//首先输出一个层用于存放大图
document.write("<div id='div_bigImg' style='overflow:hidden;position:absolute;border:solid double #999999 2px;'></div>");
var iDivHeight = 300; //放大显示区域宽度
var iDivWidth = 400;//放大显示区域高度
var iMultiple = 1; //放大倍数
//显示放大图，鼠标移动事件和鼠标点击事件都会调用本事件
//原理：依据鼠标对应缩略图左上角（0，0）上的位置控制放大图左上角对应显示区域左上角（0，0）的位置
function showBigPic(src)
{
	//判断鼠标事件产生时是否同时按下了
	if ((event.button == 1) && (event.ctrlKey == true))
		iMultiple -= 1;
	else
		if (event.button == 1)
		   iMultiple += 1;
		if (iMultiple < 2) 
		   iMultiple = 2;
		if (iMultiple > 14)
		   iMultiple = 14;
	   
	var iPosX, iPosY; //放大图对应显示区域左上角的坐标
	var iMouseX = event.offsetX; //鼠标对应缩略图左上角的横坐标
	var iMouseY = event.offsetY; //鼠标对应缩略图左上角的纵坐标
	var iBigImgWidth = src.clientWidth * iMultiple; //放大图宽度，是缩略图的宽度乘以放大倍数
	var iBigImgHeight = src.clientHeight * iMultiple; //放大图高度，是缩略图的高度乘以放大倍数
	
	if (iBigImgWidth <= iDivWidth)
	{
		iPosX = (iDivWidth - iBigImgWidth) / 2;
	}
	else
	{
		if ((iMouseX * iMultiple) <= (iDivWidth / 2))
		{
		   iPosX = 0;
		}
		else
		{
		   if (((src.clientWidth - iMouseX) * iMultiple) <= (iDivWidth / 2))
		   {
			iPosX = -(iBigImgWidth - iDivWidth);
		   }
		   else
		   {
			iPosX = -(iMouseX * iMultiple - iDivWidth / 2);
		   }
		}
	}
	
	if (iBigImgHeight <= iDivHeight)
	{
		iPosY = (iDivHeight - iBigImgHeight) / 2;
	}
	else
	{
		if ((iMouseY * iMultiple) <= (iDivHeight / 2))
		{
		   iPosY = 0;
		}
		else
		{
		   if (((src.clientHeight - iMouseY) * iMultiple) <= (iDivHeight / 2))
		   {
			iPosY = -(iBigImgHeight - iDivHeight);
		   }
		   else
		   {
			iPosY = -(iMouseY * iMultiple - iDivHeight / 2);
		   }
		}
	}
	div_bigImg.style.display="";
	//设置DIV坐标以及宽高
	if(document.body.scrollTop>0)
	{
		div_bigImg.style.top = document.body.scrollTop + event.screenY - (screen.height - document.body.offsetHeight) / 2;
	}
	else
	{
	    div_bigImg.style.top = event.screenY - (screen.height - document.body.offsetHeight) / 2;
	}
	
	if(screen.width-(event.screenX+40)<iDivWidth)
	{
	   div_bigImg.style.left = event.screenX - (iDivWidth+20);
	}
	else
	{ 
	   div_bigImg.style.left = event.screenX+20;
	}

	div_bigImg.style.height = iDivHeight;
	div_bigImg.style.width = iDivWidth;
	
	if (div_bigImg.innerHTML == "")
	{
		div_bigImg.innerHTML = "<img id=BigImg style='position:relative'>";
		BigImg.src = src.src;
	}
	BigImg.width = iBigImgWidth;
	BigImg.height = iBigImgHeight;
	BigImg.style.top = iPosY;
	BigImg.style.left = iPosX;
	/*
	//设置背景与图层的透明度
  	src.style.filter='alpha(opacity=100)';
	div_bigImg.style.filter='alpha(opacity=100)';
	*/
}
function closeBigPic()
{
   try
   {
      div_bigImg.style.display="none";
   }
   catch(error){}
   /*
   //取消透明度
   var objTagName = document.getElementsByTagName("img");
   for(var i=0;i<objTagName.length;i++)
   {
	    objTagName[i].style.filter='alpha(opacity=100)';
   }
   */
}