html <canvas>标签的使用

xidaojia2015

发布于
2015-11-05

更新于
2015-11-05

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
body{
    background:black;
}
#c1{
    background:white;
}
span{
    color:white;
}
</style>
<script>
window.onload=function() {
    var oC = document.getElementById("c1") ;   
    var oGC = oC.getContext('2d') ;    
    var num = 0;
    
    oGC.translate(100,100);
    
    setInterval(function(){
        num++;
        
        oGC.save();
        oGC.clearRect(0,0,oC.width,oC.height);
        oGC.rotate(num*Math.PI/180);    
        oGC.fillRect(0,0,100,100);
        oGC.restore();

        },30);
     
}
</script>
</head>

<body>
<canvas id="c1"  width="400" height="400">    
   <span>不支持canvas浏览器</span>
</canvas>
</body>
</html>

做了一个以坐标(100,100)为中心点旋转的小方块，显示效果不正常，请各位老师指教哪里有错误，谢谢！

html5