MovieClip.prototype.loadImage = function(img) {
   var c = this.createEmptyMovieClip("container", 0);
   c.loadMovie(img);
   this.onEnterFrame = function() {
      var percent = Math.round((c.getBytesLoaded()/c.getBytesTotal())*100);
      if (percent>99) {
         delete this.onEnterFrame;
         this.onContentLoaded();
      }
   };
};
//------------------------------------------------------------------


_root.createEmptyMovieClip("a", 0);
a.loadImage("1.jpg");
a.onContentLoaded = function() {
   trace(_height);
};