var preloaded = [];
for (var i = 1; i <= 9; i++)
{
	preloaded[i] = [loadImage(i + "_on.gif"), loadImage(i + "_ov.gif")];
}

function init()
{
	if (mtDropDown.isSupported())
	{
		mtDropDown.initialize();

		menu1.onactivate = function() { swapImage("button1", preloaded[1][1].src) };
		menu1.ondeactivate = function() { swapImage("button1", preloaded[1][0].src) };

		menu2.onactivate = function() { swapImage("button2", preloaded[2][1].src) };
		menu2.ondeactivate = function() { swapImage("button2", preloaded[2][0].src) };

		menu3.onactivate = function() { swapImage("button3", preloaded[3][1].src) };
		menu3.ondeactivate = function() { swapImage("button3", preloaded[3][0].src) };

		menu4.onactivate = function() { swapImage("button4", preloaded[4][1].src) };
		menu4.ondeactivate = function() { swapImage("button4", preloaded[4][0].src) };

		menu5.onactivate = function() { swapImage("button5", preloaded[5][1].src) };
		menu5.ondeactivate = function() { swapImage("button5", preloaded[5][0].src) };

		menu6.onactivate = function() { swapImage("button6", preloaded[6][1].src) };
		menu6.ondeactivate = function() { swapImage("button6", preloaded[6][0].src) };

		menu7.onactivate = function() { swapImage("button7", preloaded[7][1].src) };
		menu7.ondeactivate = function() { swapImage("button7", preloaded[7][0].src) };

		menu8.onactivate = function() { swapImage("button8", preloaded[8][1].src) };
		menu8.ondeactivate = function() { swapImage("button8", preloaded[8][0].src) };

		menu9.onactivate = function() { swapImage("button9", preloaded[9][1].src) };
		menu9.ondeactivate = function() { swapImage("button9", preloaded[9][0].src) };

	}
}

function loadImage(sFilename)
{
	var img = new Image();
	img.src ="http://www.dicp.cas.cn/images/" + sFilename;
	return img;
}

function swapImage(imgName, sFilename)
{
	document.images[imgName].src = sFilename;
}