function initImgRotation() {
  // create rotating image objects here 
  // arguments: image name, rotation speed
  var rotator1 = new rotateImgObj('img1',400);
  // add the images to rotate into that image object  
  rotator1.addImages("01.jpg","02.jpg","03.jpg","04.jpg","05.jpg","06.jpg","07.jpg","08.jpg","09.jpg","10.jpg","11.jpg","12.jpg","13.jpg","14.jpg","15.jpg","16.jpg","17.jpg","18.jpg","19.jpg","20.jpg");
  rotator1.rotate();
  
  rotateImgObj.start();
}

// no need to edit code below 
/////////////////////////////////////////////////////////////////////
rotateImgObjs = []; // holds all rotating image objects defined
// constructor 

function rotateImgObj(nm,s) {
  this.speed=s; this.ctr=0; this.timer=0;  
  this.imgObj = document.images[nm]; // get reference to the image object
  base_url = this.imgObj.src;
  base_url = base_url.replace(/\/tb_[0-9][0-9]\.jpg$/,"/tb_");
  this.index = rotateImgObjs.length; rotateImgObjs[this.index] = this;
  this.animString = "rotateImgObjs[" + this.index + "]";
}

rotateImgObj.prototype = {
  addImages: function() { // preloads images
    this.imgObj.imgs = [];
    for (var i=0; arguments[i]; i++) {
      this.imgObj.imgs[i] = new Image();
      this.imgObj.imgs[i].src = base_url + arguments[i];
    }
  },

  rotate: function() {
    if (this.ctr < this.imgObj.imgs.length-1) this.ctr++;
    else this.ctr = 0;
    this.imgObj.src = this.imgObj.imgs[this.ctr].src;
  }
}

// sets up rotation for all defined rotateImgObjs
rotateImgObj.start = function() {
  for (var i=0; i<rotateImgObjs.length; i++) 
    rotateImgObjs[i].timer = setInterval(rotateImgObjs[i].animString + ".rotate()", rotateImgObjs[i].speed);                     
}