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72 lines
1.9 KiB
JavaScript
72 lines
1.9 KiB
JavaScript
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// http://stackoverflow.com/questions/2353211/hsl-to-rgb-color-conversion
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/**
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* Converts an HSL color value to RGB. Conversion formula
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* adapted from http://en.wikipedia.org/wiki/HSL_color_space.
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* Assumes h, s, and l are contained in the set [0, 1] and
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* returns r, g, and b in the set [0, 255].
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*
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* @param Number h The hue
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* @param Number s The saturation
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* @param Number l The lightness
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* @return Array The RGB representation
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*/
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function hslToRgb(h, s, l){
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var r, g, b;
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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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function hue2rgb(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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var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
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var p = 2 * l - q;
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r = hue2rgb(p, q, h + 1/3);
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g = hue2rgb(p, q, h);
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b = hue2rgb(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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/**
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* Converts an RGB color value to HSL. Conversion formula
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* adapted from http://en.wikipedia.org/wiki/HSL_color_space.
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* Assumes r, g, and b are contained in the set [0, 255] and
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* returns h, s, and l in the set [0, 1].
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*
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* @param Number r The red color value
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* @param Number g The green color value
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* @param Number b The blue color value
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* @return Array The HSL representation
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*/
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function rgbToHsl(r, g, b){
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r /= 255, g /= 255, b /= 255;
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var max = Math.max(r, g, b), min = Math.min(r, g, b);
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var h, s, l = (max + min) / 2;
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if(max == min){
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h = s = 0; // achromatic
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}else{
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var d = max - min;
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s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
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switch(max){
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case r: h = (g - b) / d + (g < b ? 6 : 0); break;
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case g: h = (b - r) / d + 2; break;
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case b: h = (r - g) / d + 4; break;
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}
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h /= 6;
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}
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return [h, s, l];
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}
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