图片真的变大缩小了

<script language="javascript">
    var oTime;
    function chgSize(args) {
        var oImg = document.all('oImg');
        oImg.style.zoom = parseInt(oImg.style.zoom) + (args ? +1 : -1)  + '%';
        oTime = window.setTimeout('chgSize(' + args + ')', 10);
    }   
document.onmouseup = function() {
window.clearTimeout(oTime);
} 
</script>
<div style="height: 200px; overflow: auto;">
<img id="oImg" src="a.jpg"   style="zoom: 100%;"/>
</div>
<input type=button onmousedown="chgSize(true);" onmouseup="window.clearTimeout(oTime);" Value=↑>
<input type=button onmousedown="chgSize(false);" onmouseup="window.clearTimeout(oTime);" Value=↓>

 

无限缩小后就死掉了,方法还在研究中