Canvas/31_canva_径向渐变.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')

      // createRadialGradient(x0,y0,r0,x1,y1,r1)
      var grd = ctx.createRadialGradient(400, 400, 100, 400, 400, 500)
      grd.addColorStop(0.0, '#fff') // 添加色标
      grd.addColorStop(0.25, '#0ff') // 添加色标
      grd.addColorStop(0.5, '#f00')
      grd.addColorStop(0.75, '#f0f')
      grd.addColorStop(1.0, '#000')

      ctx.fillStyle = grd; // 赋值
      ctx.fillRect(0, 0, 800, 800)
    }
  </script>
</body>

</html>