get distnct blocks contained in a given matrix.

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MatlabEnthusiast
MatlabEnthusiast 2021-11-23
评论： MatlabEnthusiast 2021-11-24
Hello. Lets say an image of size [M N] to blocks of size [i j] each. using the following piece of code:
A = im2col(im,[i j],'distinct');
% ....
% ....
% ....
% do some more operations on A
% derive submatrix B of size [m n] from A.
% QUESTION
% How can I retrieve the distnct blocks of size (i, j) contained in B
% and store them say in a different matrix.
% Thank you very much.
After a series of more operations, I derive a submatrix, say B of size [m n] from A.
My question is. How can I find how many blocks of size (i, j) are in B. Also how can I store these blocks in a different array? Thank you very much.

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Walter Roberson
Walter Roberson 2021-11-23
In any one direction, if you need distinct blocks of size P and the available length along the dimension is Q, then the number of ways you can position the block along that dimension is (Q-P+1) . For example blocks of length 3 in a vector of length 5, [a b c d e f] can be [a b c], [b c d], [d e f] -- three different blocks, and (5-3+1) = 3 .
Now you have the same calculation along the other dimension.
Finally, you multiply the values for all of the dimensions.
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Walter Roberson
Walter Roberson 2021-11-24
When you pass an array into num2cell, and you pass in the optional argument 1 then the output will be a cell array in which each column of the original matrix is an individual cell array entry.
MatlabEnthusiast
MatlabEnthusiast 2021-11-24
alright Walter. Finally, So how is this for a crude extraction of block starting at (1,1). If its right, how best can I generalize this to get say, the block at (r, c)?
b1_crude=[separated{1}(1:8) separated{2}(1:8) separated{3}(1:8) separated{4}(1:8) separated{5}(1:8) separated{6}(1:8) separated{7}(1:8) separated{8}(1:8)];

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