How to divide images from folder into 4x4 blocks
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Petrus van Aswegen
on 5 May 2021
Commented: Petrus van Aswegen
on 5 May 2021
I want to divide all images in a folder into 4x4 blocks and then store the RGB information in a zeros matrix. A sample of what the images look like is attached. Does anyone know how to divide into these blocks and then store the information in the matrix.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/607780/image.png)
3 Comments
Turlough Hughes
on 5 May 2021
Edited: Turlough Hughes
on 5 May 2021
Also, consider the blockproc function. This might be the way to go depending on what it is you're trying to do.
Accepted Answer
Turlough Hughes
on 5 May 2021
Hi Petrus, the mat2cell approach that Jonas pointed out can be done more generally as follows. Note, this handles the scenario where image dimensions are not a factor of the corresponding block dimensions (the remainder rows or columns are ommited)
1. Parameters
blockHeight = 4;
blockWidth = 4;
folderName = 'C://...'; % folder containing images
2. Directory. These three lines can be used by others to replicate the demo. Once you modify folderName you can replace the following three lines with the fourth one.
[fils(1:6).folder] = deal('');
fnames = cellfun(@(x) sprintf('office_%s.jpg',x),{'1','2','3','4','5','6'},'uni',false);
[fils.name] = fnames{:};
%fils = dir(fullfile(folderName,'*.PNG')); < Replace the above with this line
3. Load an initial image to get some metadata:
I0 = imread(fullfile(fils(1).folder,fils(1).name));
N1 = blockHeight*ones(floor(size(I0,1)/blockHeight),1);
N2 = blockWidth*ones(floor(size(I0,2)/blockWidth),1);
4. Loop through your directory:
L = cell(numel(fils),1);
for ii = 1:numel(fils)
I = imread(fullfile(fils(ii).folder,fils(ii).name));
b = mat2cell(I(1:blockHeight*numel(N1),1:blockWidth*numel(N2),:),N1,N2,3);
L{ii} = cat(4,b{:}); % alternatively L{ii} = b;
end
L
The result, L, is then a 6 by 1 cell array of matrices where each cell corresponds to an image. The matrix dimensions (4x4x3x3750) correspond to the block height, block width, RGB, and a linear index for the block.
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