​x
 
<html>
<head>
<script type="text/javascript" src="/jquery/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
  $("button").click(function(){
    $("img").attr("width",function(n,v){
      return v-50;
    });
  });
});
</script>
</head>
<body>
<img src="/i/eg_smile.gif" width="128" height="128" />
<br />
<button>减少图像的宽度 50 像素</button>
</body>
</html>
​