/* slideshow.js
 *
 * Smooth-transition slide show
 * (c) 2008 Computer Business Services, Inc.
 */

// globals
var opacity=0;
var pics=Array('banner0.jpg','banner1.jpg', 'banner2.jpg', 'banner3.jpg');
var currentPic=0;
var photoFront;
var photoBack;

// constants
var OPACITY_INCREMENT = 5; // %
var OPACITY_INTERVAL = 100; // msec
var SLIDESHOW_INTERVAL = 10000; // msec
var IMG_PATH = "images/";

// Increase opacity of the front image
function setOpacity()
{
	opacity += OPACITY_INCREMENT;
	photoFront.style.opacity = opacity / 100.0; // Mozilla/W3C CSS3
	photoFront.style.filter = 'alpha(opacity=' + opacity + ')'; // IE
	if (opacity >= 100)
	{
		opacity = 0;
		setTimeout('slideshow();', 0);
	}
	else
	{
		setTimeout('setOpacity();', OPACITY_INTERVAL);
	}
}

// Reset opacity and set next pair of images
function slideshow()
{
	photoBack.style.backgroundImage = "url('" + IMG_PATH + pics[currentPic] + "')";
	currentPic = (currentPic + 1) % pics.length;
	photoFront.style.opacity = 0;
	photoFront.style.filter = 'alpha(opacity=0)';
	photoFront.style.backgroundImage = "url('" + IMG_PATH + pics[currentPic] + "')";
	setTimeout('setOpacity()', SLIDESHOW_INTERVAL);
}