用AS把位图切割成三角形

import flash.display.BitmapData;
import flash.geom.Matrix;
this.createEmptyMovieClip("mShape",1);
this.createEmptyMovieClip("mBitmap",2);
mShape._x=100;
mShape._y=200;
var oListener:Object =new Object();
oListener.onLoadInit=function(mClip:MovieClip):Void{
        var bmpImage:BitmapData =new BitmapData(mClip._width,mClip._height)
        bmpImage.draw (mClip,new Matrix());
        mClip._visible=false;
        mShape.lineStyle(1);
        mShape.beginBitmapFill(bmpImage,false,true,true);
        //mShape.curveTo(100,-50,200,0);
        mShape.lineTo(200,100);
        mShape.lineTo(0,100);
        mShape.lineTo(0,0);
        mShape.endFill();
        }
        var mlBitmap:MovieClipLoader=new MovieClipLoader();
        mlBitmap.addListener(oListener);
        mlBitmap.loadClip("/UploadTeach/200707/20070730122301909.jpg",mBitmap)