擦除效果实现，bitmapData数据清除

import flash.display.Sprite;
import flash.display.BlendMode;
import flash.display.BitmapData;
import flash.display.Bitmap;
import flash.events.MouseEvent;
import flash.geom.Matrix;
import flash.geom.ColorTransform;
import flash.text.TextField;
import flash.utils.ByteArray;
import flash.geom.Rectangle;

var mc:Sprite = new mc_link();

var btp:BitmapData = new BitmapData(w, h);
btp.draw(mc);
var bt:Bitmap = new Bitmap(btp);
addChild(bt);

var isDrawing:Boolean;
//定义擦除画笔的宽度
var penW:int = 15;


this.stage.addEventListener(MouseEvent.MOUSE_DOWN, downHandle);
this.stage.addEventListener(MouseEvent.MOUSE_UP, upHandle);
this.stage.addEventListener(MouseEvent.MOUSE_MOVE, moveHandle);


function downHandle(e:MouseEvent):void{
	if(bt.hitTestPoint(this.mouseX, this.mouseY)){
		isDrawing = true;
	}
}
function upHandle(e:MouseEvent):void{
	isDrawing = false;
}
 
function moveHandle(e:MouseEvent):void{
	if(!isDrawing)return;
	
	e.updateAfterEvent();
	
                //擦除原理：使用空数据替换
	var nullBtp:BitmapData = new BitmapData(penW, penW, true, 0x00000000);
	var byteArr:ByteArray = nullBtp.getPixels(nullBtp.rect);
	byteArr.position = 0;
	btp.setPixels(new Rectangle(bt.mouseX, bt.mouseY, penW, penW), byteArr);

　　　　　　//检测是否完全擦除:btp.getColorBoundsRect(0xFF000000,0x00000000,false);
　　　　　　
}

另外一种方法是增加一个容器，在容器上面绘画，然后组合起来，结果可能擦除不干净，并且检测不到是否擦完：

btp.draw(drawMc, new Matrix(), new ColorTransform(), BlendMode.ERASE);