8.18.比较两幅位图

<mx:VBox xmlns:mx="http://www.adobe.com/2006/mxml" width="400"
height="800">
<mx:Script>
<![CDATA[
import mx.core.BitmapAsset;
private function compare():void {
var bmpd1:BitmapData = new BitmapData(img1.width,img1.height);
var bmpd2:BitmapData = new BitmapData(img2.width,img2.height);
bmpd1.draw(img1)
bmpd2.draw(img2);
var diff:BitmapData = bmpd2.compare(bmpd1) as BitmapData;
var bitmapAsset:BitmapAsset = new BitmapAsset(diff);
img3.source = bitmapAsset;
}

]]>
</mx:Script>
<mx:Image id="img1" source="../assets/mao.jpg" height="200"
width="200"/>
<mx:Image id="img2" source="../assets/bigshakey.png"
height="200" width="200"/>
<mx:Button click="compare()" label="compare"/>
<mx:Image id="img3"/>
</mx:VBox>