function createRequestObject() {

  var req;
  
  if(window.XMLHttpRequest) {
    // Firefox, Safari, Opera
    req = new XMLHttpRequest();
  } else if(window.ActiveXObject) {
    // IE 5+
    req = new ActiveXObject("Microsoft.XMLHTTP");
  } else {
    //Error for an old browser
    alert('Darstellen der Seite nicht möglich! Bitte aktualisieren Sie Ihren Browser!');
  }
  return req;
}

// XMLHttpRequest Object erstellen
var http = createRequestObject();

function sendReq(cat,bild)
{
    http.open('GET','/scripts/popup/popup.php?cat='+cat+'&bild='+bild,true);
    http.onreadystatechange = handleResponse;
    http.send(null);
}

function handleResponse()
{
  if(http.readyState == 4 && http.status == 200) {
    var response = http.responseText;
    if(response) {
      var responseArray = new Array();
      responseArray = response.split('|');
      switch(responseArray[0]) {
        case "bild":
          document.getElementById("bilddiv").style.width = responseArray[1]+'px';
          document.getElementById("bilddiv").style.height = responseArray[2]+'px';
          document.getElementById("bilddiv").style.backgroundImage = "url(\""+responseArray[3]+"\")";
    	    document.getElementById("bilddiv").style.display = "block";
          break;
        case "info":
          document.getElementById("bilddiv").innerHTML = responseArray[1];
          document.getElementById("bilddiv").style.display = "block";
          break;
      }
      posZentrieren();
    }
  }
}

function verstecke_layer()
{
  document.getElementById("bilddiv").innerHTML = '<a onclick="verstecke_layer();" href="#">X</a>';
  document.getElementById("bilddiv").style.backgroundImage = "none";
	document.getElementById("bilddiv").style.display = "none";
}

function posZentrieren()
{
  with(document.getElementById("bilddiv")) {      
    style.top = "100px";
    style.left = (offsetParent.offsetWidth - offsetWidth)/2 +"px";

//    style.top = (offsetParent.offsetHeight - offsetHeight)/2 +"px";
//    style.left = (offsetParent.offsetWidth - offsetWidth)/2 +"px";
  }
}