// IXF1.11 :: Image cross-fade 
// *****************************************************
// DOM scripting by brothercake -- http://www.brothercake.com/
//******************************************************
//global object
var ixfs = new Hash();

function init(identifier) {
	var ixf = { 'clock' : null, 'count' : 1 }
	/*******************************************************
	
	
	
	/*****************************************************************************
	 List the images that need to be cached
	*****************************************************************************/
	
	ixf.imgs = [];
	
	/*****************************************************************************
	*****************************************************************************/
	
	
	
	//cache the images
	ixf.imgsLen = ixf.imgs.length;
	ixf.cache = [];
	for(var i=0; i<ixf.imgsLen; i++)
	{
		ixf.cache[i] = new Image;
		ixf.cache[i].src = ixf.imgs[i];
	}
	
	//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;
	};
	
	
	ixfs[identifier] = ixf;
}

//crossfade setup function
function crossfade()
{
	
	//copy the identifier argument
	var identifier = arguments[3];
	if (ixfs[identifier] == null) {
		init(identifier);
	}
	var ixf = ixfs[identifier];
		
	//if the timer is not already going
	if(ixf.clock == null)
	{
		//copy the image object 
		ixf.obj = arguments[0];
		
		//copy the image src argument 
		ixf.src = arguments[1];
		
		//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')
		{
			//weed out win/ie5.0 by testing the length of the filters collection (where filters is an object with no data)
			//then weed out mac/ie5 by testing first the existence of the alpha object (to prevent errors in win/ie5.0)
			//then the returned value type, which should be a number, but in mac/ie5 is an empty string
			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';
		}
		
		//change the image alt text if defined
		if(typeof arguments[4] != 'undefined' && arguments[4] != '')
		{
			ixf.obj.alt = arguments[4];
		}
		
		//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';
			
			ixf.newimg.id = identifier;
			
			//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) * 1000;
			
			//create fade resolution argument as 20 steps per transition
			ixf.resolution = parseInt(arguments[2], 10) * 20;
			
			//start the timer
			ixf.clock = setInterval('ixfs[\''+identifier+'\'].crossfade(\''+identifier+'\')', ixfs[identifier].length/ixfs[identifier].resolution);
		}
		
		//otherwise if opacity is not supported
		else
		{
			//just do the image swap
			ixf.obj.src = ixf.src;
		}
		
	}
};