<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>html5 Canvas动画旋转的小方块；</title>
<link rel="stylesheet" href="">
</head>
<body>
<script>
window.onload=function(){
var canvas = document.querySelector("canvas");
canvas.width = canvas.height = 500
canvas.style.background = "red"
if (canvas.getContext) {
var ext = canvas.getContext("2d");
var num = 0;
var scale=0;
var value=0
ext.fillStyle = "#f90";
ext.translate(canvas.width / 2, canvas.height / 2);
function rotate() {
ext.clearRect(-canvas.width / 2, -canvas.height / 2, canvas.width, canvas.height)
num++;
if(scale==100){
value=-1;
}else if(scale==0){
value=1
}
scale+=value
ext.save();
ext.rotate(num * Math.PI / 180)
ext.scale(scale*1/50,scale*1/50)
console.log(scale);
ext.translate(-50, -50)
ext.fillRect(0, 0, 100, 100);
ext.restore();
}
var t=setInterval(rotate,30);
canvas.onmouseover=function(){
clearInterval(t);
}
canvas.onmouseout=function(){
t=setInterval(rotate,30);
}
}
}
</script>
<canvas></canvas>
</body>
</html>
DEMO地址：http://codepen.io/jonechen/pen/xVbPLJ
