html canvas非正方旋转和缩放...写的大多是正方的有人表示一直看正方的看厌了

<!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>非正方形对象的缩放和旋转</title>
<script src="js/modernizr.js"></script>
</head>
 
<body>
<script type="text/javascript">
window.addEventListener('load',eventWindowLoaded,false);
function eventWindowLoaded(){
    canvasApp();
}
function canvasSupport(){
    return Modernizr.canvas;
}
function canvasApp(){
    if(!canvasSupport()){
        return;
    }else{
        var theCanvas = document.getElementById('canvas')
        var context = theCanvas.getContext("2d")
 
    }
    drawScreen();
    function drawScreen(){
         
         
        context.setTransform(1,0,0,1,0,0);
        var angleInRadians = 45 * Math.PI / 180;
        var x = 100;
        var y = 100;
        var width = 100;
        var height = 50;
        context.translate(x+.5*width,y+.5*height);
        context.rotate(angleInRadians);
        context.scale(2,2);
        context.fillStyle="#000";
        context.fillRect(-.5*width,-.5*height,width,height);
         
    }
     
}
 
 
</script>
<canvas id="canvas" width="500" height="500">
你的浏览器无法使用canvas
小白童鞋；你的支持是我最大的快乐！！
</canvas>
</body>
</html>