var coef = 0.05 ; // avancement de l'opacité
  var temps = 50 ; // temps entre chaque changement d'opacité
  var temps_pause = 3000 ; // temps d'attente entre 2 changements d'images
  //var nombre_image = 4 ; // nombre d'images a faire bouger
  //var prefix_image = '../photos/'; // chemin + prefix du nom des images
  var suffix_image = '.jpg' ; // suffix + '.extension' du nom des images
  
  // pas touche
  var indice = 2; 
  var isIE = navigator.userAgent.toLowerCase().indexOf('msie')!=-1 ;
  var img1 = null;
  var img2 = null ;
  var sens = 1;
  var tabImg; // tab contenant les images
  
  function prechargerImg(nombre_image, prefix_image)
  {
    tabImg = new Array(this.nombre_image);
    for (i=0; i<=this.nombre_image -1; i++)
    {
      tabImg[i]=new Image();
      tabImg[i].src = this.prefix_image+(i+1)+suffix_image;
    }
  }
  
  /*function init()
  {
    img1 = document.getElementById("defilement1") ;
    img2 = document.getElementById("defilement2") ;
    
    prechargerImg();
    change_opacity();
  }*/
  
  function change_opacity()
  {
    var opacity1 = 0 ;
    var opacity2 = 0 ;
    if (isIE) // for IE
    { 
      opacity1 = parseFloat(img1.filters.alpha.opacity);
      opacity2 = parseFloat(img2.filters.alpha.opacity);
    }
    else // for mozilla
    { 
      opacity1 = parseFloat(img1.style.opacity);
      opacity2 = parseFloat(img2.style.opacity);
    }
  
    if (sens)
    { 
      if (isIE) // for IE
      { 
        img1.filters.alpha.opacity = opacity1 + coef * 100;
        img2.filters.alpha.opacity = opacity2 - coef * 100;
      }
      else // for Mozilla
      { 
        img1.style.opacity = opacity1 + coef;
        img2.style.opacity = opacity2 - coef;
      }
    }
    else
    {
      if (isIE) // for IE
      { 
        img1.filters.alpha.opacity = opacity1 - coef * 100;
        img2.filters.alpha.opacity = opacity2 + coef * 100;
      }
      else // for Mozilla
      { 
        img1.style.opacity = opacity1 - coef;
        img2.style.opacity = opacity2 + coef;
      }
    }
  
    if (isIE) // for IE
    { 
      opacity1 = parseFloat(img1.filters.alpha.opacity);
      opacity2 = parseFloat(img2.filters.alpha.opacity);
    }
    else // for mozilla
    { 
      opacity1 = parseFloat(img1.style.opacity);
      opacity2 = parseFloat(img2.style.opacity);
    }
  
    if (opacity2 <= 0)
    { 
      img2.src=tabImg[indice++].src;
      sens = 0;
      if (indice == (tabImg.length)) indice=0;
      window.setTimeout("change_opacity()",temps_pause) ;
      return 0;
    }
    else if (opacity1 <= 0)
    { 
      img1.src=tabImg[indice++].src;
      sens = 1;
      if (indice == (tabImg.length)) indice=0;
      window.setTimeout("change_opacity()",temps_pause) ;
      return 0;
    }
    window.setTimeout("change_opacity()",temps) ; 
  }