使用BITMAPDATA制作残影效果

 在MC运动的过程中，先对MC加入滤镜，然后建立一个bitmapdata进行绘制，踪迹由于colorTransform进行递减而消失。

 

//实现1

import flash.events.Event;

var radius = 5;

var particle = new Sprite();

particle.graphics.lineStyle(2,0xffffff);

particle.graphics.beginFill(0xffffff,0.8);

particle.graphics.drawCircle(-radius,-radius,2 * radius);

particle.graphics.endFill();

this.addChild(particle);

 

var bitmapData = new BitmapData(this.stage.stageWidth,this.stage.stageHeight,true,0x00000000);

var bitmap = new Bitmap(bitmapData);

this.addChild(bitmap);

var blur = new BlurFilter(2,1);

var colorTransform = new ColorTransform(0.9,0.95,0.9,1);

var origin = new Point(0,0);

 

 

this.addEventListener(Event.ENTER_FRAME,onFrame);

var speed:int=1;

var angle=0;

function onFrame(e:Event):void

{

angle+=10;

particle.x=100*Math.sin(angle/180)+200;

particle.y=100*Math.cos(angle/180)+200;

//在绘制新的图像之前应用滤镜到旧的图像。 

bitmapData.applyFilter(bitmapData,bitmapData.rect,origin,blur);

bitmapData.colorTransform(bitmapData.rect, colorTransform);

bitmapData.draw(this.stage);

}

 

//实现2

 

//用了bitmapData的colorTransform函数。在每次渲染时都对bitmapData的颜色和alpha通道做递减运算。

var bmp:Bitmap = new Bitmap();

var bmd:BitmapData = new BitmapData(550, 400, false, 0);

var rect:Rectangle = new Rectangle(0, 0, 550, 400);

var cTra:ColorTransform = new ColorTransform(0, .8, .8, .9);

var xp:int = 0;

var yp:int = 0;

bmp.bitmapData = bmd;

addChild(bmp);

stage.addEventListener(Event.ENTER_FRAME, enterFrameHandler);

function enterFrameHandler(event:Event):void {

    bmd.colorTransform(rect, cTra);

    xp += (mouseX - xp) / 5;

    yp += (mouseY - yp) / 5;

    bmd.fillRect(new Rectangle(xp, yp, 10, 10), 0xffffff);

}