[ActionScript 3.0] 创建倒影

package 
{
    import flash.display.Bitmap;
    import flash.display.BitmapData;
    import flash.display.DisplayObject;
    import flash.display.GradientType;
    import flash.display.Loader;
    import flash.display.Shape;
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.geom.Matrix;
    import flash.geom.Point;
    import flash.net.URLRequest;

    /**
      * ...
      * @author Frost.Yen
      */
    [SWF(width=800, height=1000, backgroundColor=0x000000, frameRate=30)]
    public class Reflection extends Sprite
    {
        private var ldr:Loader=new Loader();
        private var pic:Sprite=new Sprite();
        public function Reflection()
        {
            ldr.load(new URLRequest("http://hiphotos.baidu.com/frostyen/pic/item/7e49d8b53f6b48ffd9335aa2.jpg"));
            ldr.contentLoaderInfo.addEventListener(Event.COMPLETE, onImageLoaded);
        }

        private function onImageLoaded(e:Event):void
        {
            this.addChild(pic);
            pic.addChild(ldr);
            pic.x = 200;
            pic.y = 10;
            ldr.scaleX = ldr.scaleY = .5;
            createRef(pic,5,0);
        }
        /**
           *
           * @param obj  需创建倒影的对象
           * @param distance  对象与倒影的距离
           * @param offset  倒影的偏移量
           */
        private function createRef(obj:DisplayObject,distance:Number=5,offset:Number=0):void
        {
            // 倒置
            var bd:BitmapData = new BitmapData(obj.width,obj.height,true);
            var mtx:Matrix = new Matrix();
            mtx.d = -1;
            mtx.ty = bd.height;
            bd.draw(obj, mtx);

            // 添加倒影渐变
            var _width:int = bd.width;
            var _height:int = bd.height;

            mtx.createGradientBox(_width, _height, 0.5 * Math.PI,0,offset );
            var shape:Shape = new Shape();
            shape.graphics.beginGradientFill(GradientType.LINEAR, [0,0,0], [0.6,0.1, 0], [0,200, 255], mtx);
            shape.graphics.drawRect(0, 0, _width, _height);
            shape.graphics.endFill();
            var mask_bd:BitmapData = new BitmapData(_width,_height,true,0);
            mask_bd.draw(shape);
            // 生成最终效果
            bd.copyPixels(bd, bd.rect, new Point(0, 0), mask_bd, new Point(0, 0), false);
            // 将倒影放置于对象下方
            var ref:Bitmap = new Bitmap(bd);
            ref.y = obj.height + obj.y + distance;
            ref.x = obj.x;
            obj.parent.addChild(ref);
        }
    }

}