var seq_constat=0;
var seq_intervention=0; 
var seq_fin=0;
i=0; 
function travaux_changer_image(rubrique,nbre_images)
{
for ( var i = 1 ; i <= nbre_images ; i++ ) { 
    if ( document.getElementById(rubrique+i) ) { 
        document.getElementById(rubrique+i).style.display='none'; 
    } 
}
  if (rubrique=='image_avant_')
  {
  if (seq_constat==nbre_images-1)
  {
  seq_constat=0; i=1;
  }
  else 
  {
  seq_constat++;
  i=seq_constat+1;
  }
  }
  if (rubrique=='image_pendant_')
  {
  if (seq_intervention==nbre_images-1)
  {
  seq_intervention=0; i=1;
  }
  else 
  {
  seq_intervention++;
  i=seq_intervention+1;
  }
  }
  if (rubrique=='image_apres_')
  {
  if (seq_fin==nbre_images-1)
  {
  seq_fin=0; i=1;
  }
  else 
  {
  seq_fin++;
  i=seq_fin+1;
  }
  }
document.getElementById(rubrique+i).style.display='block';
}