<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript">
function draw(id){
var canvas = document.getElementById(id);
if(canvas == null){
return false;
}
var context = canvas.getContext(‘2d‘);
context.fillStyle = "#eeeeff";
context.fillRect(0,0,400,300);
var dx = 150;
var dy = 150;
var s = 100;
context.beginPath();
context.globalCompositeOperation = ‘and‘;
context.fillStyle = ‘rgb(100,255,100)‘;
context.strokeStyle = ‘rgb(0,0,100)‘;
var x = Math.sin(0);
var y = Math.cos(0);
var dig = Math.PI/15*11;
for(var i=0;i<30;i++){
var x = Math.sin(i*dig);
var y = Math.cos(i*dig);
context.bezierCurveTo(dx+x*s,dy+y*s-100,dx+x*s+100,dy+y*s,dx+x*s,dy+y*s);
}
context.closePath();
context.fill();
context.stroke();
}
</script>
</head>
<body onload="draw(‘canvas‘);">
<canvas id="canvas" width="400" height="300"></canvas>
</body>
</html>
原文：http://www.cnblogs.com/staven/p/4764619.html