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



/*****************************************************************************
 List the images that need to be cached
*****************************************************************************/

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



//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)
    {
        
        if(typeof ixf.fix != 'undefined'){
            ixf.fix.remove();
        }
        
        //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 = (navigator.appName == 'Microsoft Internet Explorer') ? 'ie' : 'none';
            
            // Dead code
            //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;
        
        ixf.fix = new Element('img',{'src':ixf.src,'id':'fixidupe','style':'position:absolute;margin-left:0px;margin-top:0px;'});
        ixf.obj.insert({after: ixf.fix});
        //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' :
            
            // New Script (Working) idea from "http://www.cryer.co.uk/resources/javascript/script19_fade_image.htm#self"
            ixf.obj.style.filter = 'alpha(opacity=' + (ixf.count * 100) + ')';
            ixf.newimg.style.filter = 'alpha(opacity=' + ((1 - ixf.count) * 100) + ')';
            
            // Original Script (Not Working)
            //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;
};