How to select every 54th image in the folder?

Suppose we have two folders A and B , both contain images.

Let folder A have 54 images:a1,a2,...,a54

folder B have 540 images: b1,b2,...,b540.

I want to select 10 images in B for each image in A, in the following way

for a1 select b1,b55, b109, b163, b217, b271, b325, b379, b433, b487

for a2 select b2,b56, b110, b164, b218, b272, b326, b380, b434, b488

.

.

.

for a54 select b54, b108, b162, b216, b270, b324, b378, b432, b486,b540

that is select every 54th entry.

Now I want to find uaci and npcr such that for each 'image a' I want to use 10 'image b', so that corresponding to each 'image a' I will get 10 uaci and npcr, and the function is attached.

Answer 1

[Awais Saeed]

I modified the code that I wrote for your last question as it might be easy to follow the same structure.

% path to the folder A that contains .png files
Folder_A_location = 'C:\Users\Awais\Documents\MATLAB\A';
% Get paths of <ALL> files in folder A
AFiles = fullfile(Folder_A_location, '*.png');
AFiles = dir(AFiles);
struct2table(AFiles)

% path to the folder B that contains .png files
Folder_B_location = 'C:\Users\Awais\Documents\MATLAB\B';
% Get paths of <ALL> files in folder B
BFiles = fullfile(Folder_B_location, '*.png');
BFiles = dir(BFiles);
struct2table(BFiles)

% a1, b1, b55, b109, b163, b217, b271, b325, b379, b433, b487 are in row # 1 of Acell
% a2, b2, b56, b110, b164, b218, b272, b326, b380, b434, b488 are in row # 2 of Acell
% and so on
for AfileNum = 1:1:length(AFiles)
    AfileName = AFiles(AfileNum).name;
    fprintf('Loaded file # %d, name = %s \n',AfileNum, AfileName)
    col = 1;
    % read image (Must provide full path)
    AFileLoaded = imread([Folder_A_location '\' AfileName]);
    Acell{AfileNum,col} = AFileLoaded;
    
    for BfileNum = AfileNum:54:length(BFiles)
        col = col + 1;
        BfileName = BFiles(BfileNum).name;
        fprintf('Loaded file # %d, name = %s \n',BfileNum, BfileName)
        % read image (Must provide full path)
        BFileLoaded = imread([Folder_B_location '\' BfileName]);
        Acell{AfileNum,col} = BFileLoaded;
    end
end
% Now all images are in Acell{} according to your selection criteria.
% Loop through Acell{} and perform your operations

I did not check the code as I do not have access to MATLAB right now. In case of any error, I hope you can find a solution. I used fprintf() to see what is being loaded for easy debugging. You can remove those as well.

[Awais Saeed]

1. I was just not providing the full path of image in imread(). I have updated the code.
2. You said there are two folders namely A and B. That is why I used C:\Users\Awais\Documents\MATLAB\A and C:\Users\Awais\Documents\MATLAB\B
3. Now to your question how to pick 1 image from folder A and then pick 10 images from folder B one by one? All images are in Acell cell array. Row # 1 has a1, b1, b55, b109, b163, b217, b271, b325, b379, b433, b487 in it. Same goes for remaining rows. Just loop through them as following:

for row = 1:1:size(Acell,1)
    A = Acell{row,1}; % to pick a1 in first iteration
    for col = 2:1:size(Acell,2)
        B = Acell{row,col};
        % find npcr value. Call it x
        npcr_result(row,col-1) = x
%         % find uaci value. Call it y
        uaci_result(row,col-1) = y
    end
end
% At the end, you will have 10 values for a1 in row # 1
% 10 values for a2 in row # 2 and so on

[Ammy]

Thank you very much.

Answer 2

[Jan]

A = 'D:\Your\A';
B = 'D:\Your\B';
AList = dir(fullfile(A, 'a*.jpg'));
BList = dir(fullfile(B, 'b*.jpg'));
nB    = numel(BList);

for iA = 1:numel(AList)
    imageA     = fullfile(A, AList(iA).name);
    indexB     = iA:54:nB;
    imageBList = fullfile(B, {BList(indexB).name});
    for iB = 1:imageBList
       imageB = imageBList{iB};
       ... 
    end
end

If you are sure that all file names a1 to a54 and b1 to b540 are existing, you can create the file names automatically also:

A = 'D:\Your\A';
B = 'D:\Your\B';
for iA = 1:54
    imageA = fullfile(A, sprintf('a%d.jpg', iA));
    for iB = iA:54:540
       imageB = fullfile(B, sprintf('b%d.jpg', iB));
       ... process imageA and imageB now
    end
end