js改变img宽高

<img src="http://img2.itiexue.net/1228/12281366.jpg" border="0" onmousewheel="return bbimg(this)" onload="javascript:if(this.width>screen.width-500)this.width=screen.width-500" border="0" alt="从目前网络流传照片不负责浅析中国四代机的长度！(组图) " title="铁血网提醒您：点击可查看大图"/>

 

 

function bbimg(o)

{

var zoom=parseInt(o.style.zoom, 10)||100;

zoom+=event.wheelDelta/12;if (zoom>0) o.style.zoom=zoom+'%';

return false;

}