Canvas/13_canvas_封闭图形_填充颜色陷阱.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.beginPath()
      ctx.moveTo(100, 350)
      ctx.lineTo(500, 350)
      ctx.lineTo(500, 200)
      ctx.lineTo(700, 400)
      ctx.lineTo(500, 600)
      ctx.lineTo(500, 450)
      ctx.lineTo(100, 450)

      ctx.closePath()

      ctx.lineWidth = 10
      ctx.stroke() // 先描边

      ctx.fillStyle = 'yellow'
      ctx.fill() // 后填充，会导致填充色覆盖一半lineWidth，正确做法应该是先填充再描边
    }

  </script>
</body>

</html>