<STYLE type=text/css> /*pre css reset*/ body,th,td { font-size:12px;font-family:Tahoma,Helvetica,Arial,'\5b8b\4f53','\5FAE\8F6F\96C5\9ED1',sans-serif; } body,th,td,ol,ul,li,dl,dt,dd,h1,h2,h3,h4,h5,h6,pre,form,fieldset,legend,input,button,textarea,p { margin:0;padding:0; } fieldset,img { border:none; } a {color:#3366CC; text-decoration:none;outline:none;} a:hover {color:#FF6600;text-decoration:underline;} /************************************************************/ .test { } .test h3{ margin:10px auto;} .test dt {line-height:25px;margin-top:5px;} .cla {border:solid 1px #09c;} </STYLE> <H3>演示示例</H3> <DL> <DT>1.图片和放大使用不同的图片（大小图片要比例相同）也可以指定放大倍数（相对于小图片计算） <PRE>new imageZoom("img1",{ //mul:6,//指定放大的倍数 onShow:function() { document.title="show,you are moving on the image."; }, onHide:function() { document.title="you mouse move out the image"; }, bigImg:"../images/tong.jpg"//指定放大图片路径 }); </PRE> <DD><a href="javascript:;" onclick="showimg('/UploadFiles/2021-04-02/20091115231842561.jpg');"><img src="/UploadFiles/2021-04-02/20091115231842561.jpg" alt="javascript 图片放大效果函数" onmousewheel="return bbimg(this)" onload="javascript:resizepic(this)" border="0"/></a> <DT>2.使用同一图片给小图片设定宽或高，这里指定了:style="height:300px;" ，(偷懒模式，^o^,后面几个也是这样） <PRE>new imageZoom("dd2",{//第一个参数指定一个图片或者其id（也可以为图片的容器或者id,容器中第一个子元素要为图片） //mul:3 }); </PRE> <DD id=dd2><a href="javascript:;" onclick="showimg('/UploadFiles/2021-04-02/20091115231842599.jpg');"><img src="/UploadFiles/2021-04-02/20091115231842599.jpg" alt="javascript 图片放大效果函数" onmousewheel="return bbimg(this)" onload="javascript:resizepic(this)" border="0"/></a> <DD id=info> <DT>3.放大图片显示到指定的容器中 <PRE>new imageZoom("img3",{ viewer:"imgshow"//指定要显示的div或者其id }) </PRE> <DD><a href="javascript:;" onclick="showimg('/UploadFiles/2021-04-02/o_wanx.jpg');"><img src="/UploadFiles/2021-04-02/o_wanx.jpg" alt="javascript 图片放大效果函数" onmousewheel="return bbimg(this)" onload="javascript:resizepic(this)" border="0"/></a> <DD>图片预览： <DT>4.显示大图的div以指定倍数 <PRE>new imageZoom("img4",{ mul:5,//放大5倍 viewerCla:"cla",//指定显示层的样式 viewerMul:1.2//展示层以小图片的1.2倍大小 }); </PRE> <DD><a href="javascript:;" onclick="showimg('/UploadFiles/2021-04-02/20091115231842981.jpg');"><img src="/UploadFiles/2021-04-02/20091115231842981.jpg" alt="javascript 图片放大效果函数" onmousewheel="return bbimg(this)" onload="javascript:resizepic(this)" border="0"/></a> </DD></DL>点击下载js源码 PS:为了避免ff下的出问题（在ff下如果网页加载实在太慢，可能无法获取图片大小）最好将代码放在onload中执行update: 2009-11-15 21:40,感谢danica7773，按其建议加上 自定义显示层的样式，显示和隐藏的事件
[Ctrl+A 全选 注:引入外部Js需再刷新一下页面才能执行]
imageZoom.js
复制代码 代码如下:
/*
*Author:sohighthesky
*Date:2009-11-14
*/
/*
*img 指定要放大的图片或者其id
*options:参见代码中setOptions中的注释
*/
var imageZoom = function(img,options) {
    this.img=this.g(img);
    if(this.img.nodeName!="IMG") {
        if(this.img && this.img.children[0].nodeName=="IMG")this.img=this.img.children[0];
        else throw Error("Invalid argument [img] !");
    }
    this.setOptions(options);
    this.init();
}
imageZoom.prototype={
    g:function(id) {return typeof(id)=="string"?document.getElementById(id):id;},
    ae:function(el,type,call) {
if(el.addEventListener)el.addEventListener(type,call,false);
        else el.attachEvent("on"+type,call);
},
    getPos:function(o){//取元素坐标
        var x = 0, y = 0;
        do{x += o.offsetLeft; y += o.offsetTop;}
        while(o=o.offsetParent);
        return {'x':x,'y':y};
