%   Call: tdft_8x8.m.m
%   Demo code for calculating the 8x8-point DFT by
%   the tensor transform: 12 8-point DFTs are used
%
%   Dr. Artyom M. Grigoryan,         11/12/1997

        N=8;
        f=[ 1  2  1  3  1  2  1  3
            2  4  1  1  2  3  2  1
            1  3  2  2  1  1  3  2
            1  2  1  1  3  1  2  1
            2  4  1  2  1  2  3  2
            3  2  2  3  2  1  1  3
            1  2  3  4  2  1  3  2
            2  3  1  2  1  3  1  2];
        F2D=fft2(f);                

        % 2-D DFT by the tensor transform
        FT=zeros(N);
        s=1;
        for p=0:N-1
            Image_signal=zeros(1,N); 
            Image_signal=ft_pst(f,p,s);      
            TDFFT_signal=fft(Image_signal);
            T_ps=cyclic_group(p,s,N)+1;
            for k=1:N
                p1=T_ps(k,1);
                s1=T_ps(k,2);
                FT(s1,p1)=TDFFT_signal(k);
            end;                    
        end;
        p=1; L=2;
        for s=0:L:N-1
            Image_signal=zeros(1,N); 
            Image_signal=ft_pst(f,p,s);      
            TDFFT_signal=fft(Image_signal);
            T_ps=cyclic_group(p,s,N)+1;
            for k=1:N
                p1=T_ps(k,1);
                s1=T_ps(k,2);
                FT(s1,p1)=TDFFT_signal(k);
            end;                    
        end;
        % to check if the 2-D DFT has been calculated correctly:
        Inv_image=real(ifft2(FT));
        %Inv_image=Inv_image.*(Inv_image>=0);
        Inv_image=round(Inv_image);        
        fprintf('    %2d %2d %2d %2d %2d %2d %2d %2d \n',Inv_image');  
        %  1  2  1  3  1  2  1  3 
        %  2  4  1  1  2  3  2  1 
        %  1  3  2  2  1  1  3  2 
        %  1  2  1  1  3  1  2  1 
        %  2  4  1  2  1  2  3  2 
        %  3  2  2  3  2  1  1  3 
        %  1  2  3  4  2  1  3  2 
        %  2  3  1  2  1  3  1  2