HTML5之Canvas画正方形

1、设计源码

<!DOCTYPE html>
<head>
<meta charset="utf-8" />
<title>HTML5之Canvas画正方形</title>
<script type="text/javascript">
    function drawFour(id)
	{
		//获取canvas元素
		var canvas = document.getElementById("canvas");
		if(canvas == null)
		   return false;
		//获取上下文
		var context = canvas.getContext('2d');
		//设定填充图形的样式
		context.fillStyle = "#EEEEFF";
		//绘制图形
		context.fillRect(0,0,800,800);
		context.fillStyle = "yellow";
		//设定图形边框的样式
		context.strokeStyle = "blue";
		//指定线宽
		context.lineWidth = 150;
		context.fillRect(50,50,500,500);
		context.strokeRect(50,50,500,500);	
	}
</script>
</head>
<body onLoad="drawFour('canvas')">
   <canvas id="canvas" width="1200" height="560"/>
</body>

2、设计结果

3、分析说明

（1）获取Canvas元素

var canvas = document.getElementById("canvas");

（2）取到上下文

var context = canvas.getContext('2d');

（3）填充绘制边框

context.fillStyle = "#EEEEFF";//填充的样式

（4）设定绘图样式

strokeStyle：图形边框的样式

（5）指定线宽

context.lineWidth = 150;

（6）指定颜色值

（7）绘制正方形

context.fillRect(50,50,500,500);
context.strokeRect(50,50,500,500);