    },
    setOptions:function(options) {
     this.options={
     mul:0,//默认为不放大（显示图片的原来大小）
         bigImg:null,//指定放大的图片路径（要跟小图成比例才好）
         viewer:null, //指定显示的位置(可以为一个div或者其id)
         viewerCla:"",//预览的div的类样式
         viewerMul:1,//指定显示div的放大倍数，默认为原大小,设置viewer时此参数无效
         onShow:function(){},
         onHide:function(){}
     };
        for(var o in options) {this.options[o]=options[o];}
        this.options.bigImg =this.options.bigImg ||this.img.src;
},
getSize:function(o) {
        return {w:o.offsetWidth,h:o.offsetHeight};
},
    createView:function() {        
        var _is=this.getSize(this.img);
        var d=document;
        if(this.options.viewer){
            this.viewer=this.g(this.options.viewer);
            this.viewer.style.overflow="hidden";
            this.viewer.style.position="relative";
        } else {
            this.viewer=d.createElement("div");
            this.viewer.className=this.options.viewerCla;
            var pos=this.getPos(this.img);
            this.viewer.style.cssText="display:none;overflow:hidden;position:absolute;top:"+pos.y+"px;left:"+(pos.x+_is.w+10)+"px;height:"+_is.h*this.options.viewerMul+"px;width:"+_is.w*this.options.viewerMul+"px";
            d.body.appendChild(this.viewer);
        }        
        this.viewimg=d.createElement("img");
        this.viewimg.style.cssText="position:relative;left:-33%;top:-33%;";
        this.viewimg.src=this.options.bigImg;
        if(this.options.mul) {//设置放大倍数
            this.viewimg.style.width=_is.w*this.options.mul +"px";
            this.viewimg.style.height=_is.h*this.options.mul +"px";
        }
        this.viewer.appendChild(this.viewimg);
    },
    move:function(e) {
        if(!this.options.mul)
         this.options.mul=this.viewimg.offsetHeight/this.img.offsetHeight;
        var pos=this.getPos(this.img);
        var l=e.clientX-pos.x+(document.documentElement.scrollLeft || document.body.scrollLeft);//鼠标位置相对于图片左上角的偏移
        var t=e.clientY-pos.y+(document.documentElement.scrollTop || document.body.scrollTop);
        var zs=this.getSize(this.viewer);
        var pl=-l*this.options.mul+zs.w/2;
        var pt=-t*this.options.mul+zs.h/2;
        pl=pl>0?0:pl;
        pt=pt>0?0:pt;

var vs=this.getSize(this.viewimg);
pl=Math.max(pl,zs.w-vs.w);
pt=Math.max(pt,zs.h-vs.h);

        this.viewimg.style.left=pl+"px";
        this.viewimg.style.top=pt+"px";
    },
    init:function() {
     var o=this;
     var load=function(a) {//图片加载
     o.createView.call(o);
     o.img.setAttribute("alt","");
     o.ae(o.img,"mousemove",function(event){o.move.call(o,event);});
         if(!o.options.viewer) {
         o.ae(o.img,"mouseover",function(){o.options.onShow();o.viewer.style.display=""});
         o.ae(o.img,"mouseout",function(){o.options.onHide();o.viewer.style.display="none"});
         }
     };
     if(typeof(document.readyState)=="undefined" || window.opera) {
            var de=document.documentElement || document.body;
            var h=de.scrollHeight;
            var t=setInterval(function() {
                if(h==de.scrollHeight){
                    clearInterval(t);
                    load();                    
                } else h=de.scrollHeight;
            },500);
     } else if(document.readyState=="complete")
     load();
     else
     o.ae(window,"load",load);
    }
};