function im_out=equalizza(im,L)

[m,n]=size(im); N=m*n;
%ist=istogramma(im,L);
ist=zeros(L,1); for i=1:L, ist(i)=sum(sum(im==i-1)); end;
r=[0.0:1/(L-1):1.0]'; s=cumsum(ist)/N;
ss=[0:L-1]'; ss=round(ss+(s-r)*(L-1));

im_vett=reshape(im,m*n,1);
im_out=uint8(reshape(ss(im_vett),m,n));