compiled JS from: https://gist.github.com/3818959

gistfile1.js

var MapController = (function () {
    function MapController(canvas, imagePath) {
        this.canvas = canvas;
        this.imagePath = imagePath;
        this._canvas = canvas;
        this._canvas.width = 960;
        this._canvas.height = 640;
        this._ctx = this._canvas.getContext('2d');
        this._that = this;
        this._image = new Image();
        this._image.onload = (function (parent) {
            return function () {
                parent.imageReady();
            }
        })(this);
        this._image.src = imagePath;
    }
    MapController.prototype.imageReady = function () {
        console.log("here");
        console.log("image w:" + this._image.width + " h:" + this._image.height);
        this._ctx.drawImage(this._image, 0, 0, 960, 640);
    };
    MapController.prototype.sample = function () {
        this._ctx.strokeStyle = "#ff0000";
        this._ctx.beginPath();
        this._ctx.moveTo(25, 25);
        this._ctx.lineTo(105, 25);
        this._ctx.lineTo(25, 105);
        this._ctx.fill();
    };
    return MapController;
})();