select random pixels

I have an image , I have to select random pixels and replace with some values I have. How can I do that?

Answer 1

[Titus Edelhofer]

Hi,

randperm should help you, here some (non tested) example code:

% let A be the image (either NxM or NxMx3):
% number of pixels to be replaced:
k = 42;
% the size:
s = size(A);
if length(s)==3
   %RGB
   A = reshape(A, s(1)*s(2), 3);
else
   A = A(:);
end
% the random pixels:
idx = randperm(size(A,1));
A(idx,:) = 0; % black or other values
% and reshape back
A = reshape(A, s);

Titus