77 lines
1.6 KiB
JavaScript
77 lines
1.6 KiB
JavaScript
/**
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* OSA-UCS
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*
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* @module color-space/osa-ucs
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*/
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import xyz from './xyz.js';
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var osaucs = {
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name: 'osaucs',
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alias: ['OSA-UCS'],
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channel: ['L', 'j', 'g'],
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min: [-10, -6, -10],
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max: [8, 12, 6]
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};
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/**
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* There’s no analytical solution to this
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*/
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osaucs.xyz = function (arg) {
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var x, y, z;
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throw 'Unimplemented';
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//http://www.researchgate.net/publication/259253763_Comparison_of_the_performance_of_inverse_transformation_methods_from_OSA-UCS_to_CIEXYZ
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return [x, y, z];
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};
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/**
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* Transform to xyz osaucs
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*
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* @param {Array<number>} arg Input xyz array
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*
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* @return {Array<number>} Ljg array
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*/
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xyz.osaucs = function (arg) {
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var X = arg[0], Y = arg[1], Z = arg[2];
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var x = X / (X + Y + Z);
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var y = Y / (X + Y + Z);
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//FIXME: there might be a typo, wiki states 1.8103 as a constant value
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var K = 4.4934 * x * x + 4.3034 * y * y - 4.276 * x * y - 1.3744 * x - 2.56439 * y + 1.8103;
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var Y0 = K * Y;
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var L_ = 5.9 * (Math.pow(Y0, 1 / 3) - 2 / 3 + 0.042 * Math.pow(Math.max(Y0, 30) - 30, 1 / 3));
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var L = (L_ - 14.3993) / Math.sqrt(2);
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var C = L_ / (5.9 * (Math.pow(Y0, 1 / 3) - 2 / 3));
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var R = 0.7790 * X + 0.4194 * Y - 0.1648 * Z;
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var G = -0.4493 * X + 1.3265 * Y + 0.0927 * Z;
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var B = -0.1149 * X + 0.3394 * Y + 0.7170 * Z;
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R = Math.pow(R, 1 / 3) || 0;
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G = Math.pow(G, 1 / 3) || 0;
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B = Math.pow(B, 1 / 3) || 0;
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var a = -13.7 * R + 17.7 * G - 4 * B;
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var b = 1.7 * R + 8 * G - 9.7 * B;
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var g = C * a;
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var j = C * b;
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//polar form
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// var p = Math.sqrt(j*j + g*g);
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// var phi = Math.atan2(j, g);
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return [L, j, g];
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};
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export default (osaucs);
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