shader.data.imgSize.value = [512,512];
          shader.data.center.value = [200.0,200.0];
          shader.data.offset.value = [0,0];
          } 
         
    filter = new ShaderFilter(shader);
  
    //add the filter to the image
    stack.filters = [filter];
    stage.addEventListener(Event.ENTER_FRAME, loop);
    }
   ]]>
   </mx:Script>