1、线性渐变：

  1. <style>
  2.     canvas {
  3.         width: 500px;
  4.         height: 300px;
  5.         border: 1px solid;
  6.     }
  7. </style>
  8. </head>
  9. <body>
  10. <canvas id="can" width="500px" height="300px"></canvas>
  11. <script>
  12.     var canvas = document.getElementById("can");
  13.     var ctx = canvas.getContext("2d");
  15.    ctx.beginPath();
  16.    //线性渐变的起始点是坐标系的原点，而不是矩形的原点
  17.    var bg = ctx.createLinearGradient(0,0,200,0);//线性渐变，设两个点
  18.    bg.addColorStop(0,"white");//只有0~1
  19.    bg.addColorStop(0.5,"blue");
  20.    bg.addColorStop(1,"black");
  21.    ctx.fillStyle = bg;
  22.    ctx.fillRect(0,0,200,100);
  23. </script>
  24. </body>