mirror of https://github.com/cheeaun/phanpy
53 lines
2.0 KiB
JavaScript
53 lines
2.0 KiB
JavaScript
// https://gist.github.com/earthbound19/e7fe15fdf8ca3ef814750a61bc75b5ce
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function clamp(value, min, max) {
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return Math.max(Math.min(value, max), min);
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}
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const gammaToLinear = (c) =>
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c >= 0.04045 ? Math.pow((c + 0.055) / 1.055, 2.4) : c / 12.92;
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const linearToGamma = (c) =>
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c >= 0.0031308 ? 1.055 * Math.pow(c, 1 / 2.4) - 0.055 : 12.92 * c;
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export function rgb2oklab([r, g, b]) {
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r = gammaToLinear(r / 255);
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g = gammaToLinear(g / 255);
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b = gammaToLinear(b / 255);
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var l = 0.4122214708 * r + 0.5363325363 * g + 0.0514459929 * b;
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var m = 0.2119034982 * r + 0.6806995451 * g + 0.1073969566 * b;
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var s = 0.0883024619 * r + 0.2817188376 * g + 0.6299787005 * b;
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l = Math.cbrt(l);
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m = Math.cbrt(m);
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s = Math.cbrt(s);
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return [
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l * +0.2104542553 + m * +0.793617785 + s * -0.0040720468,
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l * +1.9779984951 + m * -2.428592205 + s * +0.4505937099,
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l * +0.0259040371 + m * +0.7827717662 + s * -0.808675766,
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];
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}
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export function oklab2rgb([L, a, b]) {
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var l = L + a * +0.3963377774 + b * +0.2158037573;
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var m = L + a * -0.1055613458 + b * -0.0638541728;
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var s = L + a * -0.0894841775 + b * -1.291485548;
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// The ** operator here cubes; same as l_*l_*l_ in the C++ example:
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l = l ** 3;
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m = m ** 3;
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s = s ** 3;
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var r = l * +4.0767416621 + m * -3.3077115913 + s * +0.2309699292;
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var g = l * -1.2684380046 + m * +2.6097574011 + s * -0.3413193965;
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var b = l * -0.0041960863 + m * -0.7034186147 + s * +1.707614701;
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// Convert linear RGB values returned from oklab math to sRGB for our use before returning them:
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r = 255 * linearToGamma(r);
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g = 255 * linearToGamma(g);
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b = 255 * linearToGamma(b);
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// OPTION: clamp r g and b values to the range 0-255; but if you use the values immediately to draw, JavaScript clamps them on use:
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r = clamp(r, 0, 255);
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g = clamp(g, 0, 255);
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b = clamp(b, 0, 255);
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// OPTION: round the values. May not be necessary if you use them immediately for rendering in JavaScript, as JavaScript (also) discards decimals on render:
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r = Math.round(r);
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g = Math.round(g);
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b = Math.round(b);
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return [r, g, b];
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}
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