// JScript 文件
//取得页面尺寸
function getPageSize() {
		
		var docElem	= document.documentElement
        //可见区域宽度
		this.width	= self.innerWidth  || (docElem&&docElem.clientWidth)  || document.body.clientWidth;
		//可见区域高度
		this.height	= self.innerHeight || (docElem&&docElem.clientHeight) || document.body.clientHeight;
		//页面的总高度
		this.docheight = Math.max(document.documentElement.scrollHeight, document.documentElement.clientHeight);
}			
				
//取得对象尺寸
function getElementSize(elem) {
		this.width	= elem.clientWidth  || elem.style.pixelWidth;
		this.height = elem.clientHeight || elem.style.pixelHeight;
}				
				
//计算滚动条像素
function getScrollPos() {
		
		var docElem		= document.documentElement;

		this.scrollX	= self.pageXOffset || (docElem&&docElem.scrollLeft) || document.body.scrollLeft;

		this.scrollY	= self.pageYOffset || (docElem&&docElem.scrollTop)  || document.body.scrollTop;
}

//使对象居为MarginCenter
function posToMarginCenter(elem) {
		var scrollPos	= new getScrollPos();					
		var pageSize	= new getPageSize();		
		var emSize		= new getElementSize(elem);
		var pageSizeWidth = pageSize.width;
		var pageSizeheight = pageSize.height;
		//emSize.height/emSize.width
		var x			= Math.round(pageSizeWidth/2) - (emSize.width /2) + scrollPos.scrollX;
		var y			= Math.round(pageSizeheight/2) - (emSize.height /2) + scrollPos.scrollY; 		
		elem.style.marginLeft	= x+'px';
		elem.style.marginTop = y + 'px';
}

//使对象居为屏幕中央
function posToCenter1(elem) {
		var scrollPos	= new getScrollPos();					
		var pageSize	= new getPageSize();		
		var emSize		= new getElementSize(elem);
		var pageSizeWidth = pageSize.width;
		var pageSizeheight = pageSize.height;
		//emSize.height/emSize.width
		var x			= Math.round(pageSizeWidth/2) - (emSize.width /2) + scrollPos.scrollX;
		var y			= Math.round(pageSizeheight/2) - (emSize.height /2) + scrollPos.scrollY; 		
		elem.style.left	= x+'px';
		elem.style.top = y + 'px';
		elem.style.position = 'absolute';
}

//使对象居为屏幕中央
function posToCenter(elem, width, height ) {
		var scrollPos	= new getScrollPos();					
		var pageSize	= new getPageSize();		
		var pageSizeWidth = pageSize.width;
		var pageSizeheight = pageSize.height;
		//emSize.height/emSize.width
		var x			= Math.round(pageSizeWidth/2) - (width /2) + scrollPos.scrollX;
		var y			= Math.round(pageSizeheight/2) - (height /2) + scrollPos.scrollY; 		
		elem.style.left	= x+'px';
		elem.style.top = y + 'px';
		elem.style.position = 'absolute';
}