js图片放大镜特效代码

 <script language="JavaScript">
 <!--
 var srcX = 1024; //原图长宽
 var srcY = 768;
 var bigX = 500; //原比例预览大小,可以设置成任意大小
 var bigY = 300;
 var smallX = 256; //缩略图大小,要与原大小成比例
 var smallY = 192;
 var viewX = bigX / srcX * smallX; //预览范围
 var viewY = bigY / srcY * smallY;
 var bl = srcX / smallX;//缩小比例
 var border = 8; //边框
 window.onload=function (){
     bigbox.style.borderWidth=border;
     bigbox.style.width=bigX+border*2;
     bigbox.style.height=bigY+border*2;
     smallpic.width=smallX;
     smallpic.height=smallY;
     view.style.width=viewX;
     view.style.height=viewY;
     smallbox.style.borderWidth=border;
     if (window.event){
         smallbox.style.width=smallpic.offsetWidth+border*2;
         smallbox.style.height=smallpic.offsetHeight+border*2;
     }else{
         smallbox.style.width=smallpic.offsetWidth;
         smallbox.style.height=smallpic.offsetHeight;
     }
     move(event);
 }
 function move(e){
     var e = window.event?window.event:e;
     var iebug = 0;
     if (window.event){
         var vX = e.offsetX - viewX/2;
         var vY = e.offsetY - viewY/2;
     }else{
         var vX = e.pageX - viewX/2 - smallbox.offsetLeft - border;
         var vY = e.pageY - viewY/2 - smallbox.offsetTop - border;
         iebug = 2;
     }
     if (vX < 0) vX = 0;
     if (vY < 0) vY = 0;
     if (vX > smallX - viewX - iebug) vX = smallX - viewX - iebug;
     if (vY > smallY - viewY - iebug) vY = smallY - viewY - iebug;
     view.style.left = vX + smallbox.offsetLeft + border;
     view.style.top = vY + smallbox.offsetTop + border;
     bigbox.style.backgroundPosition= - vX * bl + " " + -vY * bl;
 }
 //-->
 </script>

 <style type="text/css">
 <!--
 *{padding:0;margin:0}
 img{display:block;}
 #smallbox{border:1px #c33 solid;float:left;width:0;height:0;overflow:hidden}
 #bigbox{border:1px #c33 solid;width:0px;height:0px;float:left;background:url('/upload/20071130224657571.jpg') no-repeat;}
 #view{border:1px #ddd solid;width:0px;height:0px;position:absolute}
 .head{text-align:center;line-height:40px;font:bold 16px/40px;color:red}
 //-->
 </style>
 <div class="head">图片放大效果</div>
 <div id="smallbox"><img id="smallpic" src="/upload/20071130224657571.jpg" border="0" onmousemove="move(event)"></div>
 <div id="bigbox"></div>
 <div id="view"></div>

代码最终的效果如下图：