function F = gauss(size)
% utilisation: M=gauss(size);
% cree un filtre gaussien de diametre size (4 x ecart-type)
% size doit etre impair
F=zeros(size,size);
X=[1:size]-(1+size)/2;
et=size/4;
for i=X
   for j=X
     F(i+(1+size)/2,j+(1+size)/2) = exp(-(i*i+j*j)/(2*et*et));
   end;
end;
F=F/sum(sum(F));
