【代码片段】Bitmap & BitmapData

package
{
	import flash.display.Bitmap;
	import flash.display.BitmapData;
	import flash.display.Sprite;
	import flash.display.StageAlign;
	import flash.display.StageScaleMode;
	import flash.geom.Rectangle;
	
	public class test extends Sprite
	{
		public function test()
		{
			stage.align = StageAlign.TOP_LEFT;
			stage.scaleMode = StageScaleMode.NO_SCALE;
			//画一组随机的线条;
			graphics.lineStyle(0);
			for(var i:int = 0;i<100;i++)
			{
			graphics.lineTo(Math.random()*300,Math.random()*400);
			}
			//创建一个不透明位图
			var bmpd1:BitmapData = new BitmapData(300,200,false,0xffffff);
			bmpd1.fillRect(new Rectangle(100,50,100,100),0xff0000);
			var bmp1:Bitmap = new Bitmap(bmpd1);
			addChild(bmp1);
			//创建一个透明位图
			var bmpd2:BitmapData = new BitmapData(300,200,true,0x00fffff);
			bmpd2.fillRect(new Rectangle(100,50,100,100),0x80ff0000);
			var bmp2:Bitmap = new Bitmap(bmpd2);
			bmp2.y = 200;
			addChild(bmp2);
		}
	}
}

显示效果：上方一个红色的方块，下方为一组随机线条（不断线），透明的红色方块浮在线条上方