How do we extract an m*n matrix from a larger p*q matrix?

I have an image which is divided into 8*8 blocks grid. I am finding DCT of each block in this image using blocproc which is followed by idct. This gives me idct of the entire image(a matrix of 512*512 is obtained). How do I extract dct of one block(i.e. dct of a single block out of 512*512 blocks) to obtain a 8*8 matrix out of 512*512 one.

[Rik]

With block=total(1:8,1:8);?

[Chandvi Arora]

I am able to do what I want with this. Thanks a lot.

Answer 1

[KSSV]

This question is asked multiple times:

https://in.mathworks.com/matlabcentral/answers/328673-how-to-divide-rgb-image-into-blocks-using-for-loop-and-find-the-rgb-value-for-each-block

https://in.mathworks.com/matlabcentral/answers/89757-how-to-divide-256x256-matrix-into-sixteen-16x16-blocks

http://in.mathworks.com/matlabcentral/fileexchange/35085-mat2tiles-inarray-varargin-

[Chandvi Arora]

In the last link, how to determine the value of [20x6x3 double]? I need the exact value.