Flex 图片缩放、托拽效果 Zoom版

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"  
    layout="absolute"     width="1014" height="590" applicationComplete="app(event)" horizontalScrollPolicy="off" verticalScrollPolicy="off" verticalAlign="middle" horizontalAlign="center">
    <mx:Script>
        <![CDATA[
            import mx.events.EffectEvent;
            import mx.controls.Alert;
            import mx.events.FlexEvent;
            protected function app(event:FlexEvent):void
            {
            img.addEventListener(MouseEvent.MOUSE_DOWN, imgMouseDown);
            img.addEventListener(MouseEvent.MOUSE_UP, imgMouseUp);
            this.addEventListener(MouseEvent.MOUSE_WHEEL, imgZoom);
            }
            private function imgMouseDown(evt:MouseEvent):void
            {
                evt.currentTarget.startDrag();
            }
            private function imgMouseUp(evt:MouseEvent):void
            {
                evt.currentTarget.stopDrag();
            }
            private function imgZoom(evt:MouseEvent):void
            {
                var w:Number = evt.delta;
                var z:Number = fd.zoomHeightTo;
                if(w > 0 && z < 3)
                {
                    fd.stop();
                    fd.zoomHeightTo +=0.1;
                    fd.zoomWidthTo +=0.1;
                    fd.play();
                }
                if(w < 0 && z > 0.2)
                {
                    fd.stop();
                    fd.zoomHeightTo -=0.1;
                    fd.zoomWidthTo -=0.1;
                    fd.play();
                }

            }
            
        ]]>
    </mx:Script>
    <mx:Image y="123" id="img" source="1.jpg" x="257"/>
    <mx:Zoom id="fd" target="{img}"  zoomHeightTo="1"  zoomWidthTo="1" duration="600"/>  

</mx:Application>