<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>canvas实现简单的画图工具中画笔效果</title>
</head>
<body>
<canvas width="500" height="500" style="background:#eee;"></canvas>
<script>
var canvas = document.getElementsByTagName(‘canvas‘)[0];
var con = canvas.getContext(‘2d‘);
canvas.onmousedown = function(e){
var mx = e.layerX,
my = e.layerY;
con.moveTo(mx,my);
canvas.onmousemove = function(e){
var ex = e.layerX,
ey = e.layerY;
con.lineTo(ex,ey);
con.stroke();
}
canvas.onmouseup = function(){
canvas.onmousemove = null;
canvas.onmouseup = null;
}
}
</script>
</body>
</html>
原文：http://www.cnblogs.com/webBlog-gqs/p/7956004.html