Change a colors luminosity

changeColorLuminosity

var changeColorLuminosity = function (hexcolor, luminosity) {
    var hex = hexcolor.replace(/[^0-9a-f]/gi, '');

    // convert to decimal and change luminosity
    var rgb = "#", c, i;
    for (i = 0; i < 3; i++) {
        c = parseInt(hex.substr(i * 2, 2), 16);
        c = Math.round(Math.min(Math.max(0, c + (c * luminosity)), 255)).toString(16);
        rgb += ("00" + c).substr(c.length);
    }

    return rgb;
};