這個效果並不難，重點是位置和比例設置，
捕捉滑鼠位置、判斷滑鼠位置區域、還有onmouseover事件、onmousemove事件、onmouseout事件
設定顯示大圖的比例，小圖上顯示的切圖比例都要弄準確點，最好是2倍啦，4倍啦。
主要注意寬度，我這裡的圖片m.jpg是1440X900的....
複製代碼代碼如下:
<!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>放大鏡效果</title>
<style type="text/css">
*{margin:0;padding:0;}
#smallimg{width:360px;float:left;position:relative;border:1px solid red;}
#smallimg img{width:360px;}
#bigimg{float:left;width:400px;height:400px;margin-left:40px;border:1px solid #ccc;display:none;}
#showimg{width:100px;height:100px;background:#fff;cursor:move;position:absolute;border:1px solid #666;opacity:0.5;filter:alpha(opacity=50);display:none;
</style>
</head>
<body>
<div id="smallimg">
<img src="jq/m.jpg"/>
<div id="showimg"></div>
</div>
<div id="bigimg"></div>
<script type="text/javascript">
var $=function(id){return typeof id=="string"?document.getElementById(id):id}
var smallimg = $("smallimg");
var showimg = $("showimg");//濾鏡圖片
var bigimg = $("bigimg");
var small_url = smallimg.getElementsByTagName("img")[0].getAttribute("src");
var show_half = maxWidth = maxHeight = 0;
smallimg.onmouseover = function(){
showimg.style.display = "block";
bigimg.style.display = "inline";
show_half = showimg.offsetHeight/2;
maxWidth = smallimg.clientWidth - showimg.offsetWidth;
maxHeight = smallimg.clientHeight - showimg.offsetHeight;
//上面兩個變數指明showimg允許活動的區域
};
smallimg.onmousemove = function(e){
var e=window.event?window.event:e;
var num=bigimg.clientWidth/showimg.clientWidth;
var Top = e.clientY - smallimg.offsetTop - show_half;
var Left = e.clientX - smallimg.offsetLeft - show_half;
//取得目前移動的showimg位置計算方法是滑鼠座標- 最外面容器的座標- 盒子的寬(高)的/2
Top = Top<0?0:Top>maxHeight?maxHeight:Top;
Left = Left<0?0:Left>maxWidth?maxWidth:Left;
showimg.style.top = Top + "px";
showimg.style.left = Left + "px";
bigimg.style.background = "url("+small_url+") -"+Left*num+"px -"+Top*num+"px no-repeat";
};
smallimg.onmouseout = function(){
showimg.style.display="none";
bigimg.style.background ="";
bigimg.style.display="none"
};
</script>
</body>
</html>