从网上摘的一个图片自适应大小的js代码 高手请飘过

function fImageAuto(nID,nMaxWidth,nMaxHeight)
{
var objParentID =document.getElementById(nID);
var objImg =objParentID.getElementsByTagName("img");
var nImgNewRate =0;
var nImgOldRate =nMaxWidth/nMaxHeight;
for (i=0;i=nImgOldRate) {
objImg[i].style.height =nMaxWidth/nImgNewRate +"px";
objImg[i].style.width =nMaxWidth +"px";
objImg[i].style.marginTop =Math.round((nMaxHeight-nMaxWidth/nImgNewRate)/2) +"px";
}else{
objImg[i].style.width =nMaxHeight*nImgNewRate +"px";
objImg[i].style.height =nMaxHeight +"px";
objImg[i].style.marginLeft =(nMaxWidth-nMaxHeight*nImgNewRate)/2 +"px";
}
}
}