HTML canvas原生js实现鼠标画图

效果展示：

查看效果可点击下载源文件 http://i.cnblogs.com/Files.aspx

html完整代码：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>canvas鼠标画图</title>
<style>
	body { background-color:yellow;}
	#c1 { background-color: white; }
</style>
<script>
window.onload = function() {
　　var oC = document.getElementById('c1');
　　var oCG = oC.getContext('2d');
　　oC.onmousedown = function(ev) {
	var ev = ev || window.event;
	oCG.moveTo(ev.clientX-oC.offsetLeft,ev.clientY-oC.offsetTop); //ev.clientX-oC.offsetLeft,ev.clientY-oC.offsetTop鼠标在当前画布上X,Y坐标
	document.onmousemove = function(ev) {
		var ev = ev || window.event;//获取event对象
		oCG.lineTo(ev.clientX-oC.offsetLeft,ev.clientY-oC.offsetTop); 
		oCG.stroke();
		};
	oC.onmouseup = function() {
		document.onmousemove = null;
		document.onmouseup = null;
		};
　　　　};
};
</script>
</head>

<body>
	<canvas id="c1" width="400px" height="400px"> <!--宽高写在html里，写在css里有问题-->
    	<span>该浏览器不支持canvas内容</span> <!--对于不支持canvas的浏览器显示-->
    </canvas>
</body>
</html>

年级1