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61 lines
1.4 KiB
61 lines
1.4 KiB
// 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 = h % 360;
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if (h < 0)
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h += 360;
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h = ~~h / 360;
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if (s < 0)
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s = 0;
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else if (s > 100)
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s = 100;
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s = ~~s / 100;
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if (l < 0)
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l = 0;
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else if (l > 100)
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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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