注意要根据你电脑的实际情况量力而行
要是随机渲染2000个的话，就会是这钟情况
你的浏览器就会几秒钟之后失去响应，GG。
一般渲染个200个就很炫酷了
效果如下
代码如下
<!DOCTYPE html>
<html>
<head>
<title>背景滚动</title>
<meta charset="utf-8">
<style>
body {
background: #dddddd;
}
#canvas {
position: absolute;
top: 30px;
left: 10px;
background: #ffffff;
cursor: crosshair;
margin-left: 10px;
margin-top: 10px;
-webkit-box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
-moz-box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
}
input {
margin-left: 15px;
}
</style>
</head>
<body>
<canvas id='canvas' width='1024' height='512'>
Canvas not supported
</canvas>
<input id='animateButton' type='button' value='Animate'/>
<script src='./js/requestNextAnimationFrame.js'></script>
</body>
</html>
<script type="text/javascript">
var canvas=document.getElementById("canvas")
var context=canvas.getContext("2d")
var Sprite=function(name,painter,behaviors){
if(name!==undefined){this.name=name}
if(painter!==undefined){this.painter=painter}
this.top=0
this.left=0
this.width=0
this.height=0
this.velocityX=0
this.velocityY=0
this.visible=true
this.animating=false
this.behaviors=behaviors||[]
this.RADIUS=0
return this
}
Sprite.prototype={
paint:function(context){
if(this.painter!==undefined&&this.visible){this.painter.paint(this,context)}
},
update:function(context,time){
for(var i=0;i<this.behaviors.length;i++){
this.behaviors[i].excute(this,context,time)
}
}
}
// var RADIUS=5
var pai={
paint:function(sprite,context){
context.save()
context.beginPath()
sprite.left=sprite.left+sprite.velocityX
sprite.top=sprite.top+sprite.velocityY
if(sprite.left+sprite.RADIUS>canvas.width||sprite.left-sprite.RADIUS<0){
sprite.velocityX=-sprite.velocityX
}
if(sprite.top+sprite.RADIUS>canvas.height||sprite.top-sprite.RADIUS<0){
sprite.velocityY=-sprite.velocityY
}
context.arc(sprite.left+sprite.width/2,sprite.top+sprite.height/2,sprite.RADIUS,0,Math.PI*2,false)
context.clip()
context.shadowBlur=8
context.lineWidth=2
context.strokeStyle="rgb(100,100,195)"
context.fillStyle="rgba(30,144,255,0.15)"
context.fill()
context.stroke()
context.restore()
}
}
var star_list=[]
for(var i=0;i<100;i++){
var star=new Sprite("star"+i,pai)
star.left=parseInt(19+(Math.random()*800))
star.top=parseInt(19+(Math.random()*450))
if(i%2==0){
star.velocityY=parseInt(Math.random()*15+1)
star.velocityX=parseInt(Math.random()*15+1)
}else{
star.velocityY=-(parseInt(Math.random()*15+1))
star.velocityX=-(parseInt(Math.random()*15+1))
}
star.RADIUS=parseInt(Math.random()*20+1)
star_list.push(star)
}
function animate(){
context.clearRect(0,0,canvas.width,canvas.height)
context.fillStyle="rgb(0,0,0)"
context.fillRect(0,0,canvas.width,canvas.height)
for(var i=0;i<star_list.length;i++){
star_list[i].paint(context)
}
window.requestAnimationFrame(animate)
}
window.requestAnimationFrame(animate)
</script>
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