as3自带 bitmapdata 像素级碰撞检测

package
{
    import flash.display.Bitmap;
    import flash.display.BitmapData;
    import flash.display.Shape;
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    import flash.events.MouseEvent;
    import flash.filters.GlowFilter;
    import flash.geom.Matrix;
    import flash.geom.Point;
    
    [SWF(width="1000",height="600")]
    public class Bitbdhitest extends Sprite
    {
        private var bd1:Bitmap;
        private var bd2:Bitmap;
        
        public function Bitbdhitest()
        {
            super();
            stage.scaleMode=StageScaleMode.NO_SCALE;
            stage.align=StageAlign.TOP_LEFT;
            init();
        }
        
        private function init():void
        {
            var bdp1:BitmapData=new BitmapData(100,100,true,0);
            bdp1.draw(getstar(50),new Matrix(1,0,0,1,50,50));
            
            bd1=new Bitmap(bdp1);
            bd1.x=200;
            bd1.y=200;
            this.addChild(bd1);
        
            var bdp2:BitmapData=new BitmapData(100,100,true,0);
            bdp2.draw(getstar(50),new Matrix(1,0,0,1,50,50));
    
            bd2=new Bitmap(bdp2);
            this.addChild(bd2);
            
            this.addEventListener(Event.ENTER_FRAME,onMouseMove)
        }
        
        private function onMouseMove(e:Event):void
        {
            bd2.x=mouseX-50;
            bd2.y=mouseY-50;
             
            if(bd1.bitmapData.hitTest(new Point(bd1.x,bd1.y),1,bd2.bitmapData,new Point(bd2.x,bd2.y),255))
            {
                bd1.filters=[new GlowFilter];
                bd2.filters=[new GlowFilter];
            }
            else
            {
                bd1.filters=[];
                bd2.filters=[];
            }
            
        }
        
        private function getstar(_r:Number):Sprite
        {
            var _star:Sprite=new Sprite;
            _star.graphics.lineStyle(0);
            _star.graphics.moveTo(_r,0);
            
            for(var i:int=1;i<11;i++)
            {
                var r2:Number=_r;
                
                if(i%2>0)
                {
                    r2=_r/2;
                }
                
                var angle:Number=Math.PI*2/10*i;        
                _star.graphics.lineTo(Math.cos(angle)*r2,Math.sin(angle)*r2);
            }
            
            
            return _star;
        }
        
    }
}