function opacity(id, opacStart, opacEnd, millisec) {
  //speed for each frame
  var speed = Math.round(millisec / 100);
  var timer = 0;

  //determine the direction for the blending, if start and end are the same nothing happens
  if(opacStart > opacEnd) {
    for(i = opacStart; i >= opacEnd; i--) {
      setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
      timer++;
    }
  } else if(opacStart < opacEnd) {
    for(i = opacStart; i <= opacEnd; i++)
      {
      setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
      timer++;
    }
  }
}

//change the opacity for different browsers
function changeOpac(opacity, id) {
  var object = document.getElementById(id).style; 
  object.opacity = (opacity / 100);
  object.MozOpacity = (opacity / 100);
  object.KhtmlOpacity = (opacity / 100);
  object.filter = "alpha(opacity=" + opacity + ")";
}

function shiftOpacity(id, millisec) {
  //if an element is invisible, make it visible, else make it ivisible
  if(document.getElementById(id).style.opacity == 0) {
    opacity(id, 0, 100, millisec);
  } else {
    opacity(id, 100, 0, millisec);
  }
}

function blendimage(divid, imageid, imagefile, millisec) {
  var speed = Math.round(millisec / 100);
  var timer = 0;
  
  //set the current image as background
  document.getElementById(divid).style.backgroundImage = "url(" + document.getElementById(imageid).src + ")";
  
  //make image transparent
  changeOpac(0, imageid);
  
  //make new image
  document.getElementById(imageid).src = imagefile;

  //fade in image
  for(i = 0; i <= 100; i++) {
    setTimeout("changeOpac(" + i + ",'" + imageid + "')",(timer * speed));
    timer++;
  }
}

function currentOpac(id, opacEnd, millisec) {
  //standard opacity is 100
  var currentOpac = 100;
  
  //if the element has an opacity set, get it
  if(document.getElementById(id).style.opacity < 100) {
    currentOpac = document.getElementById(id).style.opacity * 100;
  }

  //call for the function that changes the opacity
  opacity(id, currentOpac, opacEnd, millisec)
}