canvas 制作八卦图

Posted on 2019-09-15 15:35  牛顿8848  阅读(182)  评论(0)  编辑  收藏  举报

效果

 

 注意图中几个圆形

<!doctype html>
<html>
   <head>
      <meta charset="UTF-8">
      <title>canvas绘制八卦图</title>
   </head>
   <style>
   #canvas{
       position: relative;
       left: 300px;
   }
   </style>
<body>
    <canvas id="canvas" width="600" height="500"></canvas>
    <script>
        var canvas=document.getElementById("canvas");
        var context=canvas.getContext('2d');
 
        //1.先绘制一个完整的空心圆
        context.beginPath();
        context.arc(250,250,200,0,Math.PI*2);
        context.stroke();
    
        //2.绘制半黑半白  默认为黑色
        context.beginPath();
        context.arc(250,250,200,Math.PI*3/2,Math.PI/2,true);
        context.fill();

        //3.绘制一黑一白两个半圆
        context.fillStyle="white";
        context.beginPath();
        context.arc(250,150,100,0,Math.PI*2);
        context.fill();
    
        context.fillStyle="black";
        context.beginPath();
        context.arc(250,350,100,0,Math.PI*2);
        context.fill();
        
        //4.绘制两个小圆
        context.fillStyle="black";
        context.beginPath();
        context.arc(250,150,30,0,Math.PI*2);
        context.fill();
    
        context.fillStyle="white";
        context.beginPath();
        context.arc(250,350,30,0,Math.PI*2);
        context.fill();
    </script>
</body>
</html>