// Keeps track of what image is being shown
 var currentImage = 0;

 // Used for controlling prev/next buttons / preloader
 var numberOfImages = galleryArray.length - 1;

 // Preload the images in imagesArray
 function preLoadImages(){
  for(i=0; i<= numberOfImages; i+1){
   imageObj = new Image();
   imageObj.src = galleryArray[i][0];
  }
 }

 // Show the previous image in imagesArray, loop to last image if currentImage is the first image
 function prevImage(){
  document.getElementById('gallery_large').src = 'loading.gif';
  if (currentImage == 0){
   whichImage = galleryArray.length - 1;
  }else{
   whichImage = currentImage-1;
  }
  document.getElementById('gallery_large').src = galleryArray[whichImage][0];
  document.getElementById('image_header_txt').innerHTML  = galleryArray[whichImage][1];
  document.getElementById('image_description').innerHTML = galleryArray[whichImage][2];
  currentImage = whichImage;
 }

 // Show the next image in galleryArray, loop to the first image if currentImage is the last image
 function nextImage(){
  document.getElementById('gallery_large').src = 'loading.gif';
  if (currentImage == galleryArray.length - 1){
   whichImage = 0;
  }else{
   whichImage = currentImage+1;
  }
  document.getElementById('gallery_large').src = galleryArray[whichImage][0];
  document.getElementById('image_header_txt').innerHTML  = galleryArray[whichImage][1];
  document.getElementById('image_description').innerHTML = galleryArray[whichImage][2];
  currentImage = whichImage;
 }

 // Show the big image for the clicked thumbnail
 function swapImage(whichImage){
  document.getElementById('gallery_large').src = 'loading.gif';
  document.getElementById('gallery_large').src = galleryArray[whichImage][0];
  document.getElementById('image_header_txt').innerHTML  = galleryArray[whichImage][1];
  document.getElementById('image_description').innerHTML = galleryArray[whichImage][2];
  currentImage = whichImage;
 }