var ImagePreloader = Class.create();
ImagePreloader.prototype = {
 initialize: function(imageSrc, callback) {
 this.imageSrc=imageSrc;
 this.callback=callback;
 this.image = new Image();
 this.image.onload = this.__onComplete.bind(this);
 this.image.src=imageSrc;
 },

 __onComplete: function() {
 this.callback(this);
 }
};