Image Processing Basics - Digital Signal Processing: Fundamentals and Applications - page 721

Program 14.2. Examples of Gaussian filtering, media filtering, and Laplacian of Gaussian filtering.

close all;clear all; clc;
X ¼ imread( ' cruise ' , ' jpeg ' ); % Provided by the instructor

Y ¼ rgb2gray(X); % Convert the RGB image to the grayscale image

I ¼ im2double(Y); % Get the intensity image

image1_g ¼ imnoise(I, ' gaussian ' ); % Add random noise to the intensity image

ng ¼ mat2gray(image1_g); % Adjust the range

ng ¼ im2uint8(ng); % 8-bit corrupted image

% Linear filtering
K_size ¼ 5; % Kernel size ¼ 5 5
sigma ¼ 0.8; % sigma (the bigger, the smoother the image)
h ¼ fspecial( ' gaussian ' ,K_size,sigma); % Determine Gaussian filter coefficients
% This command will construct a Gaussian filter
% of size 5 5 with a main lobe width of 0.8.
image1_out ¼ filter2(h,image1_g); % Perform filtering
image1_out ¼ mat2gray(image1_out); % Adjust the range
image1_out ¼ im2uint8(image1_out); % Get the 8-bit image
subplot(1,2,1); imshow(ng),title( ' Noisy image ' );
subplot(1,2,2); imshow(image1_out);
title( ' 5 5 Gaussian kernel ' );
% Median filtering
image1_s

¼ imnoise(I, salt & pepper ); % Add salt and pepper noise to the image

' ' “ ”

mn ¼ mat2gray(image1_s); % Adjust the range

mn ¼ im2uint8(mn); % Get the 8-bit image

K_size 3; % Kernel size

image1_m ¼ medfilt2(image1_s,[K_size, K_size]); % Perform median filtering
image1_m ¼ mat2gray(image1_m);

¼

% Adjust the range

image1_m ¼ im2uint8(image1_m); % Get the 8-bit image

figure, subplot(1,2,1);imshow(mn)
title( ' Median noisy ' );
subplot(1,2,2);imshow(image1_m);
title( ' 3 3 median kernel ' );
% Laplacian of Gaussian filtering
K_size ¼ 5; % Kernel size

sigma ¼ 0.9; % Sigma parameter

h ¼ fspecial( ' log ' ,K_size,alpha); % Determine the Laplacian of Gaussian %filter

kernel
image1_out ¼ filter2(h,I); % Perform filtering

image1_out ¼ mat2gray(image1_out); % Adjust the range

image1_out ¼ im2uint8(image1_out); % Get the 8-bit image

figure,subplot(1,2,1); imshow(Y)
title( ' Original ' );
subplot(1,2,2); imshow(image1_out);

title( Laplacian lter 5 5 kernel );

' '