function SlideShow(image_arr)  { //arr is the array of images in the slide show

    this.arr = image_arr;
    this.arrLength = this.arr.length;
    this.imagesLoaded = new Array(this.arrLength);
    this.imagesLoaded[0] = true; // this image is loaded by default
    this.imagesLoaded[1] = true; // this image is pre-loaded in the BODY tag

    for (i = 2; i < this.arrLength; i++) {
      this.imagesLoaded[i] = false;
    }

    this.indx = 0;
    this.direction = 0;

    this.arrLength -= 1;

    this.next = next;
    this.prev = prev;
    this.moveIndex = moveIndex;
    this.getNewIndexPosition = getNewIndexPosition;
    this.showImage = showImage;
  }


  function next() {
    this.moveIndex(1);
    this.showImage();
  }


  function prev() {
    this.moveIndex(-1);
    this.showImage();
  }


  function moveIndex(i) {

    this.indx = this.getNewIndexPosition(i);

  }

  function getNewIndexPosition(p) {

    var p_new = this.indx + p;

    if (p_new > this.arrLength) {
      p_new = 0;
    }
    else if (p_new < 0) {
      p_new = this.arrLength;
    }

    return p_new;

  }

  function showImage() {

    if (this.arr[this.indx] != null) {

      document.images.showcaseimage.src = this.arr[this.indx];

      if (! this.imagesLoaded[this.indx]) {
        this.imagesLoaded[this.indx] = true;
      }

      var prev = this.getNewIndexPosition(this.indx - 1);

      if (! this.imagesLoaded[prev]) {
        this.imagesLoaded[prev] = true;
        //alert("preloading " + this.arr[prev] + " indx="+ indx);
        MM_preloadImages(this.arr[prev]);
      }

      var next = this.getNewIndexPosition(this.indx + 1);

      if (! this.imagesLoaded[next]) {
        this.imagesLoaded[next] = true;
        //alert("preloading " + this.arr[next] + " indx="+ indx);
        MM_preloadImages(this.arr[next]);
      }
    }
  }