function [F] = my_fourier(I)
    F = zeros(size(I));
    for k1 = 1:size(F,1)
        for k2 = 1:size(F,2)
            for n1 = 1:size(I,1)
                for n2 = 1:size(I,2)
                    F(k1,k2) = F(k1,k2) + I(n1,n2) * exp(-i*(2*pi/size(I,1))*(k1-1)*(n1-1)) * exp(-i*(2*pi/size(I,2))*(k2-1)*(n2-1));
                end
            end
        end
    end
end
