canvas一周一练 -- canvas绘制太极图（6）
运行效果：
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<canvas id="drawing" width="600" height="600">A drawing of someing!</canvas>
<script type="text/javascript">
var drawing = document.getElementById('drawing');
if(drawing.getContext) {
//绘制太极图
var context = drawing.getContext('2d');
context.fillStyle = 'Lavender';
context.fillRect(0, 0, 600, 400);
//画外面的两个大半圆
context.fillStyle = '#000';
context.beginPath();
context.arc(200, 200, 180, 0.5*Math.PI, 1.5*Math.PI, false);
context.closePath();
context.fill();
context.fillStyle = '#fff';
context.beginPath();
context.arc(200, 200, 180, 1.5*Math.PI, 0.5*Math.PI, false);
context.closePath();
context.fill();
//画里面的两个小半圆
context.beginPath();
context.arc(200, 110, 90, 0.5*Math.PI, 1.5*Math.PI, false);
context.closePath();
context.fill();
context.fillStyle = '#000';
context.beginPath();
context.arc(200, 290, 90, 1.5*Math.PI, 0.5*Math.PI, false);
context.closePath();
context.fill();
//画里面的两个小圆
context.beginPath();
context.arc(200, 110, 20, 0, 2*Math.PI, false);
context.closePath();
context.fill();
context.fillStyle = '#fff';
context.beginPath();
context.arc(200, 290, 20, 0, 2*Math.PI, false);
context.closePath();
context.fill();
}
</script>
</body>
</html>
