making the number of images the same

Hello

I have a folder with subfolders, in subfolders, there are images, but the number of images aren't the same,

by the following code, I read them, but for extracting feature, I have a problem, I have to make the number of images the same.

Please help me.

imw=81;
imh=71;
Mainfolderlist=dir('E:\cropped\*');
totvideofeat=[];

for k=1:length(Mainfolderlist)
    if(strcmp(Mainfolderlist(k).name,'.')||strcmp(Mainfolderlist(k).name,'..')),continue; end
    subfolderlist=dir(strcat(Mainfolderlist(k).folder,'\',Mainfolderlist(k).name,'\*'));
    for l=1:length(subfolderlist)
        if(strcmp(subfolderlist(l).name,'.')||strcmp(subfolderlist(l).name,'..')),continue; end
        patht=strcat(subfolderlist(l).folder,'\',subfolderlist(l).name,'\*.jpg');
        pathi=dir(patht);   
        videofeat=CalcVidFeat(pathi,imw, imh,param,opticFlow);
        totvideofeat=[totvideofeat,videofeat];
        
    end
    
end

Answer 1

[Deepak]

Hi @azam.e,

From my understanding, you have subfolders within a folder, and those subfolders contain images for feature extraction. But the number of images in subfolders is not the same, and feature extraction requires the same number of images.

To make the number of images equal in each subfolder, we can use truncation and padding techniques. We can initially set “fixedNumberOfImages”, as the number of images required in each subfolder. Then, we can truncate the extra images in a subfolder, and we can also pad (replicate) the images if a subfolder contains a smaller number of images than required.

To truncate the number of images, we can use array indexing and set the “pathi” array size to “fixedNumberOfImages”. Also, to pad the images, we can use “repmat” function in MATLAB to repeat the array elements until the required array size is reached.

Here is the complete MATLAB code that addresses this task:

imw = 81; 
imh = 71; 
fixedNumImages = 10; % Set the desired number of images per subfolder 
Mainfolderlist = dir('E:\cropped\*'); 
totvideofeat = []; 

for k = 1:length(Mainfolderlist) 
    if strcmp(Mainfolderlist(k).name, '.') || strcmp(Mainfolderlist(k).name, '..') 
        continue; 
    end 
    subfolderlist = dir(fullfile(Mainfolderlist(k).folder, Mainfolderlist(k).name, '*')); 
    for l = 1:length(subfolderlist) 
        if strcmp(subfolderlist(l).name, '.') || strcmp(subfolderlist(l).name, '..') 
            continue; 
        end 
        patht = fullfile(subfolderlist(l).folder, subfolderlist(l).name, '*.jpg'); 
        pathi = dir(patht); 
        
        % Determine the number of images to process 
        numImages = length(pathi); 
        
        if numImages >= fixedNumImages 
            % Truncate the list to the desired number of images 
            pathi = pathi(1:fixedNumImages); 
        else 
            % Pad the list by repeating images 
            repeatFactor = ceil(fixedNumImages / numImages); 
            pathi = repmat(pathi, repeatFactor, 1); 
            pathi = pathi(1:fixedNumImages); % Ensure we have exactly fixedNumImages 
        end 
        
        videofeat = CalcVidFeat(pathi, imw, imh, param, opticFlow); 
        totvideofeat = [totvideofeat, videofeat]; 
    end 
end 

Attaching the documentation of “array indexing” and “repmat” in MATLAB for reference:

https://www.mathworks.com/help/matlab/math/array-indexing.html

https://www.mathworks.com/help/matlab/ref/repmat.html

I trust this will address the problem.