var Fader = function (elemId, opacStart, opacEnd, millisec) {
	this.elementId = elemId;
	this.opacStart = opacStart;
	this.opacEnd=opacEnd;
	this.millisec=millisec;
	this.tmr_id = {};	
}

function opacity(id, opacStart, opacEnd, millisec) {
	//speed for each frame
	var speed = Math.round(millisec / 100);
	var timer = 0;
	var i=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--) {			
			this.tmr_id[id + "_" + i] = setTimeout("changeOpac(" + i + ",'" + id + "')" ,(timer * speed));
			timer++;
		}
	} else if(opacStart < opacEnd) {
		for(i = opacStart; i <= opacEnd; i++)
			{
			this.tmr_id[id + "_" + i] = setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));			
			timer++;
		}
	}
}

//change the opacity for different browsers
function changeOpac(opacity, id) {

	var object = document.getElementById(id).style; 

	if (object.visibility == "visible" ) {

		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)
}
*/
function play() {
	var thisObject = this;
	var opacityMethodDelegate = function() { thisObject.opacity(thisObject.elementId, thisObject.opacStart, thisObject.opacEnd, thisObject.millisec); }
	opacityMethodDelegate();
}
Fader.prototype.play = play;
Fader.prototype.opacity = opacity;
Fader.prototype.changeOpacity = changeOpac;