今天在玩 google earth 4.0b，发现 Print Screen 下来的图片很大，如果直接放在网页上，因为尺寸太大又不合适，又不想压缩图片的尺寸，于是乎就想到了这种方法，没想到实现起来比预想的要容易。这段代码还兼容 firefox。
限定滚动的范围，不会出现背景。
用到onmousemove事件，图片实时随鼠标移动而移动。
运行代码框
<!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=gb2312" />
<title>无标题文档</title>
<style type="text/css">
<!--
#pic {
width:420px;
height:300px;
border: 3px solid #ccc;
background-image: url(http://www.blueidea.com/articleimg/2006/06/3687/01.jpg);
background-repeat: no-repeat;
background-position: 0px 0px;
cursor: move;
}
-->
</style>
<script type="text/javascript">
<!--
var p = new Array();
var speed = 0.05; //速度
var picWidth = 1280; // 大图的宽高
var picHeight = 971;
var x,y // 鼠标点下去时背景的坐标
var x_new,y_new //位移
var haveclick = false;
function getmouseposition(event)
{
if(document.all)
{
x = document.body.scrollLeft+event.clientX;
y = document.body.scrollTop+event.clientY;
}else
{
x = event.layerX;
y = event.layerY;
}
haveclick = true;
}
function movestop()
{
haveclick = false;
}
function movestart(event)
{
if(haveclick)
{
if(document.getElementById('pic').style.backgroundPosition.length==0)
{document.getElementById('pic').style.backgroundPosition="0px 0px";}
p = document.getElementById('pic').style.backgroundPosition.split(" ")
if(document.all)
{
x_new = document.body.scrollLeft+event.clientX;
y_new = document.body.scrollTop+event.clientY;
}else
{
x_new = event.layerX;
y_new = event.layerY;
}
x2 = (speed*(x_new-x)+parseInt(p[0])).toString(10); // 计算位移量
y2 = (speed*(y_new-y)+parseInt(p[1])).toString(10);
if (x2<-picWidth+420) x2=-picWidth+420;
if (y2>0) y2=0;
if (x2>0) x2=0;
if (y2<-picHeight+300) y2=-picHeight+300;
document.getElementById('pic').style.backgroundPosition=x2+"px "+y2+"px";
}
}
-->
</script>
</head>
<body>
<div id="pic" onmousedown="getmouseposition(event)" onmousemove="movestart(event)" onmouseup="movestop()" onmouseout="movestop()"> </div>
</body>
</html>
[Ctrl+A 全部选择 提示：你可先修改部分代码，再按运行]