HSL.js

module.exports = function HSL(color) {
    color.use(require('./HSV'));

    color.installColorSpace('HSL', ['hue', 'saturation', 'lightness', 'alpha'], {
        hsv: function () {
            // Algorithm adapted from http://wiki.secondlife.com/wiki/Color_conversion_scripts
            var l = this._lightness * 2,
                s = this._saturation * ((l <= 1) ? l : 2 - l),
                saturation;

            // Avoid division by zero when l + s is very small (approaching black):
            if (l + s < 1e-9) {
                saturation = 0;
            } else {
                saturation = (2 * s) / (l + s);
            }

            return new color.HSV(this._hue, saturation, (l + s) / 2, this._alpha);
        },

        rgb: function () {
            return this.hsv().rgb();
        },

        fromRgb: function () { // Becomes one.color.RGB.prototype.hsv
            return this.hsv().hsl();
        }
    });
};