function changerImageAccueil() {
    var n = 4   // 4 images affichées dans le bandeau
    var j = 1 + Math.round(Math.random() * (n - 1));
    eteindreImage('imgAccueil'+j, 100);
}

function changerImage(oImg) {
    var imgElt1 = document.getElementById('imgAccueil5');
    var imgElt2 = oImg;
    var srcMemo = imgElt1.src;
    imgElt1.src = imgElt2.src;
    imgElt2.src = srcMemo;
    
    var aElt1 = document.getElementById('aAccueil5');
    var aElt2 = document.getElementById(oImg.id.replace('img','a'));
    var hrefMemo = aElt1.href;
    aElt1.href = aElt2.href;
    aElt2.href = hrefMemo;
    var onclickMemo = aElt1.onclick;
    aElt1.onclick = aElt2.onclick;
    aElt2.onclick = onclickMemo;
}

function allumerImage(imgId, opacite) {
    oImg = document.getElementById(imgId);
    opacite++;
    if (opacite >= 100) {
        setTimeout("changerImageAccueil()", 3000);
        return true;
    }
    fixerOpacite(oImg, opacite);
    setTimeout("allumerImage('"+imgId+"', "+opacite+")", 10);
}

function eteindreImage(imgId, opacite) {
    oImg = document.getElementById(imgId);
    opacite--;
    if (opacite <= 0) {
        changerImage(oImg);
        allumerImage(imgId, opacite);
        return true;
    }
    fixerOpacite(oImg, opacite);
    setTimeout("eteindreImage('"+imgId+"', "+opacite+")", 10);
}

function fixerOpacite(elt, opacite) {
    if (document.all) {
        // IE
        elt.filters.alpha.opacity = opacite;
    } else {
        // FF
        elt.style.setProperty("-moz-opacity", opacite / 100, "");
    }
 }