index.html
<!DOCTYPE HTML> <html style="height:100%"> <head> <title>canvas基础</title> <meta charset="utf-8"/> <script src="canvas_demo.js"></script> </head> <body style="height:100%"> <canvas id="canvas"> 请升级浏览器 </canvas> </body> </html>
canvas_demo.js
var canvas=document.getElementById("canvas");
var context=canvas.getContext("2d");
canvas.width=document.body.clientWidth;
canvas.height=document.body.clientHeight;
context.beginPath()
context.moveTo(0,0);
context.lineTo(500,500);
context.lineWidth=5;
context.closePath()
context.strokeStyle="red";
context.stroke();
context.beginPath()
context.arc(500,200,150,0,2*Math.PI,true);
context.closePath()
context.strokeStyle="blue";
context.stroke();
context.beginPath()
context.moveTo(800,200)
context.lineTo(1200,100)
context.lineTo(1400,500)
context.closePath()
context.fill()
context.fillRect(1400,300,100,100)
context.beginPath()
context.moveTo(1400,100)
context.lineTo(1600,400)
context.closePath()
var gnt1=context.createLinearGradient(1400,100,1600,400)
gnt1.addColorStop(0,‘red‘)
gnt1.addColorStop(1,‘yellow‘)
context.strokeStyle=gnt1
context.stroke()
var gnt2=context.createLinearGradient(100,0,300,0)
gnt2.addColorStop(0,‘green‘)
gnt2.addColorStop(0.5,‘red‘)
gnt2.addColorStop(1,‘yellow‘)
context.fillStyle=gnt2
context.fillRect(100,600,200,100)
context.beginPath()
context.arc(600,800,100,0,1.5*Math.PI,true)
context.closePath()
context.stroke()
var gtn=context.createRadialGradient(1200,600,50,1200,700,200)
gtn.addColorStop(1,"blue")
gtn.addColorStop(0,"red")
context.fillStyle=gtn
context.fillRect(1000,500,400,400)
原文：http://www.cnblogs.com/xyws/p/5157956.html