velocita = 300;

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++;
		}
	}
}

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 blendimageOut(divid, imageid, imagefile) {

    var speed = Math.round(velocita / 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 blendimage(divid, imageid, imagefile) {
    var speed = Math.round(velocita / 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)
}