function setHeaderImage(a) {
  var thumb_src = a.getElementsByTagName('img')[0].src;
  var new_src = thumb_src.replace(/thumbnails\//g,'') 
  var img1 = (document.getElementById('header-image-1')).getElementsByTagName('img')[0];
  var img2 = (document.getElementById('header-image-2')).getElementsByTagName('img')[0];
  if(img1.src != new_src) {
    img2.src = img1.src;
    img1.src = new_src; 
  }

  return false;
}

var last_image_changed = 0;

function startSlideShow(galery_id,pictures_string) 
{
  var pictures = pictures_string.split(';'); 

  var galery = document.getElementById(galery_id);
  var image_tags = galery.getElementsByTagName('img')  
  if(pictures.length<4)
    return false;
  var new_picture = null;
  
  var j=0;
  while(new_picture==null && j<20) {
    new_picture = pictures[Math.round(Math.random()*(pictures.length-1))];
    
    for(var i=0;i<image_tags.length;i++) { //kontrola zda uz neni zobrazen
      if(image_tags[i].src==new_picture) new_picture=null;  
    }
    j++;
  }
  
  if(new_picture == null)
   new_picture = pictures[Math.round(Math.random()*(pictures.length-1))];
  
  j=0; 
  var new_image_tag = null;
  while(new_image_tag==null && j<20) {
    new_image_tag = Math.round(Math.random()*(image_tags.length-1));    
    if(last_image_changed==new_image_tag) new_image_tag=null;
    j++;
  }
  
  if(new_image_tag==null ) new_image_tag = Math.round(Math.random()*(image_tags.length-1)); 
  
  last_image_changed = new_image_tag;
  
  jQuery('#'+image_tags[new_image_tag].id).fadeOut('slow',function() {image_tags[new_image_tag].src=new_picture;});  
  jQuery('#'+image_tags[new_image_tag].id).fadeIn('slow');
  setTimeout("startSlideShow('"+galery_id+"','"+pictures_string+"')",3000);
  return false; 
}