close all
clc
clear all

disp('Read the rgb image');
XX=imread('trees','JPEG'); % Provided by the instructor
figure(1), imshow(XX); title('24-bit color');
disp('the grayscale image and histogram');
Y=rgb2gray(XX); %RGB to grayscale conversion
figure(2), subplot(1, 2, 1);imshow(Y);
title('original');subplot(1, 2, 2);imhist(Y, 256);
disp('Equalization in grayscale domain');
Y=histeq(Y);
figure(3), subplot(1, 2, 1);imshow(Y);
title('EQ in grayscale-domain');subplot(1, 2, 2);imhist(Y, 256);
disp('Equalization of Y channel for RGB color image');
figure(4)
subplot(1, 2, 1);imshow(XX);
title('EQ in RGB color');
subplot(1, 2, 2);imhist(rgb2gray(XX), 256);
Z1=rgb2ntsc(XX); % Conversion from RGB to YIQ
Z1(:,:,1)=histeq(Z1(:,:,1)); %Equalizing Y channel
ZZ=ntsc2rgb(Z1); %Conversion from YIQ to RGB
figure(5)
subplot(1, 2, 1);imshow(ZZ);
title('EQ for Y channel for RGB color image');
subplot(1, 2, 2);imhist(im2uint8(rgb2gray(ZZ)), 256);
ZZZ=XX;
ZZZ(:,:,1)=histeq(ZZZ(:,:,1)); %Equalizing R channel
ZZZ(:,:,2)=histeq(ZZZ(:,:,2)); %Equalizing G channel
ZZZ(:,:,3)=histeq(ZZZ(:,:,3)); %Equalizing B channel
figure(6)
subplot(1, 2, 1);imshow(ZZZ);
title('EQ for RGB channels');
subplot(1, 2, 2);imhist(im2uint8(rgb2gray(ZZZ)), 256);
disp('Equalization in 8-bit indexed color');
[Xind, map]=rgb2ind(XX, 256); % RGB to 8-bit index image conversion
newmap=histeq(Xind, map);
figure(7)
subplot(1, 2, 1);imshow(Xind,newmap);
title('EQ in 8-bit indexed color');
subplot(1, 2, 2);imhist(ind2gray(Xind,newmap), 256);