Get rgb values of a color, convert them to hsl values and adjust the lightness of the color

example.js

var color = 'rgb(10, 24, 180)';

var rgb   = getRgbValues(color);
var red   = rgb[0];
var green = rgb[1];
var blue  = rgb[2];

var hsl        = rgb2Hsl(red, green ,blue);
var hue        = hsl[0];
var saturation = hsl[1];
var lightness  = hsl[2];

var newColor   = 'hsl(' + hue + ', ' + saturation + '%, 40%)';        

getRgbValues.js

// Color lookup buffer
var lookupBuffer    = doc.createElement('canvas');
lookupBuffer.width  = 1;
lookupBuffer.height = 1;
var lookupCtx       = lookupBuffer.getContext('2d');


var getRgbValues = function(color) {    
    lookupCtx.beginPath();
    lookupCtx.rect(0, 0, 1, 1);
    lookupCtx.fillStyle = color;
    lookupCtx.fill();
    var rgbData = lookupCtx.getImageData(0, 0, 1, 1).data;
    lookupCtx.clearRect(0, 0, 1, 1);
    return new Array(rgbData[0], rgbData[1], rgbData[2]);
};

rgb2Hsl.js

var rgb2Hsl = function(red, green, blue) {
    red   /= 255;
    green /= 255;
    blue  /= 255;

    var max = Math.max(red, green, blue);
    var min = Math.min(red, green, blue);
    var hue;
    var saturation;
    var lightness = (max + min) / 2;

    if (max == min) {
        hue = saturation = 0; // achromatic
    } else {
        var delta = max - min;
        saturation = lightness > 0.5 ? delta / (2 - max - min) : delta / (max + min);
        switch (max) {
            case red:
                hue = (green - blue) / delta + (green < blue ? 6 : 0);
                break;
            case green:
                hue = (blue - red) / delta + 2;
                break;
            case blue:
                hue = (red - green) / delta + 4;
                break;
        }
        hue /= 6;
    }
    return [(hue * 360), (saturation * 100), (lightness * 100)];
}