[Javascript] Foto faden van x naar y

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// 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 = [
   'images/home.jpg',
   'images/agenda.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];
}

//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
         var doc = parent.header.document;

         ixf.newimg = doc.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;
};