// IXF1.11 :: Image cross-fade 
// *****************************************************
// DOM scripting by brothercake -- http://www.brothercake.com/
//******************************************************
//global object
var ixf = { 'clock' : null, 'count' : 1 }

//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
  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;
};