Test of various hsl2rgb conversions

hst2rgb-test.js

var assert = require('assert');

var tests = [
    {hsl: [0, 0, 0], rgb: [0, 0, 0]},           // black
    {hsl: [0, 0, 1], rgb: [255, 255, 255]},     // white
    {hsl: [0, 1, 0.5], rgb: [255, 0, 0]},       // red
    {hsl: [120, 1, 0.5], rgb: [0, 255, 0]},     // green
    {hsl: [240, 1, 0.5], rgb: [0, 0, 255]},     // blue

    // http://www.december.com/html/spec/colorcodes.html
    {hsl: [205, 0.55, 0.75], rgb: [155, 196, 226]},     // cerulean blue
    {hsl: [131, 0.91, 0.86], rgb: [189, 252, 201]},     // mint green
    {hsl: [9, 0.59, 0.34], rgb: [138, 51, 36]},         // burnt umber

    // Brokers
    // Calculations from http://serennu.com/colour/hsltorgb.php
    {hsl: [350, 0.9, 0.1], rgb: [48, 3, 10]},
    {hsl: [350, 0.9, 0.5], rgb: [242, 13, 51]},
    {hsl: [350, 0.9, 0.8], rgb: [250, 158, 173]},
];

var converters = [ 
    // From node-tint
    function (h, s, l) {
        if (!s) return [l * 255, l * 255, l * 255];

        var v = l <= 0.5 ? l*(1+s) : l+s-l*s;
        if (!v) return [0, 0, 0];

        var min = 2*l-v;
        var sv = (v-min)/l
        h = (h % 360) / 60;
        var sextant = h | 0;
        var fract = h-sextant;
        v *= 255;
        min *= 255;
        switch (sextant) {
            case 0: return [Math.round(v), Math.round(min+v*sv*fract), Math.round(min)];
            case 1: return [Math.round(v-v*sv*fract), Math.round(v), Math.round(min)];
            case 2: return [Math.round(min), Math.round(v), Math.round(min+v*sv*fract)];
            case 3: return [Math.round(min), Math.round(v-v*sv*fract), Math.round(v)];
            case 4: return [Math.round(min+v*sv*fract), Math.round(min), Math.round(v)];
            case 5: return [Math.round(v), Math.round(min), Math.round(v-v*sv*fract)];
        }
    },
    // From farbtastic
    function(h, s, l) {
        // normalize input.
        h = h / 360;

        var m1, m2, r, g, b;

        var hueToRGB = function (m1, m2, h) {
            h = (h + 1) % 1;
            if (h * 6 < 1) return m1 + (m2 - m1) * h * 6;
            if (h * 2 < 1) return m2;
            if (h * 3 < 2) return m1 + (m2 - m1) * (0.66666 - h) * 6;
            return m1;
        };

        m2 = (l <= 0.5) ? l * (s + 1) : l + s - l * s;
        m1 = l * 2 - m2;
        return [
          hueToRGB(m1, m2, h + 0.33333) * 255,
          hueToRGB(m1, m2, h) * 255,
          hueToRGB(m1, m2, h - 0.33333) * 255
        ];
    },
    // @see http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
    function (h, s, l) {
        // normalize input.
        h = h / 360;

        var r, g, b;

        if (s == 0) {
            r = g = b = l; // achromatic
        } else {
            function hue2rgb(p, q, t){
                if(t < 0) t += 1;
                if(t > 1) t -= 1;
                if(t < 1/6) return p + (q - p) * 6 * t;
                if(t < 1/2) return q;
                if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
                return p;
            }

            var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
            var p = 2 * l - q;
            r = hue2rgb(p, q, h + 1/3);
            g = hue2rgb(p, q, h);
            b = hue2rgb(p, q, h - 1/3);
        }
        return [r * 255, g * 255, b * 255];
    }
];

var run = 0;
var fail = 0;
converters.forEach(function(hsl2rgb, idx) {
    console.warn("Method " + (idx + 1));
    tests.forEach(function(test) {
        run++;
        var rgb = hsl2rgb(test.hsl[0], test.hsl[1],test.hsl[2]);
        rgb[0] = Math.round(rgb[0]);
        rgb[1] = Math.round(rgb[1]);
        rgb[2] = Math.round(rgb[2]);

        try {
            assert.deepEqual(test.rgb, rgb);
        }
        catch(e) {
            fail++
            console.warn(">> " + e.toString());
        }
    });
});

console.log(">> Passed " + (run - fail) + " of " + run);