mirror of https://github.com/zulip/zulip.git
41 lines
1004 B
JavaScript
41 lines
1004 B
JavaScript
var colorspace = (function () {
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var exports = {};
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// 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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// http://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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} else {
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return Math.pow((v + 0.055) / 1.055, 2.4);
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}
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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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// http://en.wikipedia.org/wiki/Lab_color_space#Forward_transformation
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exports.luminance_to_lightness = function (luminance) {
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var 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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return exports;
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}());
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