假缩略图

<script language="javascript">
function resize()
{
 var h = eval('star').height;
 var w = eval('star').width;
 if(h>300 || w>200)
 {
  if(h/w>2/3)
  {
   eval('star').height = 300;
  }
  else
  {
   eval('star').width = 200;
  }
 }
}
</script>
<input type="file" onchange="eval('star').src=value;"><img id="star" onload="resize();">