function shiftslide(slide, current, next) {
   var thisimage = 'slides-' + slide + '-' + current;
   var nextimage = 'slides-' + slide + '-' + next;
   document.getElementById('' + thisimage).style.visibility='hidden';
   document.getElementById('' + nextimage).style.visibility='visible';
}

var slides = new Array();
var imagecounts = new Array();
var indexes = new Array();

function registerSlide()
{
  var title = registerSlide.arguments[0];
  var imagecount = registerSlide.arguments.length - 1;

  if (!slides[title])
  {
    imagecounts[title] = imagecount;
    slides[title] = new Array(imagecount);
    indexes[title] = 0;

    for (var i = 0; i < imagecount; i++)
    {
      slides[title][i] = new Image();
      slides[title][i].src = registerSlide.arguments[i+1][0];
      slides[title][i].title = registerSlide.arguments[i+1][1];
    }
  }
}

function switchImage(slide, relativeIndex) {
    var index = (imagecounts[slide] + indexes[slide] + relativeIndex) % imagecounts[slide];
    indexes[slide] = index;
    document.images[slide].src = slides[slide][index].src;
    document.getElementById(slide + "-text").firstChild.data = slides[slide][index].title;
}

function nextImage(slide) { switchImage(slide, 1); }
function previousImage(slide) { switchImage(slide, -1); }