Mat Lab Code for Modified Histogram Based Contrast Enhancement Using Unsharp masking Filter For Medical Images

clc;
clear;

img = (imread('mdb005.png'));

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

hist = imhist(img);    %histogrm

numOfPixels = size(img,1)*size(img,2);

iMean = mean(mean(img));    % mean of input image


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% histogram modification

g = zeros(256,1);

M = numOfPixels/256;

sai = 0.55;

for i = 1:256;
    g(i) = (hist(i)+(sai*M))/(1+sai);
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

prob = zeros(256,1);
cum = zeros(256,1);
output = zeros(256,1);

for i = 1:256;
    prob(i) = g(i)/numOfPixels;
end

sum = 0;
for i = 1:256;
    sum = sum+prob(i);
    cum(i) = sum;
end

for i = 1:256;
    output(i) = round(1+(256-1)*cum(i));
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

HIm=uint8(zeros(size(img,1),size(img,2)));
for i=1:size(img,1)
    for j=1:size(img,2)
            HIm(i,j)=output(img(i,j)+1);
    end
end


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Homomorphic Filtering after modification

img_fft = (log(double(HIm) + 1 ));  % log

img_fft = fft2(img_fft);     % fourior transform

size_img = size(img_fft);
lpf = [1 1 1;1 1 1;1 1 1]/9;

lpf_fft = fft2 ( lpf , size_img ( 1 ) , size_img ( 2 ) );  %% applying filter
result_fft = img_fft .* lpf_fft;

result_img = ( ifft2(result_fft) );   %% inverse fourior transform

result_img = exp (result_img);
result_img = uint8(real ( result_img ));

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

pMean = mean(mean(result_img));

result_img =  (iMean/pMean) .* result_img ;   %%normalize

subplot(3,2,1), imshow(img);
title('Original Image');

subplot(3,2,2), imshow(histeq(img));
title('HE Image');

subplot(3,2,3), imshow(adapthisteq(img));
title('CLAHE Image');

subplot(3,2,4), imshow(unsharpmasking(img));
title('USM Image');

subplot(3,2,5), imshow(HIm);
title('Image Before Normalization');

subplot(3,2,6), imshow(result_img);
title('MH-FIL');