javascript 图片放大效果函数

/*
*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);
    }
};