// JavaScript Document

var eID = "slideshow";
var imgPath = "images/";
var numImgs = 4;
var imgIdx = 0;

function startSlideshow(folder){
	imgPath = imgPath + folder + "/";
	displayImg();
}

function displayImg(){
	setOpacity(eID, 0);
	document.getElementById(eID).innerHTML = "<img src=\"" + imgPath + imgIdx + ".jpg\">";
	fadeIn(eID);
	setTimeout("fadeOut(\"" + eID + "\")", 4000);
	imgIdx = (imgIdx+1)%(numImgs);
	setTimeout("displayImg()", 5500);
}

function fadeIn(eID) {
  setOpacity(eID, 0);
	var timer = 0;
  for (var i=1; i<=100; i++) {
    setTimeout("setOpacity('"+eID+"',"+i+")", timer * 10);
  	timer++;
	}
}

function fadeOut(elt) {
  var timer = 0;
  for (var i=100; i>=1; i--) {
  	setTimeout("setOpacity('" + elt + "'," + i + ")", timer * 10);
  	timer++;
  }	
}


function fade(eID, startOpacity, stopOpacity, duration) {
	var speed = Math.round(duration / 100);
	var timer = 0;
	if (startOpacity < stopOpacity){ // fade in
		for (var i=startOpacity; i<=stopOpacity; i++) {
			setTimeout("setOpacity('"+eID+"',"+i+")", timer * speed);
			timer++;
		} return;
	}
	for (var i=startOpacity; i>=stopOpacity; i--) { // fade out
		setTimeout("setOpacity('" + eID + "'," + i + ")", timer * speed);
		timer++;
	}
}


function setOpacity(eID, opacityLevel) {
	var eStyle = document.getElementById(eID).style;
	eStyle.opacity = opacityLevel / 100;
	eStyle.filter = 'alpha(opacity='+opacityLevel+')';
}