代码实例：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<style>
canvas{
background:#eee;
}
</style>
<title>星星</title>
<meta charset="utf-8">
<script>
window.onload=function () {
var canvas=document.getElementById("canvas");
var cobj=canvas.getContext("2d");
var starArr=[];
for (var i=0; i<30; i++) {
var starObj={
radius1:20+10*Math.random(),radius2:8+7*Math.random(),x:30+(canvas.width-60)*Math.random(),y:30+(canvas.height-60)*Math.random(),num:Math.ceil(4+4*Math.random()),color:"rgb("+parseInt(255*Math.random())+","+parseInt(255*Math.random())+","+parseInt(255*Math.random())+")",angle:360*Math.random(),changeAngle:-5+10*Math.random()
}
starArr.push(starObj);
}
setInterval(function () {
cobj.clearRect(0,0,500,500);
for (var i=0; i<starArr.length; i++) {
starArr[i].angle+=starArr[i].changeAngle;
cobj.save();
cobj.beginPath();
cobj.translate(starArr[i].x,starArr[i].y);
cobj.rotate(starArr[i].angle*Math.PI/180);
cobj.scale(Math.sin(starArr[i].angle*Math.PI/180),Math.sin(starArr[i].angle*Math.PI/180))
cobj.globalAlpha=Math.abs(Math.sin(starArr[i].angle*Math.PI/180));
drawStar (0,0,starArr[i].radius1,starArr[i].radius2,starArr[i].num,"fill",starArr[i].color);
cobj.restore();
}
},60)
function drawStar (x,y,radius1,radius2,num,drawType,color) {
var angle=360/(num*2);
var arr=[];
for (var i=0; i<num*2; i++) {
var starObj={};
if(i%2==0){
starObj.x=x+radius1*Math.cos(i*angle*Math.PI/180);
starObj.y=y+radius1*Math.sin(i*angle*Math.PI/180);
}else{
starObj.x=x+radius2*Math.cos(i*angle*Math.PI/180);
starObj.y=y+radius2*Math.sin(i*angle*Math.PI/180);
}
arr.push(starObj);
}
cobj.beginPath();
cobj.fillStyle=color;
cobj.strokeStyle=color;
cobj.moveTo(arr[0].x,arr[0].y);
for (var i=1; i<arr.length; i++) {
cobj.lineTo(arr[i].x,arr[i].y);
}
cobj.closePath();
if(drawType=="fill"){
cobj.fill();
}else{
cobj.stroke();
}
}
}
</script>
</head>
<body>
<canvas id="canvas" width=500 height=500>
</canvas>
</body>
</html>
效果：
