Divide a matrix into submatrices in MATLAB

Question

I have an RGB image of size 412x550. I want to divide it into sub matrices of size 2x2. I have tried using mat2cell function but it is

Answer 1

In general, you can use the following code to divide the image into blocks (for compression process or whatever)

    A=imread('image.bmp'); % i assume 8-bit gray scale image
    [m,n,k]=size(A); % and m=n with 1 channel k=1
    ImageSize=m*n;
    BlockD=2; % i assume 2x2 block
    BlockSize=BlockD*BlockD;
    NoOfBlock=ImageSize/BlockSize;
    SubB=zeros(BlockD,BlockD,NoOfBlock); %arrays of blocks.
    B=double(A); important to convert uint8 to double when dialing with image.
    % thats what ru asking for.
    k=1;
    for i=1:BlockD:m
    for j=1:BlockD:n
        SubB(:,:,k)=B(i:i+BlockD-1,j:j+BlockD-1); k=k+1;
    end
    end
    %compare between first submatrix A with first block.. its the same elements.
    B(1:2,1:2)
    SubB(:,:,1)

Answer 2

You probably got the syntax a bit off. The correct syntax for your situation would be

>> A = rand(412,550);
>> B = mat2cell(A, 2*ones(size(A,1)/2,1), 2*ones(size(A,2)/2,1))

ans = 
    [2x2 double]    [2x2 double]    ... 
    [2x2 double]    [2x2 double]    ...
    ...

Answer 3

You should use the function im2col. It is exactly what you need.

A = rand(412,550);
B = im2col(A,[2 2]);

The doc is there:

http://www.mathworks.fr/help/images/ref/im2col.html;jsessionid=4d24325613716d84d4635b4fc636