function [i,j] = ind2ij(ind, nb_line)  

   i= mod(ind, nb_line); % line number

   ind_ind = 1:length(ind);

   end_line = find(i == 0);

   if ~isempty(end_line)

       i(end_line) = nb_line;

       j(end_line) = ind(end_line)/nb_line;

       ind_ind(end_line) = [];

   end

   j(ind_ind) = floor(ind(ind_ind) /nb_line)+1;

function ind = ij2ind(i, j, nb_line)

   ind = (j-1)*nb_line+i;