var ImageBanners = {
    lastImage:1,
    lastImageValue:null,
    imageValues:[]
}

function Bannerchange () {
               
    var img1   = document.getElementById('header_img1');
    var img2   = document.getElementById('header_img2');
                
    var interval2 = null;
    var imgChanged = false;
               
    var opa1  = 1;
    var opa2  = 0;
        
    function changeImage () {
        opa1 -= 0.02;
        opa2 += 0.02;             
                
        if(opa1 < 0) {
            window.clearInterval(interval2);

            /**
                                 * cookie speichern mit dem letzten bild
                                 */
            var cookieContent = 'li='+(ImageBanners.lastImage)+'&lis='+ImageBanners.imageValues[ImageBanners.lastImage];                                 
            document.cookie = cookieContent+';path=/';            
             
            /**
                                * neues Bild aus dem Pool ziehen 
                                */
            if(ImageBanners.lastImage >= ImageBanners.imageValues.length-1) {
                ImageBanners.lastImage = 0;
            } else {
                ImageBanners.lastImage++;
            }
            
            var buffer = img1.src;            
                
            if(!imgChanged) { 
                
                img1   = document.getElementById('header_img2');
                img2   = document.getElementById('header_img1');
                
                img2.src = ImageBanners.imageValues[ImageBanners.lastImage];
                                
                imgChanged = true;
            } else {
                img1   = document.getElementById('header_img1');
                img2   = document.getElementById('header_img2');
                imgChanged = false;
                
                img2.src = ImageBanners.imageValues[ImageBanners.lastImage];
            }
                                     
            opa1 = 1;
            opa2 = 0;   
                       
            window.setTimeout(changer,8000);
                        
        } else {
                    
            if(navigator.appName == 'Microsoft Internet Explorer') {
                        
                oc1 = opa1 * 100;
                oc2 = opa2 * 100;
                        
                img1.style.filter="Alpha(opacity="+oc1+", finishopacity=0)";
                img2.style.filter="Alpha(opacity="+oc2+", finishopacity=0)";
            } else {
                img1.style.opacity = opa1;
                img2.style.opacity = opa2;
            }
        }
    }
                
    function changer() {        
        interval2 = window.setInterval(changeImage,50);
    }
           
    /**
             * PHP Server hat Bilder als String zurück gesendet und wird anhand des Trennzeichens # in ein Array zerlegt
             *@access private
             *@param String ImageBanners.imageValues as String
             *@return void
             */             
    function imagesLoaded (result) {
    
        ImageBanners.imageValues = result.split('#'); 
        
        img1.src = ImageBanners.imageValues[ImageBanners.lastImage];
        
        var i2 = (ImageBanners.lastImage+1 <= ImageBanners.imageValues.length)?++ImageBanners.lastImage:0;
        img2.src = ImageBanners.imageValues[i2];
        
        window.setTimeout(changer,8000);  
    }
                
    this.init = function () {    
        // get Banners 
        var bannerLoader = new AjaxRequest('index.php?action=Bannerchange');
            bannerLoader.setSendMethod('POST');
            bannerLoader.setCallBack(imagesLoaded);
            bannerLoader.initLoad();                 
    }
}