var idlNumImages      = 37;
var idlMaxImages      = 5;
var minAnimationDelay = 1000;
var maxAnimationDelay = 5000;
var delayDelta        = 250;
var animationDelay    = minAnimationDelay;

function newImageArray(n) {
  var img = new Array(n);
  for(var i = 0; i < n; ++i) {
    img[i] = new Image();
  }
  return img;
}

function nextInt(max) {
  return Math.floor(max*Math.random());
}

function idlNextImage() {
  var index = nextInt(idlImages.length);
  document.images['idl'].src = idlImages[index].src;

  if(animationDelay < maxAnimationDelay)
    animationDelay+=delayDelta;

  setTimeout('idlNextImage()', animationDelay);
}

function loadImages(images, dir) {
  var file;

  for(var i = 0; i < images.length; ++i) {
    file = "";
    if(i < 10)
      file+="0";
    file+=i;
    file+=".jpg";
    images[i].src = dir + file;
  }
}

function loadRandomImages(images, dir, max) {
  var file;
  var num;

  for(var i = 0; i < images.length; ++i) {
    file = "";
    num  = nextInt(max);
    if(num < 10)
      file+="0";
    file+=num;
    file+=".jpg";
    images[i].src = dir + file;
  }
}

function init() {
  if(document.images) {
    /*
    idlImages = newImageArray(idlNumImages);
    loadImages(idlImages, "/images/idl/");
    */
    idlImages = newImageArray(idlMaxImages);
    loadRandomImages(idlImages, "/images/idl/", idlNumImages);
    setTimeout('idlNextImage()', maxAnimationDelay);
  }
}