MATLAB: How to traverse an image in 2×2 block wise wayand then check suitable conditions

Question

i am actually working for coloring a grayscale image.

Answer 1

Img = rand(640, 480);
Img = reshape(X, 2, 320, 2, 240);
B   = permute(Img, [1, 3, 2, 4]);
for i = 1:320
  for j = 1:240
    aBlock = B(:, :, i, j);
    ...
  end
end
Img2 = ipermute(Block, [1, 3, 2, 4]);
Img2 = reshape(Img2, 640, 480);