关于js画布的问题,这个为什么画出来是正方形?
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<canvas id="one" width="800" height="800"></canvas>
</body>
</html>
<script type="text/javascript">
var canvas=document.getElementById("one");
var context=canvas.getContext("2d");
context.scale(2,1);
context.rotate(Math.PI/2);
context.fillRect(0,-50,100,50);
</script>