function [H] = Histo(I);
     [nblig,nbcol] = size(I);
     H = zeros(1,256);
     for lig = 1 : nblig
          for col = 1 : nbcol
               ng = double(I(lig,col) + 1);
               H(ng) = H(ng) + 1;
          end;
     end;
endfunction;


function [N] = Norm(I);
			N=255*(I-min(I))/max(I)-min(I);
			imshow(N);
endfunction;



