这个效果并不难，要点是位置和比例设置，

捕获鼠标位置、判断鼠标位置区域、还有onmouseover事件、onmousemove事件、onmouseout事件

设置显示大图的比例，小图上显示的切图比例都要弄准确点，最好是2倍啦，4倍啦。

主要注意宽度，我这里的图片m.jpg是1440X900的....

复制代码 代码如下:

放大镜效果

*{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;}

var $=function(id){return typeof id=="string"?document.getElementById(id):id}

var smallimg = $("smallimg");

var showimg = $("showimg");//滤镜图片

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;

//上面两个变量指明showimg允许活动的区域

};

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;

//获取当前移动的showimg位置 计算方法是 鼠标坐标 - 最外面容器的坐标 - 盒子的宽(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"

};

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