Flex4 调用摄像头拍照

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
			   xmlns:s="library://ns.adobe.com/flex/spark"
			   xmlns:mx="library://ns.adobe.com/flex/mx"
			    width="500" height="350" creationComplete="application1_creationCompleteHandler(event)">
	<fx:Script>
		<![CDATA[
			import mx.controls.Alert;
			import mx.events.CloseEvent;
			import mx.events.FlexEvent;
			import mx.graphics.codec.PNGEncoder;
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			private const CAMERA_WIDTH:int=400;
			private const CAMERA_HEIGHT:int=300;
			private var _camera:Camera;
			private var _pngEn:PNGEncoder;
			private var _bitmapData:BitmapData;
			private var _fr:FileReference;
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			protected function application1_creationCompleteHandler(event:FlexEvent):void
			{
				_pngEn=new PNGEncoder;
				_fr=new FileReference;
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				checkCamera();
			}
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			private function checkCamera(event:CloseEvent=null):void
			{
				_camera=Camera.getCamera();
				if(_camera!=null){
					_camera.setMode(400,300,24);
					_camera.setQuality(0,100);
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					cameraDisplay.attachCamera(_camera);
					cutCameraBtn.enabled=true;
				}else{
					Alert.okLabel="重试";
					Alert.show("找不到摄像头，程序将重新查找","对不起",4,null,checkCamera);
				}
			}
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			private function getDateString():String{
				var date:Date=new Date;
				return "拍照"+date.getFullYear()+(date.getMonth()+1)+date.getDate()+date.getHours()+date.getMinutes()+date.getSeconds()+date.getMilliseconds();
			}
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			protected function cutCameraBtn_clickHandler(event:MouseEvent):void
			{
				_bitmapData=new BitmapData(CAMERA_WIDTH,CAMERA_HEIGHT);
				_bitmapData.draw(cameraDisplay);
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				var bytes:ByteArray=_pngEn.encode(_bitmapData);
				_fr.save(bytes,getDateString()+".png");
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				//release
				bytes.length=0;
				_bitmapData.dispose();
			}
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		]]>
	</fx:Script>
	<fx:Declarations>
		<!-- 将非可视元素（例如服务、值对象）放在此处 -->
	</fx:Declarations>
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	<mx:VideoDisplay id="cameraDisplay"
					 width="400"
					 height="300"
					 y="10"
					 x="50"/>
	<mx:Button id="cutCameraBtn"
			   label="拍照"
			   click="cutCameraBtn_clickHandler(event)"
			   enabled="false"
			   x="227"
			   y="318"/>
</s:Application>

?? 图片保存为png格式