<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<canvas id="canvas" style="margin:0 auto;border:1px #ddd solid;">
The current browser does not support Canvas, can replace the browser a try!
</canvas> <script> window.onload = function(){
var canvas = document.getElementById('canvas'); canvas.width = 800;
canvas.height = 800; if(canvas.getContext('2d')){
var context = canvas.getContext('2d'); // begin
var linearGrad = context.createLinearGradient(0,0,200,800);
linearGrad.addColorStop(0.0,'white');
linearGrad.addColorStop(0.25,'yellow');
linearGrad.addColorStop(0.5,'green');
linearGrad.addColorStop(0.75,'blue');
linearGrad.addColorStop(1.0,'black');
context.fillStyle = linearGrad;
context.fillRect(0,0,800,800) }else{
alert('当前游览器不支持Canvas，请更换游览器后再试！');
}
}
</script>
</body>
<script>
/*总结
step 1
//修改xstart,ystart,xend,yend 改变渐变方向
//修改fillRect 改变渐变区域
var grd = context.creatLinearGradient(xstart,ystart,xend,yend)
step 2
//stop的值域[0,1]
grd.addColorStop(stop,color)
*/
</script>
</html>