function draw() {
    img.loadPixels();
    for (var y = 0; y < img.height; y++) {
        for (var x = 0; x < img.height; x++) {
            var off = (y * img.width + x) * 4;
            var c = color(img.pixels[off], img.pixels[off + 1],
                    img.pixels[off + 2], img.pixels[off + 3]);
            stroke(c);
            point(x, y);
        }
    }
};