initial commit

Assignment4_211/assignment4_3.m

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+clear; close all; clc;
+
+img = imread('pavian.png'); % Choose any picture you like here
+img = rgb2gray(img);
+
+%% Display image
+figure; subplot(131);
+imshow(img);
+title('Ausgangsbild');
+
+%% FFT
+fft2d = fft2(img);
+
+% Display the FFT image.
+subplot(132);
+imshow(log(fftshift(abs(fft2d))), []);
+title('2D-FFT');
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%
+
+% Approach: We want to remove the low frequencies (high pass filter) to
+% keep the areas of the image where the lightness changes relative to
+% nearby pixels
+
+% Shift FFT so low frequencies are in the center
+F = fftshift(fft2d);
+
+% Get image size
+[M, N] = size(F);
+
+% Radius of how much to remove
+r = 25;
+
+% We cut out the center of the fft low frequencies
+H = ones(M, N);
+H(M/2-r:M/2+r, N/2-r:N/2+r) = 0;
+
+% Apply filter
+F_filtered = F .* H;
+
+% Shift back
+fft2d = ifftshift(F_filtered);
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%% IFFT to obtain filtered image
+img_filtered = ifft2(fft2d);
+subplot(133);
+imshow(real(img_filtered), []);
+title('Gefiltertes Ausgangssignal');