function afficher(calque) {
    var calbis;
    calbis = calque.concat("_vide");

    hiddenByClass('packimage', document, '*');

    if (document.getElementById) {
        document.getElementById(calque).style.visibility = "visible";
        document.getElementById(calque).style.display = "block";
    }
    if (document.all && !document.getElementById) {
        document.all[calque].style.visibility = "visible";
        document.all[calque].style.display = "block";
    }
    if (document.layers) {
        document.layers[calque].visibility = "visible";
        document.layers[calque].display = "block";
    }

}

function enlever(calque) {

    if (document.getElementById) {
        document.getElementById(calque).style.visibility = "hidden";
        document.getElementById(calque).style.display = "none";
    }
    if (document.all && !document.getElementById) {
        document.all[calque].style.visibility = "hidden";
        document.all[calque].style.display = "none";
    }
    if (document.layers) {
        document.layers[calque].visibility = "hidden";
        document.layers[calque].display = "none";
    }
}

function getElementsByClass(searchClass, node, tag) {
    var classElements = new Array();
    if (node == null) node = document;
    if (tag == null) tag = '*';

    var els = node.getElementsByTagName(tag);
    var elsLen = els.length;
    var pattern = new RegExp("(^|\\s)" + searchClass + "(\\s|$)");

    for (i = 0, j = 0; i < elsLen; i++) {
        if (pattern.test(els[i].className)) {
            classElements[j] = els[i];
            j++;
        }
    }

    return classElements;
}


function hiddenByClass(searchClass, node, tag) {

    var elm = getElementsByClass(searchClass, node, tag);

    for (var i = 0; i < elm.length; i++) {
        elm[i].style.display = "none";
    }
}