// IXF1.11 :: Image cross-fade 

// *****************************************************

// DOM scripting by brothercake -- http://www.brothercake.com/

//******************************************************

//global object

var ixf = { 'clock' : null, 'count' : 1 }

/*******************************************************







/*****************************************************************************

 List the images that need to be cached

*****************************************************************************/



ixf.imgs = [

	'buttons/udm4-whitebutton88x31.gif',

	'buttons/udm4-greenbutton88x31.gif',

	'buttons/udm4-purplebutton88x31.gif'

	];



/*****************************************************************************

*****************************************************************************/







//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 setup function

function crossfade()

{

	//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[3] != 'undefined' && arguments[3] != '')

		{

			ixf.obj.alt = arguments[3];

		}

		

		//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 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('ixf.crossfade()', ixf.length/ixf.resolution);

		}

		

		//otherwise if opacity is not supported

		else

		{

			//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
ixf.newimg.style.width = '550px';
	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';
	ixf.newimg.style.width = '550px';

	

	//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;

};