JQuery控制图片由中心点逐渐放大效果

<meta charset="utf-8"> 
<style type="text/css"> 
#div1{ width:600px; height:400px; margin:50px auto; position:relative; text-align: center; padding-left:50px;} 
#div1 img{ position:absolute; left:0; top:0; margin: 0 auto;} 
</style> 
<div id="div1"> 
<img src="images/1.jpg" width="100px" height="80px"> 
</div> 
<script type="text/javascript" src="js/jquery-1.7.1.min.js"></script> 
<script type="text/javascript"> 
$(function(){ 
$('#div1 img').mouseenter(function(){ 
var wValue=1.5 * $(this).width(); 
var hValue=1.5 * $(this).height(); 
$(this).animate({width: wValue, 
height: hValue, 
left:("-"+(0.5 * $(this).width())/2), 
top:("-"+(0.5 * $(this).height())/2)}, 1000); 
}).mouseleave(function(){ 
$(this).animate({width: "100", 
height: "80", 
left:"0px", 
top:"0px"}, 1000 ); 
}); 
}); 
</script>