详细代码：
/***Flash CS4 ActionScript 3.0
*这里呈现粒子基本技术的一个动画实例。当它到处移动时，运动的粒子在它后面
*留下了一个彗星的痕迹。这是因为粒子正在绘制到从不被抹掉的一个位图。
*滤镜应用到位图导致旧的图像慢慢地褪色离开，新的图像在顶端上绘制。
*/
package {
import flash.display.Sprite;
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.events.Event;
import flash.geom.Point;
import flash.filters.BlurFilter;
import flash.geom.ColorTransform;
import flash.display.Shape;
[SWF(width = "420", height = "320", backgroundColor = "0xffffff", frameRate = "30")];
public class Main extends Sprite {
private var particle:Sprite;
private var bitmapData:BitmapData;
private var bitmap:Bitmap;
private var velX:Number;
private var velY:Number;
private var radius:Number;
private var displayWidth:Number;
private var displayHeight:Number;
private var display:Sprite;
private var origin:Point;
private var blur:BlurFilter;
private var colorTransform1:ColorTransform;
private var colorTransform2:ColorTransform;
private var randomAccel:Number;
private var maxVelX:Number;
private var maxVelY:Number;
private var margin:Number;
public function Main():void {
init();
}
private function init():void {
radius = 5;
margin = radius + 2;
particle = new Sprite();
particle.graphics.lineStyle(2,0xffffff);
particle.graphics.beginFill(0xffffff,0.5);
particle.graphics.drawEllipse(-radius,-radius,2 * radius,2 * radius);
particle.graphics.endFill();
//设定一个开始的位置
particle.x = 50;
particle.y = 40;
display = new Sprite();
display.addChild(particle);
//运动的参数
velX = 1;
velY = 1.3;
randomAccel = 0.3;
maxVelX = 6;
maxVelY = 6;
//位图的大小：
displayWidth = 400;
displayHeight = 300;
//见到的位图：
bitmapData = new BitmapData(displayWidth,displayHeight,true,0x00000000);
bitmap = new Bitmap(bitmapData);
//绘制边框
var frame:Shape = new Shape();
frame.graphics.lineStyle(1,0x333333);
frame.graphics.drawRect(-0.5,-0.5,displayWidth + 1,displayHeight + 1);
//BlurFilter滤镜
blur = new BlurFilter(4,4);
colorTransform1 = new ColorTransform(0.999,0.95,0.9,1);
origin = new Point(0,0);
/*
这里是颜色变换改为那一个在上面。它应用透明度衰减和颜色变化。改变代 码在 onEnter 结束的时候动作，以便改为使用 colorTransform 2 。
*/
colorTransform2 = new ColorTransform(0.999,0.95,0.9,0.999);
bitmap.x = frame.x = 10;
bitmap.y = frame.y = 10;
this.addChild(bitmap);
this.addChild(frame);
this.addEventListener(Event.ENTER_FRAME, onEnter);
}
function onEnter(evt:Event):void {
//随机的加速。
velX += randomAccel*(2 * Math.random()-1);
velY += randomAccel*(2 * Math.random()-1);
//
if (velX > maxVelX) {
velX = maxVelX;
}
else if (velX < -maxVelX){
velX = -maxVelX;
}
if (velY > maxVelY) {
velY = maxVelY;
}
else if (velY < -maxVelY) {
velY = -maxVelY;
}
// 移动粒子以及反弹粒子
particle.x += velX;
if (particle.x < margin) {
particle.x = margin;
velX *= -1;
}
else if (particle.x > displayWidth - margin) {
particle.x = displayWidth - margin;
velX *= -1;
}
particle.y += velY;
if (particle.y < margin) {
particle.y = margin;
velY *= -1;
}
else if (particle.y > displayHeight - margin) {
particle.y = displayHeight - margin;
velY *= -1;
}
//在绘制新的图像之前应用滤镜到旧的图像。
//粒子留下的踪迹从不抹掉，它仅仅逐渐地褪色离开。
bitmapData.applyFilter(bitmapData,bitmapData.rect,origin,blur);
bitmapData.colorTransform(bitmapData.rect, colorTransform1);
bitmapData.draw(display);
}
}
}