<!DOCTYPE HTML>
<html>
<head>
<script type="text/javascript">
var prex,prey;
var flag=0;
function start(t,e)
{
t.style.cursor="crosshair";
prex=e.clientX;
prey=e.clientY;
flag=1;
}
function stop()
{
flag=0;
}
function draw(t,e)
{
t.style.cursor="crosshair";
document.getElementById("x").innerHTML=e.clientX;
document.getElementById("y").innerHTML=e.clientY;
if (flag==1)
{
var c=document.getElementById("myCan").getContext("2d");
c.moveTo(prex,prey);
c.lineTo(e.clientX,e.clientY);
c.stroke();
prex=e.clientX;
prey=e.clientY;
}
}
function getOut()
{
flag=0;
}
</script>
</head>
<body>
<canvas id="myCan"
style="border:1px solid #000000" width="256" height="256"
onmousemove="draw(this,event)"
onmouseout="getOut()"
onmousedown="start(this,event)"
onmouseup="stop()">
</canvas>
<p id="x"></p>
<p id="y"></p>
</body>
</html>
原文：http://www.cnblogs.com/tiandsp/p/7467815.html