<html>
<body>
<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
您的浏览器不支持 HTML5 canvas 标签。</canvas>
<script>
var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
var grd=ctx.createLinearGradient(0,0,170,0);
grd.addColorStop(0,"black");
grd.addColorStop(0.5,"red");
grd.addColorStop(1,"white");
ctx.fillStyle=grd;
ctx.fillRect(20,20,150,100);
</script>
</body>
</html>