// IXF1.11 :: Image cross-fade
// *****************************************************
// DOM scripting by brothercake -- http://www.brothercake.com/
//******************************************************

var Ixf = function(pictures) {

//global object
  this.clock = null;
  this.count =  1;
  this.counter = 0;
  this.currentNumber = 0;
/*****************************************************************************
 List the images that need to be cached
*****************************************************************************/

  var oThis = this;
  oThis.imgs = pictures;

  this.cacheImages = function () {

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

	//cache the images
	oThis.imgsLen = oThis.imgs.length;
	oThis.cache = [];
	for(var i=0; i<oThis.imgsLen; i++)
	{
		oThis.cache[i] = new Image;
		oThis.cache[i].src = oThis.imgs[i];
	}

  }

//crossfade setup function
  this.crossfade = function () {

	oThis.counter++;

	oThis.currentNumber = (oThis.counter%(oThis.imgsLen));

	//if the timer is not already going
	if(oThis.clock == null)
	{
		//copy the image object
		oThis.obj = arguments[0];

        //copy the image src argument
		if(typeof arguments[3] != 'undefined' && arguments[3] != '') {
    		oThis.src = oThis.imgs[arguments[3]];
	    } else {
            oThis.src = oThis.imgs[oThis.currentNumber];
	    }

		//store the supported form of opacity
		if(typeof oThis.obj.style.opacity != 'undefined')
		{
			oThis.type = 'w3c';
		}
		else if(typeof oThis.obj.style.MozOpacity != 'undefined')
		{
			oThis.type = 'moz';
		}
		else if(typeof oThis.obj.style.KhtmlOpacity != 'undefined')
		{
			oThis.type = 'khtml';
		}
		else if(typeof oThis.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
			oThis.type = (oThis.obj.filters.length > 0 && typeof oThis.obj.filters.alpha == 'object' && typeof oThis.obj.filters.alpha.opacity == 'number') ? 'ie' : 'none';
		}
		else
		{
			oThis.type = 'none';
		}

		//change the image alt text if defined
		if(typeof arguments[2] != 'undefined' && arguments[2] != '')
		{
			oThis.obj.alt = arguments[2];
		}

		//if any kind of opacity is supported
		if(oThis.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
			oThis.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
			oThis.newimg.className = 'idupe';

			//set src to new image src
			oThis.newimg.src = oThis.src

			//move it to superimpose original image
			oThis.newimg.style.left = oThis.getRealPosition(oThis.obj, 'x') + 'px';
			oThis.newimg.style.top = oThis.getRealPosition(oThis.obj, 'y') + 'px';

			//copy and convert fade duration argument
			var kk = 1;
			if ( typeof arguments[1] != 'undefined' && arguments[1] != '')
			  kk = arguments[1];
			else
			  kk = 1;
			oThis.length = kk * 1000;

			//create fade resolution argument as 20 steps per transition
			oThis.resolution = kk * 22;

			//start the timer
			oThis.clock = setInterval(oThis.crossfadestep, oThis.length/oThis.resolution);
		}

		//otherwise if opacity is not supported
		else
		{
			//just do the image swap
			oThis.obj.src = oThis.src;
		}

	}
  }


//crossfade timer function
  this.crossfadestep = function() {
	//decrease the counter on a linear scale
	oThis.count -= (1 / oThis.resolution);

	//if the counter has reached the bottom
	if(oThis.count < (1 / oThis.resolution))
	{
		//clear the timer
		clearInterval(oThis.clock);
		oThis.clock = null;

		//reset the counter
		oThis.count = 1;

		//set the original image to the src of the new image
		oThis.obj.src = oThis.src;
	}

	//set new opacity value on both elements
	//using whatever method is supported
	switch(oThis.type)
	{
		case 'ie' :
			oThis.obj.filters.alpha.opacity = oThis.count * 100;
			oThis.newimg.filters.alpha.opacity = (1 - oThis.count) * 100;
			break;

		case 'khtml' :
			oThis.obj.style.KhtmlOpacity = oThis.count;
			oThis.newimg.style.KhtmlOpacity = (1 - oThis.count);
			break;

		case 'moz' :
			//restrict max opacity to prevent a visual popping effect in firefox
			oThis.obj.style.MozOpacity = (oThis.count == 1 ? 0.9999999 : oThis.count);
			oThis.newimg.style.MozOpacity = (1 - oThis.count);
			break;

		default :
			//restrict max opacity to prevent a visual popping effect in firefox
			oThis.obj.style.opacity = (oThis.count == 1 ? 0.9999999 : oThis.count);
			oThis.newimg.style.opacity = (1 - oThis.count);
	}

	//now that we've gone through one fade iteration
	//we can show the image that's fading in
	oThis.newimg.style.visibility = 'visible';

	//keep new image in position with original image
	//in case text size changes mid transition or something
	oThis.newimg.style.left = oThis.getRealPosition(oThis.obj, 'x') + 'px';
	oThis.newimg.style.top = oThis.getRealPosition(oThis.obj, 'y') + 'px';

	//if the counter is at the top, which is just after the timer has finished
	if(oThis.count == 1)
	{
		//remove the duplicate image
		oThis.newimg.parentNode.removeChild(oThis.newimg);
	}
  }



//get real position method
  this.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;
  }
}