ColorSpaceConvertions.js

/**
 * Converts an RGB color value to HSL. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes r, g, and b are contained in the set [0, 255] and
 * returns h, s, and l in the set [0, 1].
 *
 * @param   Number  r       The red color value
 * @param   Number  g       The green color value
 * @param   Number  b       The blue color value
 * @return  Array           The HSL representation
 */
export function rgb2hsl (r, g, b) {

    var rr, gg, bb,
    r = arguments[0] / 255,
    g = arguments[1] / 255,
    b = arguments[2] / 255,
    h, s,
    v = Math.max(r, g, b),
    diff = v - Math.min(r, g, b),
    diffc = function(c){
        return (v - c) / 6 / diff + 1 / 2;
    };

    if (diff == 0) {
        h = s = 0;
    } else {
        s = diff / v;
        rr = diffc(r);
        gg = diffc(g);
        bb = diffc(b);

        if (r === v) {
            h = bb - gg;
        }else if (g === v) {
            h = (1 / 3) + rr - bb;
        }else if (b === v) {
            h = (2 / 3) + gg - rr;
        }
        if (h < 0) {
            h += 1;
        }else if (h > 1) {
            h -= 1;
        }
    }
    return [h, s, v ]
}

/**
 * Converts an HSL color value to RGB. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes h, s, and l are contained in the set [0, 1] and
 * returns r, g, and b in the set [0, 255].
 *
 * @param   Number  h       The hue
 * @param   Number  s       The saturation
 * @param   Number  l       The lightness
 * @return  Array           The RGB representation
 */
export function hsl2rgb (h,s,v) {
    var r,g,b,i,f,p,q,t,hue;
    if (h.h !=null){
        v=h.b;
        s=h.s;
        h=h.h;
    }
    h%=360;
    if (h<1) h*=360;
    s=s>1?1:s<0?0:s;
    v=v>1?1:v<0?0:v;
    hue=h
    if (s==0) r=g=b=v;
    else {
        h/=60;
        f=h-(i=Math.floor(h));
        p=v*(1-s);
        q=v*(1-s*f);
        t=v*(1-s*(1-f));
        switch (i) {
            case 0:r=v; g=t; b=p; break;
            case 1:r=q; g=v; b=p; break;
            case 2:r=p; g=v; b=t; break;
            case 3:r=p; g=q; b=v; break;
            case 4:r=t; g=p; b=v; break;
            case 5:r=v; g=p; b=q; break;
        }
    }
    return [ Math.floor(r * 255), Math.floor(g * 255), Math.floor(b * 255)]
}

/**
 * Converts HEX color value to Array of integer representing the Red Green Blue channels.
 *
 * @param   Number  hex     The hex value FFFFFF
 * @return  Array of 3 Number  The RGB value [ [0, 255], [0, 255], [0, 255] ].
 */
export function hex2rgb (hex) {
    return [ (hex >> 16) & 255, (hex >> 8) & 255, hex & 255 ];
}

/**
 * Converts RGB color value to array of hex representing the Red Green Blue channels.
 *
 * @param   Number  r           red in set    [0,1]
 * @param   Number  g           green in set  [0,1]
 * @param   Number  b           blue in set   [0,1]
 * @return  Array of 3 Number   The RGB value [ [0, 255], [0, 255], [0, 255] ].
 */
export function rgb2hex ( r, g, b) {
    var hex = (r*65536+g*256+b).toString(16,6);
    while ( hex.length < 6 ) {
        hex = '0'+hex;
    }
    return hex;
}