Source: utils/Canvas.js

(function() {
 /**
 * Canvas utility.
 * @static
 * @constructor
 */
 tracking.Canvas = {};
 /**
 * Loads an image source into the canvas.
 * @param {HTMLCanvasElement} canvas The canvas dom element.
 * @param {string} src The image source.
 * @param {number} x The canvas horizontal coordinate to load the image.
 * @param {number} y The canvas vertical coordinate to load the image.
 * @param {number} width The image width.
 * @param {number} height The image height.
 * @param {function} opt_callback Callback that fires when the image is loaded
 * into the canvas.
 * @static
 */
 tracking.Canvas.loadImage = function(canvas, src, x, y, width, height, opt_callback) {
 var instance = this;
 var img = new window.Image();
 img.onload = function() {
 var context = canvas.getContext('2d');
 canvas.width = width;
 canvas.height = height;
 context.drawImage(img, x, y, width, height);
 if (opt_callback) {
 opt_callback.call(instance);
 }
 img = null;
 };
 img.src = src;
 };
}());