extract matrix from matrix

sir i have image of size 256*256 and i want to extract 5*5 matrix from every 8*8 block of 256*256 image what is code for this...also i want to add zeros to all 5*5 blocks and make 5*5 to 8*8 matrix of the 256*256 image ..what is code for this

[the cyclist]

For your second question, how are the 5x5 blocks stored, specifically?

Answer 1

[the cyclist]

Here is a very straightforward way to do this:

% Put in some pretend data
bigMatrix = rand(256);

% The algorithm
for ni=1:8:256
for nj = 1:8:256
    i_idx = (ni-1)/8+1; 
    j_idx = (nj-1)/8+1; 
    smallMatrices{i_idx,j_idx} = bigMatrix(ni:ni+7,nj:nj+7);
    smallMatrices{i_idx,j_idx}(:,6:8) = 0;
    smallMatrices{i_idx,j_idx}(6:8,:) = 0;
end
end

[Jitesh Bhanushali]

sir i want 2 different code for that

[the cyclist]

If you remove the lines where I set the rows/columns to zero, then it solves your first issue.

[Jitesh Bhanushali]

sir how to solve second issue

[the cyclist]

I can't help you solve the second issue until you respond to the comment I made (just under your question). How are the 5x5 blocks stored?