/*
	Image Cross Fade Redux
	Version 1.0
	Last revision: 02.15.2006
	steve@slayeroffice.com

	Rewrite of old code found here: http://slayeroffice.com/code/imageCrossFade/index.html


	<img
		src="terra.jpg"
		alt="Terra"
		title="HTML.it"
		onclick="parent.location='http://www.html.it'"
	/>
	<img
		src="fuoco.jpg"
		alt="Fuoco"
		title="HTML.it - CSS"
		onclick="parent.location='http://css.html.it'"
	/>
	<img
		src="aria.jpg"
		alt="Aria"
		title="HTML.it - Javascript"
		onclick="parent.location='http://javascript.html.it'"
	/>
	<img
		src="acqua.jpg"
		alt="Acqua"
		title="HTML.it - PHP"
		onclick="parent.location='http://php.html.it'"
	/>

*/

/** Preserva gli eventi di onload della pagina */
window.addEventListener?window.addEventListener('load',slideshowInit,false):window.attachEvent('onload',slideshowInit);

/** Pagina, immagini della slideshow, immagine corrente */
var d=document, imgs=new Array(), current=0; //pause=false, zInterval=null
/** Durata di ciascuna immagine, in millisecondi */
var slideshowDelay = 3000;
/** Durata dell'effetto di transizione */
var slideshowFade = 25;

/**
 * Inizializza la slideshow
 */
function slideshowInit() {
	if ((!d.getElementById) || (!d.createElement)) {
		return;
	}

	css = d.createElement('link');
	//css.setAttribute('href','css/slideshow2.css');
	css.setAttribute('rel','stylesheet');
	css.setAttribute('type','text/css');
	d.getElementsByTagName('head')[0].appendChild(css);

	imgs = d.getElementById('slideshow').getElementsByTagName('img');
	for (i = 1; i < imgs.length; i++) {
		imgs[i].xOpacity = 0;
		imgs[i].style.position = 'absolute';
		imgs[i].style.display = 'none';
		imgs[i].style.top = '0';
		imgs[i].style.left = '0';
	}
	imgs[0].style.display = 'block';
	imgs[0].xOpacity = .99;
	setTimeout(slideshowStart,slideshowDelay / 3);
}



/**
 * Loop di esecuzione della slideshow
 */
function slideshowStart() {
	cOpacity = imgs[current].xOpacity;
	nIndex = imgs[current+1] ? current + 1 : 0;
	nOpacity = imgs[nIndex].xOpacity;

	cOpacity -= .05;
	nOpacity += .05;

	imgs[nIndex].style.display = 'block';
	imgs[current].xOpacity = cOpacity;
	imgs[nIndex].xOpacity = nOpacity;

	slideshowOpacity(imgs[current]);
	slideshowOpacity(imgs[nIndex]);

	if (cOpacity <= 0) {
		imgs[current].style.display = 'none';
		current = nIndex;
		setTimeout(slideshowStart,slideshowDelay);
	}
	else {
		setTimeout(slideshowStart,slideshowFade);
	}

}



/**
 * Cambia l'opacità dell'immagine per creare l'effetto di dissolvenza
 */
function slideshowOpacity(obj) {
	if (obj.xOpacity > .99) {
		obj.xOpacity = .99;
		return;
	}

	obj.style.opacity = obj.xOpacity;
	obj.style.MozOpacity = obj.xOpacity;
	obj.style.filter = 'alpha(opacity=' + (obj.xOpacity * 100) + ')';
}