Event.observe(window, 'load', function() {
  var ptd_top = $('diapocont')
  if (ptd_top) {
    diaporama(ptd_top, $('diapo'), '../img/portada/diapo', 2, 'appear', 3)
  }

  var ptd_top = $('diapocont2')
  if (ptd_top) {
    diaporama(ptd_top, $('diapo'), '../img/energias/diapo', 3, 'appear', 4)
  }

  var ptd_top = $('diapocont3')
  if (ptd_top) {
    diaporama(ptd_top, $('diapo'), '../img/maquinaria/stock/diapo', 3, 'appear', 4)
  }
})

function diaporama(e, i, base, counter, eff, dur, inter) {
  var count = counter + 1

  do {
   count --
   var img = document.createElement("img")
   img.src = base + count + ".jpg"
   img.id  = 'img' + count
   img.style.position = 'absolute'
   img.style.top = findPos(e)[1];
   img.style.left = findPos(e)[0];
   img.style.display = (count == 1)? 'inline' : 'none'
   img.width=e.offsetWidth;
   e.appendChild(img)
  } while (count != 1)

  setInterval(function() {
    Effect.toggle('img' + ((count == 0)? 1 : count), eff,  { duration: dur })
    Effect.toggle('img' + ((count == 0)? counter : count + 1), eff, { duration: dur })
    count = (count == (counter - 1))? 0 : count +1
  },dur * 1000);
}

// http://www.quirksmode.org/js/findpos.html
function findPos(obj) {
  var curleft = curtop = 0;
  if (obj.offsetParent) {
    do {
        curleft += obj.offsetLeft;
        curtop += obj.offsetTop;
    }
    while (obj = obj.offsetParent);
   }
   return [curleft,curtop];
}