Function returns different value when applied on multiple images using a loop

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Unqua Laraib 2020-7-1

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https://ww2.mathworks.cn/matlabcentral/answers/557920-function-returns-different-value-when-applied-on-multiple-images-using-a-loop

评论： Walter Roberson 2020-7-2

I have total 196 (.jpg) images in a folder whose LBP features i want to extract. Also i want to save the feature vectors of all 196 images in one matrix/array.

I have written a code for LBP to be applied on images, when i apply the code on a single images it returns the correct 1x256 size feature vector with the right values(which i need). But when the same code is applied on multiple images in a folder via loop it returns different values...i dont uderstand how come the values are different? Much help is needed. Thankx in advance

clear all;  
close all; 
clc;
location = 'E:\img_folder\*.jpg'; %  folder in which 196 images exists
ds = imageDatastore(location); % datastore
Final =[]; % the final marix in which i wish to append feature vector of all images in the folder
while hasdata(ds) %using while to loop through all images
    
    I2=read(ds);   % read image from datastore
    
    w=size(I2,1);
    h=size(I2,2);
    scale = 2.^[7 6 5; 0 -inf 4; 1 2 3];
    
    %LBP code    
    for i=2:w-1
        for j=2:h-1          
            
            J0=I2(i,j);
            I3(i-1,j-1)=I2(i-1,j-1)>J0;
            I3(i-1,j)=I2(i-1,j)>J0;
            I3(i-1,j+1)=I2(i-1,j+1)>J0; 
            I3(i,j+1)=I2(i,j+1)>J0;
            I3(i+1,j+1)=I2(i+1,j+1)>J0; 
            I3(i+1,j)=I2(i+1,j)>J0; 
            I3(i+1,j-1)=I2(i+1,j-1)>J0; 
            I3(i,j-1)=I2(i,j-1)>J0;
            LBP(i,j)=I3(i-1,j-1)*2^7+I3(i-1,j)*2^6+I3(i-1,j+1)*2^5+I3(i,j+1)*2^4+I3(i+1,j+1)*2^3+I3(i+1,j)*2^2+I3(i+1,j-1)*2^1+I3(i,j-1)*2^0;
        end
    end
    [pixelCounts, GLs] = imhist(uint8(LBP));
    Final=[Final;pixelCounts];
end
I know there is nothing wrong with the LBP code but something with concatenation in the Final[] matrix/array.

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Unqua Laraib 2020-7-2

Matlab is reading images like this :kang0 ,kang1, kang10,kang100,kang101 and so on

Please tell me if there is a way i can make Matlab read in the right order like kang0,kang1,kang2,kang3.....so on

something like this in a loop: kang[i]

and "i" should change/increment in each order.

Walter Roberson 2020-7-2

There is nothing you can do directly to have it process the files in numeric order. datastores retrieve the file names from the directories in whatever order the operating system happens to present them, and there is no "order" option.

However, instead of passing the datastore a pattern with wildcards, you can find the file names, and use a sort routine such as https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort and then pass the cell array of file names to the imagedatastore()

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