// ------------------------ Classe per creare dissolvenze incrociate tra immacini compatibile con il mac -----------------------------

/*
----------------------------------------- ESEMPIO DI CHIAMATA  IN UNA PAGINA HTML o ASP ---------------------------------------------------------

<script type="text/javascript" src="/functions/blendtrans.js"></script>

<div style="background-image: url(03.jp_); background-repeat: no-repeat; width: 1000x; height: 620px;" id="blenddiv">
		<img src="images/site/01.jpg" alt="" width="1000" height="620" id="blendimage" style="width: 1000px; height: 620px; border: 0 none; filter: alpha(opacity=0); -moz-opacity: 0; opacity: 0;" /><br />
</div>


<script language="javascript">
//-------------------------------  FUNZIONE PER CREARE DISSOLVENZE INCROCIATE TRA IMMAGINI MAC COMPATIBILI -------------------------------------------

function crossFadeStart(){
	var randomnumber=Math.floor(Math.random()*4)
	//alert(randomnumber)
	blendimage('blenddiv','blendimage', '/images/site/0'+ randomnumber +'.jpg',600)
}
t = setInterval("crossFadeStart()", 600)

//---------------------------------------------------------------------------------------------------------------------------------------------

</script>

------------------------------------------------------------------------------------------------------------------------

*/


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)
}