// IXF1.0 :: 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 = [
	'images/homephotos/seals.jpg',
	'images/homephotos/crab.jpg',
	//'images/homephotos/deckwork.jpg',
	'images/homephotos/nets.jpg',
	'images/homephotos/studentf.jpg',
	'images/homephotos/trinidad.jpg',
	'images/homephotos/microscopes.jpg',
	'images/homephotos/collection.jpg',
	'images/homephotos/sunset.jpg'
	];

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



//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];
}

//setup for cycling images-- added by ajs
var imgs1 = new Array("images/homephotos/seals.jpg","images/homephotos/crab.jpg","images/homephotos/nets.jpg","images/homephotos/studentf.jpg","images/homephotos/trinidad.jpg","images/homephotos/microscopes.jpg","images/homephotos/collection.jpg","images/homephotos/sunset.jpg")
var alts1 = new Array("Seals congregate around a buoy in the ocean.","Female student holds a live crab on the deck of the Coral Sea.","Students conducting experiments on the Research Vessel Coral Sea.","Collecting samples on the Research Vessel Coral Sea.","Female student posing on the deck of the Research Vessel Coral Sea.","Students walking down the hill to the ocean from the HSU Marine Laboratory in Trinidad.","Students inspect samples using microscopes in the lab.","Studentts retrieve samples on the deck of the Coral Sea Research Vessel.","Sunset over Humboldt Bay from the deck of the Coral Sea.")
var currentAd1 = 7
var imgCt1 = 8


//crossfade setup function
function crossfade()
{
	setTimeout("crossfade()",6 * 1000) 
	//loop images-- added by ajs
	 currentAd1++
  if (currentAd1 == imgCt1) 
  {
    currentAd1 = 0
  }
	  
  
	//if the timer is not already going
	if(ixf.clock == null)
	{
		//copy the image object 
		ixf.obj = document.getElementById('test');
		
		//copy the image src argument 
		ixf.src = imgs1[currentAd1];
		
		//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 alts1[currentAd1] != 'undefined' && alts1[currentAd1] != '')
		{
			ixf.obj.alt = alts1[currentAd1];
		}
		
		//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.getElementById('RotatingPhotos').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(3, 10) * 1000;
			
			//create fade resolution argument as 20 steps per transition
			ixf.resolution = parseInt(3, 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
	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' : 
			ixf.obj.style.MozOpacity = ixf.count;
			ixf.newimg.style.MozOpacity = (1 - ixf.count);
			break;
			
		default : 
			ixf.obj.style.opacity = 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;
};