如何获得指定层中所有的图像高宽？？

Question

<div style="position: absolute; width: 142px; height: 556px; z-index: 1; left: 484px; top: 27px" id="layer1">
<img border="0" src="file:///C:/Documents%20and%20Settings/Administrator/桌面/新建%20BMP%20图像.bmp">
<img border="0" src="file:///C:/Documents%20and%20Settings/Administrator/桌面/新建%20BMP%20图像.bmp" >

</div>
<script>
var imgs =  layer1.getElementsByTagName("IMG");
for(var i = 0 ; i < imgs.length;i++)
{
document.write(imgs[i].offsetWidth+"|"+ imgs[i].offsetHeight+"<br>");
}
</script>