115 | return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0 |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 116 | return m1 |
| 117 | |
| 118 | |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 119 | # HSV: Hue, Saturation, Value |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 120 | # H: position in the spectrum |
Fredrik Lundh | 0d89e35 | 2005-11-12 15:21:05 +0000 | [diff] [blame] | 121 | # S: color saturation ("purity") |
| 122 | # V: color brightness |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 123 | |
| 124 | def rgb_to_hsv(r, g, b): |
| 125 | maxc = max(r, g, b) |
| 126 | minc = min(r, g, b) |
| 127 | v = maxc |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 128 | if minc == maxc: |
| 129 | return 0.0, 0.0, v |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 130 | s = (maxc-minc) / maxc |
| 131 | rc = (maxc-r) / (maxc-minc) |
| 132 | gc = (maxc-g) / (maxc-minc) |
| 133 | bc = (maxc-b) / (maxc-minc) |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 134 | if r == maxc: |
| 135 | h = bc-gc |
| 136 | elif g == maxc: |
| 137 | h = 2.0+rc-bc |
| 138 | else: |
| 139 | h = 4.0+gc-rc |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 140 | h = (h/6.0) % 1.0 |
| 141 | return h, s, v |
| 142 | |
| 143 | def hsv_to_rgb(h, s, v): |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 144 | if s == 0.0: |
| 145 | return v, v, v |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 146 | i = int(h*6.0) # XXX assume int() truncates! |
| 147 | f = (h*6.0) - i |
| 148 | p = v*(1.0 - s) |
| 149 | q = v*(1.0 - s*f) |
| 150 | t = v*(1.0 - s*(1.0-f)) |
Thomas Wouters | 89f507f | 2006-12-13 04:49:30 +0000 | [diff] [blame] | 151 | i = i%6 |
Benjamin Peterson | c4bbc8d | 2009-01-30 03:39:35 +0000 | [diff] [blame] | 152 | if i == 0: |
| 153 | return v, t, p |
| 154 | if i == 1: |
| 155 | return q, v, p |
| 156 | if i == 2: |
| 157 | return p, v, t |
| 158 | if i == 3: |
| 159 | return p, q, v |
| 160 | if i == 4: |
| 161 | return t, p, v |
| 162 | if i == 5: |
| 163 | return v, p, q |
Guido van Rossum | 87b7473 | 1992-09-07 09:41:48 +0000 | [diff] [blame] | 164 | # Cannot get here |