function opacity(id, opacStart, opacEnd, millisec) {
	//speed for each frame
	var speed = Math.round(millisec / 100);
  var tmpVar = id;
	//determine the direction for the blending, if start and end are the same nothing happens
	var f= function() { tweenAlpha(opacEnd,id)};
	if (aTweenId[id] !== "undefined") clearInterval(aTweenId[id]);
	aTweenId[id] = setInterval(f,millisec);
}


function tweenAlpha(where,id){
	//id = tweenIdRoot;
//  showOnConsole(where);
	var object = document.getElementById(id).style; 
	var diff = -5;
	currOpacity = object.opacity*100;
	if (currOpacity-where != 0) {
//	alert (currOpacity);
	if (where>currOpacity) diff = 10;
	diff = Math.round(currOpacity+diff);
//	showOnConsole(diff);
	//if (diff<0) diff = 0;
	//if (diff>100) diff = 100;
	changeOpac(diff, id);
	}else{
//	showOnConsole("Done");
	clearInterval(aTweenId[id]);
	}
}


//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
	opacity(imageid,0,100,20);
	/*
	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)
}