Ghostrider
Administrator
Posts: 45 |
C64 color comparison
<Post edited by Ghostrider on 20/11-2024 15:37>
So, I'm playing around with something that utilizes color differences, and I wanted my code to be as good as I could make it. That led me into a little research, resulting in the below table (and documentation) in my code. I have no idea whether others have done anything like this, I just thought I'd share it in case it could be useful for someone. (Tho I guess there could be someone who doesn't like the Pepto palette). The color-differences range from 0 to 100, as can be seen from the difference between black and white.
/* COLOR-DIFFERENCE TABLE, measuring how alike 2 colors look to the human eye.
*
* Created by translating the correct C64 RGB-palette (as thoroughly researched
* by Philip 'Pepto' Timmermann, and published in the "Commodore VIC-II Color
* Analysis"):
*
* Black White Red Cyan Purple Green Blue
* 00 00 00 ff ff ff 68 37 2b 70 a4 b2 6f 3d 86 58 8d 43 35 28 79
*
* Yellow Orange Brown Lt Red Dark Grey Med Grey Lt green
* b8 c7 6f 6f 4f 25 43 39 00 9a 67 59 44 44 44 6c 6c 6c 9a d2 84
*
* Lt Blue Lt Grey
* 6c 5e b5 95 95 95
*
*
* into the intended perceptually uniform CIE L*a*b* (CIELAB) color space via
* Photoshop CS5:
*
* Black White Red Cyan Purple Green Blue
* 0 0 0 100 0 0 29 21 18 64 -15 -13 35 32 -32 54 -29 33 22 25 -45
*
* Yellow Orange Brown Lt Red Dark Grey Med Grey Lt green
* 78 -15 42 36 10 30 24 0 33 49 20 17 29 0 0 46 0 0 79 -29 33
*
* Lt Blue Lt Grey
* 44 22 -45 62 0 0
*
* and finally, using the above CIE L*a*b* values, computing the
* color-differences between any two C64 colors. This was done using a Matlab
* implementation of the CIEDE2000 color-difference formula, published by
* Gaurav Sharma at the University of Rochester. As of 2016, this should be the
* best visual-color-difference algorithm available.
*/
float colordiff[16][16] = {
{0.00000, 100.00000, 27.29927, 53.26580, 33.36977, 46.54540, 27.91278,
71.32101, 30.91014, 24.36201, 40.40526, 18.97503, 32.86756, 72.80412,
39.20668, 48.53537},
{100.00000, 0.00000, 61.97257, 29.34183, 56.93753, 40.24329, 71.85536,
26.50693, 54.14554, 67.73280, 42.05900, 58.78266, 40.33892, 26.72007,
48.58504, 26.02320},
{27.29927, 61.97257, 0.00000, 53.66487, 28.72115, 44.76018, 33.08048,
56.92023, 14.00707, 21.06269, 17.36067, 19.62648, 24.37162, 61.72667,
35.29397, 37.10740},
{53.26580, 29.34183, 53.66487, 0.00000, 38.60884, 30.82463, 43.73660,
34.43323, 43.05106, 48.64282, 43.62700, 37.61613, 23.58306, 31.63124,
27.79863, 16.38323},
{33.36977, 56.93753, 28.72115, 38.60884, 0.00000, 63.67504, 13.95492,
69.94213, 40.00703, 47.52039, 30.66366, 24.06466, 25.52344, 73.27806,
13.99189, 35.70972},
{46.54540, 40.24329, 44.76018, 30.82463, 63.67504, 0.00000, 55.77398,
21.74555, 31.80033, 31.80176, 38.51345, 32.30988, 24.56106, 20.17950,
49.67790, 24.32458},
{27.91278, 71.85536, 33.08048, 43.73660, 13.95492, 55.77398, 0.00000,
80.90839, 43.71174, 48.31631, 39.23529, 24.73801, 31.07341, 74.86371,
17.74707, 43.54902},
{71.32101, 26.50693, 56.92023, 34.43323, 69.94213, 21.74555, 80.90839,
0.00000, 42.97277, 54.79072, 39.45047, 52.55362, 35.47933, 9.66140,
64.56892, 25.73341},
{30.91014, 54.14554, 14.00707, 43.05106, 40.00703, 31.80033, 43.71174,
42.97277, 0.00000, 12.50487, 17.45413, 19.77869, 20.96770, 47.52027,
42.70317, 32.11929},
{24.36201, 67.73280, 21.06269, 48.64282, 47.52039, 31.80176, 48.31631,
54.79072, 12.50487, 0.00000, 29.37105, 19.29903, 26.19519, 57.58782,
50.39976, 39.71692},
{40.40526, 42.05900, 17.36067, 43.62700, 30.66366, 38.51345, 39.23529,
39.45047, 17.45413, 29.37105, 0.00000, 25.82295, 19.35305, 45.64642,
32.88847, 22.69667},
{18.97503, 58.78266, 19.62648, 37.61613, 24.06466, 32.30988, 24.73801,
52.55362, 19.77869, 19.29903, 25.82295, 0.00000, 14.44913, 53.39135,
26.98485, 31.49222},
{32.86756, 40.33892, 24.37162, 23.58306, 25.52344, 24.56106, 31.07341,
35.47933, 20.96770, 26.19519, 19.35305, 14.44913, 0.00000, 36.41365,
23.94736, 15.38462},
{72.80412, 26.72007, 61.72667, 31.63124, 73.27806, 20.17950, 74.86371,
9.66140, 47.52027, 57.58782, 45.64642, 53.39135, 36.41365, 0.00000,
57.25129, 26.64841},
{39.20668, 48.58504, 35.29397, 27.79863, 13.99189, 49.67790, 17.74707,
64.56892, 42.70317, 50.39976, 32.88847, 26.98485, 23.94736, 57.25129,
0.00000, 29.63502},
{48.53537, 26.02320, 37.10740, 16.38323, 35.70972, 24.32458, 43.54902,
25.73341, 32.11929, 39.71692, 22.69667, 31.49222, 15.38462, 26.64841,
29.63502, 0.00000}
};
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