//if an element is invisible, make it visible, else make it invisible

function initial (opacity, id) { 
    var object = document.getElementById(id).style; 
    object.opacity = 0; 
    object.MozOpacity = 0; 
    object.KhtmlOpacity = 0; 
    object.filter = "alpha(opacity=" + opacity + ")"; 
}

function blenden(id, millisec) { 
    if(document.getElementById(id).style.opacity == 0) { 
        opacity(id, 0, 100, millisec); 
    } else { 
        opacity(id, 100, 0, millisec); 
    } 
}

function opacity(id, opacStart, opacEnd, millisec) { 
    //speed for each frame 
    var speed = Math.round(millisec / 100); 
    var timer = 0; 

    //determine the direction for the blending, if start and end are the same nothing happens 
    if(opacStart > opacEnd) { 
        for(i = opacStart; i >= opacEnd; i--) { 
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed)); 
            timer++; 
        } 
    } else if(opacStart < opacEnd) { 
        for(i = opacStart; i <= opacEnd; i++) 
            { 
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed)); 
            timer++; 
        } 
    } 
} 

//change the opacity for different browsers 
function changeOpac(opacity, id) { 
    var object = document.getElementById(id).style; 
    object.opacity = (opacity / 100); 
    object.MozOpacity = (opacity / 100); 
    object.KhtmlOpacity = (opacity / 100); 
    object.filter = "alpha(opacity=" + opacity + ")"; 
}

function submenu_an(id) {
	document.getElementById(id).style.visibility='visible'
}
function submenu_aus(id) {
	document.getElementById(id).style.visibility='hidden'
}

// Navigation Bilder
orchester = new Image(); orchester.src = "./bilder/navigation/orchester.gif";
orchester_over = new Image(); orchester_over.src = "./bilder/navigation/orchester_over.gif";

konzerte = new Image(); konzerte.src = "./bilder/navigation/konzerte.gif";
konzerte_over = new Image(); konzerte_over.src = "./bilder/navigation/konzerte_over.gif";

diskografie = new Image(); diskografie.src = "./bilder/navigation/diskografie.gif";
diskografie_over = new Image(); diskografie_over.src = "./bilder/navigation/diskografie_over.gif";

presse = new Image(); presse.src = "./bilder/navigation/presse.gif";
presse_over = new Image(); presse_over.src = "./bilder/navigation/presse_over.gif";

foerderverein = new Image(); foerderverein.src = "./bilder/navigation/foerderverein.gif";
foerderverein_over = new Image(); foerderverein_over.src = "./bilder/navigation/foerderverein_over.gif";

kontakt = new Image(); kontakt.src = "./bilder/navigation/kontakt.gif";
kontakt_over = new Image(); kontakt_over.src = "./bilder/navigation/kontakt_over.gif";

impressum = new Image(); impressum.src = "./bilder/navigation/impressum.gif";
impressum_over = new Image(); impressum_over.src = "./bilder/navigation/impressum_over.gif";
	
// mouse-over
function over(id){
	{document[id].src = eval(id+"_over.src");}
}

// mouse-out (falls passiv)
function out(id){
	{document[id].src = eval(id+".src");}
}

// mouse-out (falls aktiv)
function out_aktiv(id){
	{document[id].src = eval(id+"_aktiv.src");}
}