55 lines
1.4 KiB
JavaScript
55 lines
1.4 KiB
JavaScript
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// HSL to RGB converter. Both methods adapted from:
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// http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
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function hslToRgb(h, s, l) {
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var r, g, b;
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// normalize hue orientation b/w 0 and 360 degrees
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h %= 360;
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if (h < 0) { h += 360; }
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h = ~~h / 360;
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if (s < 0) { s = 0; } else if (s > 100) { s = 100; }
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s = ~~s / 100;
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if (l < 0) { l = 0; } else if (l > 100) { l = 100; }
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l = ~~l / 100;
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if (s === 0) {
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r = g = b = l; // achromatic
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} else {
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var q = l < 0.5
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? l * (1 + s)
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: l + s - l * s;
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var p = 2 * l - q;
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r = hueToRgb(p, q, h + 1 / 3);
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g = hueToRgb(p, q, h);
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b = hueToRgb(p, q, h - 1 / 3);
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}
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return [~~(r * 255), ~~(g * 255), ~~(b * 255)];
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}
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function hueToRgb(p, q, t) {
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if (t < 0) { t += 1; }
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if (t > 1) { t -= 1; }
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if (t < 1 / 6) { return p + (q - p) * 6 * t; }
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if (t < 1 / 2) { return q; }
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if (t < 2 / 3) { return p + (q - p) * (2 / 3 - t) * 6; }
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return p;
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}
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function shortenHsl(hue, saturation, lightness) {
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var asRgb = hslToRgb(hue, saturation, lightness);
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var redAsHex = asRgb[0].toString(16);
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var greenAsHex = asRgb[1].toString(16);
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var blueAsHex = asRgb[2].toString(16);
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return '#'
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+ ((redAsHex.length == 1 ? '0' : '') + redAsHex)
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+ ((greenAsHex.length == 1 ? '0' : '') + greenAsHex)
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+ ((blueAsHex.length == 1 ? '0' : '') + blueAsHex);
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}
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module.exports = shortenHsl;
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