Flex毛玻璃效果

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" clipContent="true" verticalScrollPolicy="off" horizontalScrollPolicy="off"
width="100%" height="100%" horizontalAlign="center" verticalAlign="middle" backgroundColor="#FFFFFF"
creationComplete="onCreationComplete(event)" mouseUp="onMouseUp(event)" mouseMove="onMouseMove(event)">
<mx:Script source="FrostedGlass.as"/>
<mx:Container id="ctlContainer" x="0" y="0" width="100%" height="100%"
clipContent="true" horizontalScrollPolicy="off" verticalScrollPolicy="off">
<mx:Image horizontalAlign="center" id="ctlImage" x="0" y="0" width="1024" height="768" maintainAspectRatio="true"
source="@Embed(source='images/bg.jpg')"
/>
</mx:Container>
<mx:Box borderStyle="solid" borderThickness="1"
borderColor="#000000" render="onBoxRender(event)"
x="200" y="200" height="200" width="400" id="ctlBox"
filters="{[new DropShadowFilter(5,45,0x000000,0.5)]}"
mouseDown="onMouseDown(event)" />
</mx:Application>

// ActionScript file
import flash.display.BitmapData;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.filters.BlurFilter;
import flash.geom.Matrix;
import flash.geom.Point;
import flash.geom.Rectangle;
private var m_mouseDown : Boolean = false;
private var m_offsetPt : Point;
private function onCreationComplete(evt:Event) : void
{
onBoxRender(null);
}
private function onBoxRender(evt:Event) : void
{
if( ctlContainer.width > 0 && ctlContainer.height > 0 )
{
var bmpData : BitmapData = new BitmapData( ctlContainer.width,ctlContainer.height,false);
var matrix : Matrix = new Matrix();

// 对矩阵进行平移变换
matrix.translate( -1 * ctlBox.x,-1 * ctlBox.y);

// 将背景填充到移动元件上来
bmpData.draw( ctlContainer
,matrix
,null
,new Rectangle( 0,ctlBox.width + 4,ctlBox.height + 4) // 裁剪区域
);
bmpData.applyFilter( bmpData
,bmpData.width,bmpData.height)
,new Point( 0,0)
,new BlurFilter( 5,5,5) // BlurFilter的参数越大计算量越大 移动的时候越卡
);
ctlBox.graphics.beginBitmapFill(bmpData,null,false,false);
ctlBox.graphics.drawRect( 0,ctlBox.width,ctlBox.height);
ctlBox.graphics.endFill();
}
}
private function onMouseDown(evt:MouseEvent) : void
{
m_mouseDown = true;
m_offsetPt = new Point( ctlBox.mouseX,ctlBox.mouseY);
}
private function onMouseUp(evt:MouseEvent) : void
{
m_mouseDown = false;
evt.updateAfterEvent();
}
private function onMouseMove(evt:MouseEvent) : void
{
if( m_mouseDown )
{
ctlBox.x = evt.stageX - m_offsetPt.x;
ctlBox.y = evt.stageY - m_offsetPt.y;
evt.updateAfterEvent();
}
}