var randomImage = -1;
var imageArray = new Array();
var locationArray = new Array();

imageNumber = 0;

imageArray[imageNumber] = "uni-ulm.gif";locationArray[imageNumber++] = "http://www.uni-ulm.de";
imageArray[imageNumber] = "mwkbwl.gif";locationArray[imageNumber++] = "http://www.mwk.baden-wuerttemberg.de";
imageArray[imageNumber] = "scultetus.gif";locationArray[imageNumber++] = "http://www.scultetus-gesellschaft.de";



var imagePath = "images/werbung/";
	
var upperbound = imageArray.length-1;
var lowerbound = 0;


//alle bilder werden vorgeladen
for(var i=0; i<imageArray.length; i++){
	preload("image" + i,imagePath + imageArray[i]);
}


function getStartImage(){
randomnumber = wuerfeln();
document.getElementById("sponsoren").src = imagePath + imageArray[randomnumber];
document.getElementById("sponsorenlink").href = locationArray[randomnumber];
}

function startImageShow(rnumber){
	randomnumber = wuerfeln();
	/*
	verhindere zweimalige anzeige
	*/
	while(rnumber == randomnumber){
		randomnumber = wuerfeln();
	}
	document.getElementById("sponsoren").src = imagePath + imageArray[randomnumber];
	document.getElementById("sponsorenlink").href = locationArray[randomnumber];
	setTimeout("startImageShow("+randomnumber+")",4000);
}

//eine zufallszahl wird ermittelt
function wuerfeln(){
	return parseInt((upperbound - lowerbound + 1) * Math.random() + lowerbound);
}

function preload(imgObj,imgSrc) {
	if (document.images) {
		eval(imgObj+' = new Image()')
    	eval(imgObj+'.src = "'+imgSrc+'"')
  	}
}