mirror of https://github.com/zulip/zulip.git
53 lines
1.6 KiB
JavaScript
53 lines
1.6 KiB
JavaScript
// Convert an sRGB value in [0, 255] to a linear intensity
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// value in [0, 1].
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//
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// https://en.wikipedia.org/wiki/SRGB#The_reverse_transformation
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exports.sRGB_to_linear = function (v) {
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v = v / 255.0;
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if (v <= 0.04045) {
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return v / 12.92;
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}
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return Math.pow((v + 0.055) / 1.055, 2.4);
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};
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// Compute luminance (CIE Y stimulus) from linear intensity
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// of sRGB / Rec. 709 primaries.
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exports.rgb_luminance = function (channel) {
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return 0.2126 * channel[0] + 0.7152 * channel[1] + 0.0722 * channel[2];
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};
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// Convert luminance (photometric, CIE Y)
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// to lightness (perceptual, CIE L*)
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//
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// https://en.wikipedia.org/wiki/Lab_color_space#Forward_transformation
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exports.luminance_to_lightness = function (luminance) {
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let v;
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if (luminance <= 216 / 24389) {
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v = 841 / 108 * luminance + 4 / 29;
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} else {
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v = Math.pow(luminance, 1 / 3);
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}
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return 116 * v - 16;
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};
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exports.getDecimalColor = function (hexcolor) {
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return {r: parseInt(hexcolor.substr(1, 2), 16),
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g: parseInt(hexcolor.substr(3, 2), 16),
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b: parseInt(hexcolor.substr(5, 2), 16)};
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};
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exports.getLighterColor = function (rgb, lightness) {
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return {r: Math.round(lightness * 255 + (1 - lightness) * rgb.r),
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g: Math.round(lightness * 255 + (1 - lightness) * rgb.g),
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b: Math.round(lightness * 255 + (1 - lightness) * rgb.b)};
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};
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exports.getHexColor = function (rgb) {
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return "#" + parseInt(rgb.r, 10).toString(16) +
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parseInt(rgb.g, 10).toString(16) +
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parseInt(rgb.b, 10).toString(16);
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};
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window.colorspace = exports;
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