代码示例:(标识:eg_html5_canvas_circle)
<!DOCTYPE HTML>
<html>
<body>

<canvas id="myCanvas" width="200" height="100" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
</canvas>

<script type="text/javascript">

var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
cxt.fillStyle="#FF0000";
cxt.beginPath();
cxt.arc(70,18,15,0,Math.PI*2,true);
cxt.closePath();
cxt.fill();

</script>

</body>
</html>
运行结果: