function img_roll(imgObject)
{
	var ext = imgObject.src.substring(imgObject.src.lastIndexOf('.'));
	var splitted = imgObject.src.split(ext);
	prefix = splitted[0];
//	alert(prefix);
//	alert(prefix + "." + suffix);
	var newimg = prefix + "-on" + ext;
	imgObject.src = newimg;
	return true;
}

function img_unroll(imgObject)
{
	var ext = imgObject.src.substring(imgObject.src.lastIndexOf('.'));
	var splitted = imgObject.src.split("-on"+ext);
	prefix = splitted[0];

	var newimg = prefix + ext;
	imgObject.src = newimg;
	return true;
}