Image matrix cell color

I have imported an image using imread - which creates a matrix of the image. The size of such a matrix is n x m x p. I think p refers to the colour information of each cell. I am using imshow to display these matrices.

Parts of the image, that are white, have the value of 255. How can I change the colour of a specific cell to a colour of my choice? I have tried stuff like X(1,10) = 230, but that doesnt seem to do anything. Could someone please help? Thanks,

Answer 1

[DGM]

Let's say you just want to change one pixel

A = imread('peppers.png');

newcolor = [230 50 185];

B = A;
B(50,50,:) = newcolor;

imshow(B); hold on
plot(50,50,'wo','markersize',50) % highlight the pixel that changed

Or say you want to change a rectangular block of pixels

B = A;
B(50:100,50:100,:) = repmat(permute(newcolor,[1 3 2]),[51 51]);
clf; % for web view
imshow(B); 

Or say you want to change an arbitrary region of the image:

mask = uint8(rgb2gray(A) > 220);
colorpict = uint8(repmat(permute(newcolor,[1 3 2]),size(mask)));
B = A.*(1-mask) + colorpict.*mask;
clf; % for web view
imshow(B);

There are plenty of other ways

[Wouter Theron]

Exactly what I needed. Thank you so much!