// JavaScript Document
//global object

var isf = { 'clock' : null, 'fade' : true, 'count' : 1 };

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







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

 List the images that need to be cached

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

// Modified by Jack Collins 2007-04-21

// photos must be set inside including script. 

isf.imgs = photos;





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

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







//cache the images

isf.imgsLen = isf.imgs.length;

isf.cache = [];

for(var i=0; i<isf.imgsLen; i=i+1)

{

	isf.cache[i] = new Image;

	isf.cache[i].src = isf.imgs[i];

}





//swapfade setup function

function swapfade()

{

	//if the timer is not already going

	if(isf.clock === null)

	{

		//copy the image object 

		isf.obj = arguments[0];

		

		//copy the image src argument 

		isf.src = arguments[1];

		

		//store the supported form of opacity

		if(typeof isf.obj.style.opacity != 'undefined')

		{

			isf.type = 'w3c';

		}

		else if(typeof isf.obj.style.MozOpacity != 'undefined')

		{

			isf.type = 'moz';

		}

		else if(typeof isf.obj.style.KhtmlOpacity != 'undefined')

		{

			isf.type = 'khtml';

		}

		else if(typeof isf.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

			isf.type = (isf.obj.filters.length > 0 && typeof isf.obj.filters.alpha == 'object' && typeof isf.obj.filters.alpha.opacity == 'number') ? 'ie' : 'none';

		}

		else

		{

			isf.type = 'none';

		}

		

		//change the image alt text if defined

		if(typeof arguments[3] != 'undefined' && arguments[3] !== '')

		{

			isf.obj.alt = arguments[3];

		}

		

		//if any kind of opacity is supported

		if(isf.type != 'none')

		{

			//copy and convert fade duration argument 

			//the duration specifies the whole transition

			//but the swapfade is two distinct transitions

			isf.length = parseInt(arguments[2], 10) * 500;

			

			//create fade resolution argument as 20 steps per transition

			//again, split for the two distrinct transitions

			isf.resolution = parseInt(arguments[2], 10) * 10;

			

			//start the timer

			isf.clock = setInterval('isf.swapfade()', isf.length/isf.resolution);

		}

		

		//otherwise if opacity is not supported

		else

		{

			//just do the image swap

			isf.obj.src = isf.src;

		}

		

	}

};



//swapfade timer function

isf.swapfade = function()

{

	//increase or reduce the counter on an exponential scale

	isf.count = (isf.fade) ? isf.count * 0.9 : (isf.count * (1/0.9)); 

	

	//if the counter has reached the bottom

	if(isf.count < (1 / isf.resolution))

	{

		//clear the timer

		clearInterval(isf.clock);

		isf.clock = null;



		//do the image swap

		isf.obj.src = isf.src;



		//reverse the fade direction flag

		isf.fade = false;

		

		//restart the timer

		isf.clock = setInterval('isf.swapfade()', isf.length/isf.resolution);



	}

	

	//if the counter has reached the top

	if(isf.count > (1 - (1 / isf.resolution)))

	{

		//clear the timer

		clearInterval(isf.clock);

		isf.clock = null;



		//reset the fade direction flag

		isf.fade = true;

		

		//reset the counter

		isf.count = 1;

	}



	//set new opacity value on element

	//using whatever method is supported

	switch(isf.type)

	{

		case 'ie' :

			isf.obj.filters.alpha.opacity = isf.count * 100;

			break;

			

		case 'khtml' :

			isf.obj.style.KhtmlOpacity = isf.count;

			break;

			

		case 'moz' : 

			//restrict max opacity to prevent a visual popping effect in firefox

			isf.obj.style.MozOpacity = (isf.count == 1 ? 0.9999999 : isf.count);

			break;

			

		default : 

			//restrict max opacity to prevent a visual popping effect in firefox

			isf.obj.style.opacity = (isf.count == 1 ? 0.9999999 : isf.count);

	}

};