Canvas/20_canvas_绘制五角星_lineJoin.html

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <title>Page Title</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
</head>

<body>
  <canvas id="myCanvas" style="border:1px solid red;">
    当前浏览器不支持canvas，请更换浏览器后再试
  </canvas>
  <script>
    window.onload = function () {
      var canvas = document.getElementById('myCanvas')

      canvas.width = 800
      canvas.height = 800

      var ctx = canvas.getContext('2d')

      ctx.lineWidth = 10
      // ctx.lineJoin = 'bevel' // 设置线条连接样式，默认miter尖角,bevel斜接,round圆角
      ctx.lineJoin = 'miter' // 设置线条连接样式，默认miter尖角,bevel斜接,round圆角
      ctx.miterLimit = 10 // 尖角阈值，默认10；当lineJoin为miter时，显示尖角的一个阈值，当超过此阈值会转而用bevel绘制连接样式。一般此值不修改
      drawStar(ctx, 10, 300, 400, 400, 30) // 此时，超过阈值，连接处采用bevel绘制，可调整miterLimit
    }

    function drawStar(ctx, r, R, x, y, rot) {
      ctx.beginPath()
      for (var i = 0; i < 5; i++) {
        ctx.lineTo(Math.cos((18 + i * 72 - rot) / 180 * Math.PI) * R + x,
          -Math.sin((18 + i * 72 - rot) / 180 * Math.PI) * R + y)
        ctx.lineTo(Math.cos((54 + i * 72 - rot) / 180 * Math.PI) * r + x,
          -Math.sin((54 + i * 72 - rot) / 180 * Math.PI) * r + y)
      }
      ctx.closePath()

      ctx.stroke()
    }

  </script>
</body>

</html>