Frequency Domain Filtering

This program demonstrate the frequency domain filtering techniques like lowpass, high pass, laplacian filtering etc

Contents

• Start
• Read the Image
• Take the fourier transform
• Filter Design
• Pass the image through filter
• Display the result

Start

clear all;
close all;
clc;

Read the Image

%x1 = imread('broken.jpg');
%x1 = double(rgb2gray(x1))/255;
x1 = imread('cameraman.tif');
%x1 = imread('coins.png');
x1 = double(x1)/255;
%x1 = ones(9,9);

Take the fourier transform

F = fft2(x1);

Filter Design

[x y] = size(F);
d0 = 50;
H = ones(size(F));
for i = 1:x-1
for j =1:y-1
dist = ((i-x/2)^2 + (j-y/2)^2)^.5;
if dist > d0
H(i,j) = 0;
end
end
end

Pass the image through filter

F = fftshift(F);
Fhat = H.*F;
Fhat = fftshift(Fhat);
r = ifft2(Fhat);
r = abs(r/max(max(r)));

Display the result

Original Image

imshow(x1);

Filtered image

figure;imshow(r);