jQuery滚动加载图片效果的实现

<BR>/****************滚动加载图片函数****************/
     function scrollLoading(){
         var st = $(window).scrollTop(), sth = st + $(window).height();
         var $targetpics = $("img.scrloadpic");
         var len = $targetpics.length;
         for(var i=0; i< len; i++)
         {
             var $temppic = $targetpics.eq(i);
             var post = $temppic.position().top;
             var posb = post + $temppic.height();

             if((post > st && post < sth) || (posb > st && posb < sth))
             {

                 var url = $temppic.attr("xsrc");
                 if(url != "")
                 {
                    $temppic.attr("src", url);
                    $temppic.attr("xsrc", "");
                 }
             }
         }
     }

<img src="load.gif" xsrc="myimgae.jpg" class="scrloadpic"/>

scrollLoading();
$(window).bind("scroll", scrollLoading);