extract matrix from matrix

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Jitesh Bhanushali 2014-4-11

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https://ww2.mathworks.cn/matlabcentral/answers/125418-extract-matrix-from-matrix

评论： the cyclist 2014-4-25

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

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the cyclist 2014-4-12

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

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the cyclist 2014-4-11

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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