var num=0;

imgArray = [
  ['./images/windowcasings/image003.jpg','',''],
  ['./images/windowcasings/image005.jpg','',''],
  ['./images/windowcasings/image007.jpg','',''],
  ['./images/windowcasings/image009.jpg','',''],
  ['./images/windowcasings/image011.jpg','',''],
  ['./images/windowcasings/image013.jpg','',''],
  ['./images/windowcasings/image015.jpg','',''],
  ['./images/windowcasings/image017.jpg','',''],
  ['./images/windowcasings/image019.jpg','','']
]

function slideshow(slide_num) {
  document.getElementById('mypic').src=imgArray[slide_num][0];
  document.getElementById('mypic').alt=imgArray[slide_num][1];
  document.getElementById('burns').innerHTML=imgArray[slide_num][2];
}

function slideshowUp() {
  num++;
  num = num % imgArray.length;
  slideshow(num);
}

function slideshowBack() {
  num--;
  if (num < 0) {num=imgArray.length-1;}
  num = num % imgArray.length;
  slideshow(num);
}