// JavaScript Document
function $ (obj)
{
	return document.getElementById (obj);
};
//图片自动缩放，垂直居中
function picCheck (obj, maxWidth, maxHeight)
{
	obj.style.width = "auto";
	if (obj.width > maxWidth)
	{
		obj.style.width = maxWidth + 'px';
	}
	if (obj.height > maxHeight)
	{
		obj.style.width = (obj.width * maxHeight / obj.height + 1) + 'px';
	}
	parentHeight = obj.parentNode.clientHeight == 0?obj.parentNode.parentNode.clientHeight : obj.parentNode.clientHeight;
	obj.style.marginTop = (parentHeight - obj.clientHeight) / 2 + 'px';
}
function picPosition (obj)
{
	parentHeight = obj.parentNode.clientHeight == 0?obj.parentNode.parentNode.clientHeight : obj.parentNode.clientHeight;
	obj.style.marginTop = (parentHeight - obj.clientHeight) / 2 + 'px';
}