Get Colors From Image

gistfile1.js

// Create a new image
var image = new Image();
var imageData = false;
image.crossOrigin = '';
image.src = 'http://p.gkoberger.net/firefox/firefox.png';

// When it loads, we’re going to put it into a canvas element
image.onload = function () {
    var cnvs = document.createElement('canvas');
    cnvs.width = image.width;
    cnvs.height = image.height;

    document.getElementsByTagName('body')[0].appendChild(cnvs);

    // This gives the drawing methods we need.
    var ctx = cnvs.getContext('2d');
    ctx.drawImage(image, 0, 0);

    // Only some browsers support getImageData.
    try {
        imageData = ctx.getImageData(0, 0, cnvs.width, cnvs.height);
    } catch (e) {
        alert("Your browser doesn’t support");
        return;
    }
};

// Returns RGBA
function getColor(x, y) {
    if (!imageData) return;

    // Weird math to get the index; just trust me on this one
    var index = (y * imageData.width + x) * 4,
        red = imageData.data[index],
        green = imageData.data[index + 1],
        blue = imageData.data[index + 2],
        alpha = imageData.data[index + 3];

    // I’m returning RGBA, since it’s something we can use when writing HTML
    return "rgba(" + red + "," + green + "," + blue + "," + alpha + ");";
}