function getfgbanner() {
	var bsrc = document.getElementById('banner_img').src;
	var spsrc = bsrc.split("/");
	return spsrc[spsrc.length - 1];
}

function getbgbanner() {
	var bsrc = document.getElementById('banner_div').style.backgroundImage;
	var spsrc = bsrc.split("/");
	return spsrc[spsrc.length - 1].substring(0, spsrc[spsrc.length - 1].length - 1);
}

function getindex(arr, val) {
	for(var i = 0; i < arr.length; i++) {
		if(arr[i] == val)
			return i;
	}
}

function swapBanner() {
	var speed = Math.round(750 / 100);
	var timer = 0;

	for(var i = 100; i >= 0; i--) {
		setTimeout("changeOpac_banner('banner_img', " + i + ")", (timer * speed));
		timer++;
	}
}

function changeOpac_banner(id, opac) {
	var object = document.getElementById(id).style;
	object.opacity = (opac / 100);
	object.filter = "alpha(opacity=" + opac + ")";

	if(opac == 0) {
		var nextI = getindex(banners, getbgbanner());
		var onextI = 0;
		document.getElementById('banner_img').src = 'http://sfg-singen.de/template_markus/banners/'+getbgbanner();

		object.opacity = (100 / 100);
		object.filter = "alpha(opacity=" + 100 + ")";

		//get next IMG
		if((nextI + 1) < banners.length)
			onextI = nextI + 1;

		document.getElementById('banner_div').style.backgroundImage = 'url(http://sfg-singen.de/template_markus/banners/'+banners[onextI]+')';
	}
}

window.onload = function() { window.setInterval("swapBanner()", 15000); };