function Permut (flag,img) {
   if (document.images) {
        if (document.images[img].permloaded) {
            if (flag==1) document.images[img].src = document.images[img].perm.src
            else document.images[img].src = document.images[img].perm.oldsrc
        }
   }
}
function preloadPermut (img,adresse) {
   if (document.images) {
        img.onload = null;
        img.perm = new Image ();
        img.perm.oldsrc = img.src;
        img.perm.src = adresse;
        img.permloaded = true;
   }
}