var bImagesLoaded = false;

function ImagePreloader(images, callback) {
    // store the call-back
    this.callback = callback;

    // initialize internal state.
    this.nLoaded = 0;
    this.nProcessed = 0;
    this.aImages = new Array();

    // record the number of images.
    this.nImages = images.length;

    // for each image, call preload()
    for (var i = 0; i < images.length; i++) {
      this.preload(images[i]);
    }
}

ImagePreloader.prototype.preload = function(image) {
   // create new Image object and add to array
   var oImage = new Image();
   
   this.aImages.push(oImage);
   

   // set up event handlers for the Image object
   oImage.onload = ImagePreloader.prototype.onload;
   oImage.onerror = ImagePreloader.prototype.onerror;
   oImage.onabort = ImagePreloader.prototype.onabort;

   // assign pointer back to this.
   oImage.oImagePreloader = this;
   oImage.bLoaded = false;

   // assign the .src property of the Image object
   oImage.src = image;
}

ImagePreloader.prototype.onComplete = function() {
   this.nProcessed++;

   if (this.nProcessed == this.nImages) {
      this.callback(this.aImages, this.nLoaded);
   }
}

ImagePreloader.prototype.onload = function() {
   this.bLoaded = true;
   this.oImagePreloader.nLoaded++;
   this.oImagePreloader.onComplete();
}

ImagePreloader.prototype.onerror = function() {
   this.bError = true;
   this.oImagePreloader.onComplete();
}

ImagePreloader.prototype.onabort = function() {
   this.bAbort = true;
   this.oImagePreloader.onComplete();
}

function onPreload(aImages, nImages) {
   if (nImages != aImages.length) {
      alert("images did not load");

      return;
   } else {
    bImagesLoaded = true;
   }
}

var imageArray = new Array();
imageArray.push("gfx/maintitleSmall.jpg");
imageArray.push("gfx/icoResponseCorrect2.gif");
imageArray.push("gfx/icoResponseIncorrect2.gif");
imageArray.push("gfx/btnExpandSmall.gif");
imageArray.push("gfx/btnEditSmall.gif");
imageArray.push("gfx/icoMultipleSelection.gif");
imageArray.push("gfx/objProgressBarIndicator.gif");
imageArray.push("gfx/censusButtons/repeat_off.jpg");
imageArray.push("gfx/censusButtons/pause_off.jpg");
imageArray.push("gfx/censusButtons/back_off.jpg");
imageArray.push("gfx/censusButtons/back_off.jpg");
imageArray.push("gfx/censusButtons/resources_off.jpg");
imageArray.push("gfx/censusButtons/fwd_off.jpg");
imageArray.push("gfx/edetailBackgroundHeader.gif");
imageArray.push("gfx/edetailBackgroundFill.gif");
imageArray.push("gfx/edetailBackgroundFooter.gif");
imageArray.push("gfx/panelBarLearningLeft.gif");
imageArray.push("gfx/panelBarLearningRight.gif");

var ip = new ImagePreloader(imageArray, onPreload);