用h5中的canvas 绘制八卦图

 1 <!doctype html>
 2 <html>
 3  <head>
 4   <meta charset="UTF-8">
 5   <title>canvas绘制八卦图</title>
 6  </head>
 7 
 8  <body>
 9   <canvas id="canvas" width="600" height="500"></canvas>
10   <script>
11     var canvas=document.getElementById("canvas");
12     var context=canvas.getContext('2d');
13     
14     //1.先绘制一个完整的空心圆
15     context.beginPath();
16     context.arc(250,250,200,0,Math.PI*2);
17     context.stroke();
18 
19     //2.绘制半黑半白  默认为黑色
20     context.beginPath();
21     context.arc(250,250,200,Math.PI*3/2,Math.PI/2,true);
22     context.fill();
23 
24     //3.绘制一黑一白两个半圆
25     context.fillStyle="white";
26     context.beginPath();
27     context.arc(250,150,100,0,Math.PI*2);
28     context.fill();
29 
30     context.fillStyle="black";
31     context.beginPath();
32     context.arc(250,350,100,0,Math.PI*2);
33     context.fill();
34     
35     //4.绘制两个小圆
36     context.fillStyle="black";
37     context.beginPath();
38     context.arc(250,150,30,0,Math.PI*2);
39     context.fill();
40 
41     context.fillStyle="white";
42     context.beginPath();
43     context.arc(250,350,30,0,Math.PI*2);
44     context.fill();
45   </script>
46  </body>
47 </html>

效果图:

原文地址:http://www.cnblogs.com/--silence/p/4999061.html

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