window.onload = function() {
  katalog();
}

function katalog() {
  var imgs = getElementsByClass('prodimg', ge('hPimg'), 'div');
  
  for(var i=0;i<imgs.length;i++) {
    imgs[i].style.position = 'relative';
    var top = ((imgs[i].parentNode.offsetHeight - imgs[i].offsetHeight) / 2);
    
    imgs[i].style.top = top + 'px';
  }
}