function moveImage (step) {
  var selected = document.getElementById ("IMAGE_SELECTED").getAttribute ("src");

  selected = basename (selected);

  for (var i in imagelist) {
    if (basename (imagelist [i]) == selected) {
      break;
    }
  }

  i = parseInt (i);

  i += step;
  if (i < 0) {
    i = imagelist.length-1;
  }
  else if (i > imagelist.length-1) {
    i = 0;
  }

  document.getElementById ("IMAGE_SELECTED").setAttribute ("src", imagelist [i]);
  document.getElementById ("IMAGE_LABEL").innerHTML = labellist [i];
}

function basename (url) {
  url = url.split ("/");
  return url [url.length-1];
}

function textVisible (anchor, bool) {
  var nodes = anchor.getElementsByTagName ("*");
  for (var i = 0 ; i < nodes.length ; ++i) {
    if (nodes.item (i).className == "label") {
      nodes.item (i).style.display = bool ? "block" : "none";
    }
    else if (nodes.item (i).tagName == "IMG") {
      nodes.item (i).style.display = bool ? "none" : "inline";
    }
  }
}