histo_equalization.m

clc; clear all; close all;
a=imread('KalpanaCrew.jpg');
n=size(a,1)*size(a,2);
r=size(a,1);
c=size(a,2); 
ah=uint8(zeros(r,c));
f=zeros(256,1);
pdf=zeros(256,1);
cdf=zeros(256,1);
cum=zeros(256,1);
out=zeros(256,1);
 
for i=1:r%accessing image rows
    for j=1:c%accessing image columns
        value=a(i,j);
        f(value+1)=f(value+1)+1;
        pdf(value+1)=f(value+1)/n;
    end
end
 
sum=0; L=255;
 
for i=1:size(pdf)
   sum=sum+f(i);
   cum(i)=sum;
   cdf(i)=cum(i)/n;
   out(i)=round(cdf(i)*L);
end
 
for i=1:r
    for j=1:c
            ah(i,j)=out(a(i,j)+1);
    end
end

figure,imshow(a);
title('Original Image');
figure,imshow(ah);
title('Histogram Equalized Image (Implementation)');
figure,imshow(histeq(a));
title('Histogram Equalized Image (Inbuilt)');

figure,
subplot(311);imhist(a);title('Histogram of Original Image');

subplot(312);imhist(ah);title('Histogram of Implemented Image');

subplot(313);imhist(histeq(a));title('Histogram of Inbuilt Function Image');