// IXF1.11 :: Image cross-fade
// *****************************************************
// DOM scripting by brothercake -- http://www.brothercake.com/
//******************************************************
//global object
var ixf = { 'clock' : null, 'count' : 1 }
//crossfade setup function
function crossfade(){
	//copy the image object 
	ixf.obj = arguments[0];
	//copy the image src argument 
	ixf.src = arguments[1];
	//change the image alt text if defined
	if(typeof arguments[3] != 'undefined' && arguments[3] != ''){
		ixf.obj.alt = arguments[3];
	}
	//if the timer is not already going
	if(ixf.clock == null){
		//store the supported form of opacity
		if(typeof ixf.obj.style.opacity != 'undefined'){
				ixf.type = 'w3c';
			} else if(typeof ixf.obj.style.MozOpacity != 'undefined') {
				ixf.type = 'moz';
			} else if(typeof ixf.obj.style.KhtmlOpacity != 'undefined')	{
				ixf.type = 'khtml';
			} else if(typeof ixf.obj.filters == 'object') { 
				ixf.type = (ixf.obj.filters.length > 0 && typeof ixf.obj.filters.alpha == 'object' && typeof ixf.obj.filters.alpha.opacity == 'number') ? 'ie' : 'none';
			} else {
				ixf.type = 'none';
		}
		
		//if any kind of opacity is supported
		if(ixf.type != 'none'){
			//create a new image object and append it to body detecting support for namespaced element creation, in case we're in the XML DOM
			ixf.newimg = document.getElementsByTagName('body')[0].appendChild((typeof document.createElementNS != 'undefined') ? document.createElementNS('http://www.w3.org/1999/xhtml', 'img') : document.createElement('img'));
			//set positioning classname
			ixf.newimg.className = 'idupe';
			//set id name
			ixf.newimg.setAttribute("id", "idupe");
			//set src to new image src
			ixf.newimg.src = ixf.src
			//move it to superimpose original image
			ixf.newimg.style.left = ixf.getRealPosition(ixf.obj, 'x') + 'px';
			ixf.newimg.style.top = ixf.getRealPosition(ixf.obj, 'y') + 'px';
			//copy and convert fade duration argument 
			ixf.length = parseInt(arguments[2], 10) * 1;
			//create fade resolution argument as 20 steps per transition
			ixf.resolution = parseInt(arguments[2], 10) * 20;
			//start the timer
			ixf.clock = setInterval('ixf.crossfade()', ixf.length/ixf.resolution);
		} else {  
			 //otherwise if opacity is not supported just do the image swap 
			ixf.obj.src = ixf.src;
		}
	} else {
		//Timer is busy just do the image swap
		ixf.obj.src = ixf.src;
	}
};


//crossfade timer function
ixf.crossfade = function(){
	//decrease the counter on a linear scale
	ixf.count -= (1 / ixf.resolution);
	
	//if the counter has reached the bottom
	if(ixf.count < (1 / ixf.resolution)){
		//clear the timer
		clearInterval(ixf.clock);
		ixf.clock = null;
		//reset the counter
		ixf.count = 1;
		//set the original image to the src of the new image
		ixf.obj.src = ixf.src;
	}
	
	//set new opacity value on both elements using whatever method is supported
	switch(ixf.type){
		case 'ie' :
			ixf.obj.filters.alpha.opacity = ixf.count * 100;
			ixf.newimg.filters.alpha.opacity = (1 - ixf.count) * 100;
			break;
		case 'khtml' :
			ixf.obj.style.KhtmlOpacity = ixf.count;
			ixf.newimg.style.KhtmlOpacity = (1 - ixf.count);
			break;
		case 'moz' : 
			//restrict max opacity to prevent a visual popping effect in firefox
			ixf.obj.style.MozOpacity = (ixf.count == 1 ? 0.9999999 : ixf.count);
			ixf.newimg.style.MozOpacity = (1 - ixf.count);
			break;
		default : 
			//restrict max opacity to prevent a visual popping effect in firefox
			ixf.obj.style.opacity = (ixf.count == 1 ? 0.9999999 : ixf.count);
			ixf.newimg.style.opacity = (1 - ixf.count);
	}
	
	//now that we've gone through one fade iteration  we can show the image that's fading in
	ixf.newimg.style.visibility = 'visible';
	//keep new image in position with original image in case text size changes mid transition or something
	ixf.newimg.style.left = ixf.getRealPosition(ixf.obj, 'x') + 'px';
	ixf.newimg.style.top = ixf.getRealPosition(ixf.obj, 'y') + 'px';
	
	//if the counter is at the top, which is just after the timer has finished
	if(ixf.count == 1){
		//remove the duplicate image
		ixf.newimg.parentNode.removeChild(ixf.newimg);
	}
};

//get real position method
ixf.getRealPosition = function(){
	this.pos = (arguments[1] == 'x') ? arguments[0].offsetLeft : arguments[0].offsetTop;
	this.tmp = arguments[0].offsetParent;
	while(this.tmp != null){
		this.pos += (arguments[1] == 'x') ? this.tmp.offsetLeft : this.tmp.offsetTop;
		this.tmp = this.tmp.offsetParent;
	}
	return this.pos;
};