How to change one pixel only in plain image?

How can I change one pixel in an image?

I need this to calculation NPCR and UACI between to cipher images whose plain images have only a one-pixel difference. hence, ineed original image and original image with edit value of on pixel only to encrypt them.

Answer 1

[Kevin Holly]

I = imread('peppers.png');

imshow(I)

size(I)

ans = 1×3

384 512 3

I(45,45,1) = 255; % red
I(45,45,2) = 255; % green
I(45,45,3) = 255; % blue
imshow(I)

grayscale_I = rgb2gray(I);


imshow(grayscale_I)

size(grayscale_I)

ans = 1×2

384 512

I(45,45) = 255;
imshow(I)