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Image matrix cell color

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Wouter Theron
Wouter Theron on 10 Oct 2021
Commented: Wouter Theron on 10 Oct 2021
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,

Accepted Answer

DGM
DGM on 10 Oct 2021
Edited: DGM on 10 Oct 2021
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
  1 Comment
Wouter Theron
Wouter Theron on 10 Oct 2021
Exactly what I needed. Thank you so much!

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