var posArr=new Array(1,2,3,4);		// Memorizzo le prime 4 immagini utilizzate

// Funzione che randomizza le immagini del menu superiore
function rnd_immagine(cartella,totImg) { 
	var pos=0;
	var numImg=0;
		
	pos=Math.floor(Math.random()*4+1);				// Posizione
	numImg=Math.floor(Math.random()*totImg+1);		// Numero immagine
	
	// Controllo utilizzo img
	while (!controllaUtilizzoImg(numImg)){
		numImg=Math.floor(Math.random()*totImg+1);
	}
	
	//alert(numImg);
	
	posArr[pos-1]=numImg;		// Memorizzo l'immagine utilizzata nella posizione
	
	//alert('img/' + cartella + '/' + numImg + '.jpg');
	
	//alert(cartella);
	
	blendimage('blenddiv' + pos,'blendimage' + pos, 'img/' + cartella + '/' + numImg + '.jpg',4000);

	//setTimeout('rnd_immagine(cartella,totImg)',5000);
	
	setTimeout("rnd_immagine('" + cartella + "'," + totImg + ")",5000);

} 

function controllaUtilizzoImg(numero){
	// Controllo presenza immagine doppia
	for(i=0;i<4;i++){
		if (posArr[i]==numero)
			return false;
	}
	
	return true;
}

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)
}