RGBtoRGBA

gistfile1.js

function RGBtoRGBA(r, g, b){
    (g==void 0) && (typeof r == 'string') &&
        (r = r.replace(/^\s*#|\s*$/g, ''),
         (r.length == 3) && (r = r.replace(/(.)/g, '$1$1')),
         g = parseInt(r.substr(2, 2), 16),
         b = parseInt(r.substr(4, 2), 16),
         r = parseInt(r.substr(0, 2), 16));

    var min, a = ( 255 - (min = Math.min(r, g, b)) ) / 255;

    return {
        r    : r = 0|( r - min ) / a,
        g    : g = 0|( g - min ) / a,
        b    : b = 0|( b - min ) / a,
        a    : a = (0|1000*a)/1000,
        rgba : 'rgba(' + r + ', ' + g + ', ' + b + ', ' + a + ')'
    };
}