code: function() {
          //TODO de-uglify opacity handling
          OpenLayers.Tile.Image.prototype.onImageLoad.apply(this, arguments);
          if (this.useIFrame === true) {
              this.imgDiv.style.opacity = 1;
              this.frame.style.opacity = this.layer.opacity;
          }
      }
docs: Method: onImageLoad
  Handler for the image onload event