Prashant Kumar answered . 2024-04-26 12:49:19

I understand that you want to take 7 patches of size 127X127 from the original image and make 3 of them lighter by adding 100 to there pixel values and 4 of them darker by subtracting 100 from there pixel values. You are not able to see any change in the image ‘A’ as you didn’t make any changes on it, rather stored the changed pixel values in ‘piece’. You can try this modified code.

clc;
A=imread('C:\Users\hp\Desktop\matlab\pictures\lenna.png');%sample image
rnd_x = randperm(size(A,1)-128,7);%choose 7 random unique points on x-axis
rnd_y = randperm(size(A,2)-128,7);%choose 7 random unique points on y-axis
image(A)
for ii = 1:4
    for jj = 5:7
        piece{jj} = A((rnd_x(jj):(rnd_x(jj)+127)),(rnd_y(jj):(rnd_y(jj)+127)),1:3)+100;
        A((rnd_x(jj):(rnd_x(jj)+127)),(rnd_y(jj):(rnd_y(jj)+127)),1:3)= piece{jj}; % add the changed pixel values to the original image A
        figure(jj)
        a=imadjust(jj);        
        imshow(piece{jj});
    end
    piece{ii} = A((rnd_x(ii):(rnd_x(ii)+127)),(rnd_y(ii):(rnd_y(ii)+127)),1:3)-100;%Convert chosen numbers to image pieces
    A((rnd_x(ii):(rnd_x(ii)+127)),(rnd_y(ii):(rnd_y(ii)+127)),1:3)= piece{ii}; % add the changed pixel values to the original image A
    figure(ii)
    b=imadjust(ii);    
    imshow(piece{ii});
end
imshow(A)

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