% Construct Figure 2.9b from Digital Signal and Image Processing
% Tamal Bose
% Plot the 2-D DFT of 3 x 3 mean filter with quadrant swaps
w1=[-pi:2*pi/200:pi-(2*pi/200)];
w2=[-pi:2*pi/200:pi-(2*pi/200)];
x = [ones(3)/9];
x_mag_spectrum = abs(fftshift(fft2(x,200,200)));
surf(w1, w2, x_mag_spectrum)
colormap hsv
colorbar
xlabel('\omega1');
ylabel('\omega2');
zlabel('Magnitude');
title('Shifted Plot of 3 x 3 Mean Filter Frequency Spectrum');