How to read images sequentially from a folder?

Question

Zara Khan 2022-7-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1753580-how-to-read-images-sequentially-from-a-folder

编辑： Stephen23 2022-7-6

sourcefolder = 'E:\images';
filepattern = fullfile(sourcefolder, '*.png');
outputfolder = 'E:\images2';
srcFiles = dir(filepattern);
numImages = length(srcFiles);
for k = 1 : numImages
        
    inputfilename = fullfile(sourcefolder, srcFiles(k).name);
    outputfilename = fullfile(outputfolder, sprintf('histo_%d.png',k));
    .....
    ....
    ....
end

My folder containing 1400 images. Whenever I am reading images using the above code and after performing any image processing its not happening sequentially. How can read images by one by one maintaing the sequence and can write to them by maintaining the same order.

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Chunru 2022-7-5

you need to sort the srcFiles first according to your need.

Zara Khan 2022-7-5

how to do that

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Answer 1

Stephen23 2022-7-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1753580-how-to-read-images-sequentially-from-a-folder#answer_1000330

编辑：Stephen23 2022-7-6

在 MATLAB Online 中打开

You can download the file NATSORTFILES by clicking the big blue download button here:

https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

then unzip the file onto the MATLAB search path (e.g. into the current directory), and then use it like this:

srcFiles = dir(filepattern);
srcFiles = natsortfiles(srcFiles);

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Zara Khan 2022-7-6

It worked. Thanks

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Answer 2

Pooja Kumari 2022-7-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1753580-how-to-read-images-sequentially-from-a-folder#answer_1000375

编辑：Pooja Kumari 2022-7-5

在 MATLAB Online 中打开

Dear Zara Khan,

It is my understanding that you want to access the images present in the folder sequentially and after performing some operations, you want to store the output image in ‘output filename’.

But the issue you were facing is that when you are reading images using the provided code and after getting the input file name and performing some image processing, you were not getting the output sequentially is because the files stored in input file name is not sequential.

You can refer to the updated code given below:

sourcefolder = 'E:\images'; %path of your source folder 
filepattern = (fullfile(sourcefolder, '*.png'));
srcFiles = dir(filepattern);
numImages = length(srcFiles);
outputfolder = 'E:\images2';
for i= 1: numel(srcFiles)
    I =(imread(strcat(sourcefolder,'/',srcFiles(i).name)));
    outputfilename = fullfile(outputfolder, sprintf('histo_%d.png',i));
    .....
        ....
        ...
end

Please find attached a reference code for the above issue you were facing:

% I have 50 images named numerically '15_1_s', '15_2_s', ... '15_50_s' but
% the order in which these files are stored is shown in the image below: 
path = '/MATLAB Drive/CV_Assignment2/dd/dd';
folder = (path);
files = dir(fullfile(folder,'*.jpg'));
nfiles = length((files));
mkdir(['Outputfolder',sprintf('%d',outputfolder)]);  % similar to outputfolder.
for i= 1: numel(files)
    I =(imread(strcat(path,'/',files(i).name)));
    imwrite(imgx,strcat(path_output,'/',files(i).name));
    %output will be stored sequentially . 
end

For more information on how to sort files stored in a directory , you can refer to the below link:

https://in.mathworks.com/matlabcentral/answers/167001-how-to-sort-file-when-reading-them-with-dir

You can refer to this file, if you want to sort the input files naturally:

https://in.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort?requestedDomain=

Sincerely,

Pooja Kumari

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Zara Khan 2022-7-6

Thank you madam for very nice explanation of my problem. Thanks once again for the response. I have used the natsortfiles in this case and its working well till now. I will also give a try of your answer also. Thanks.

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Answer 3

Chunru 2022-7-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1753580-how-to-read-images-sequentially-from-a-folder#answer_1000240

编辑：Chunru 2022-7-5

在 MATLAB Online 中打开

% create some files
system('touch a.png');
system('touch c.txt');
pause(1)  % make sure b is newer in datenum
system('touch b.txt');
pause(.5)
% get the files
f = dir('*.*');
{f.name}
ans = 1×5 cell array
    {'.'}    {'..'}    {'a.png'}    {'b.txt'}    {'c.txt'}
% sort according to name
[~, idx] = sort({f.name})
idx = 1×5
     1     2     3     4     5
fname = {f(idx).name}
fname = 1×5 cell array
    {'.'}    {'..'}    {'a.png'}    {'b.txt'}    {'c.txt'}
% sort according to datetime
[~, idx] = sort([f.datenum])
idx = 1×5
     2     3     5     1     4
fname = {f(idx).name}
fname = 1×5 cell array
    {'..'}    {'a.png'}    {'c.txt'}    {'.'}    {'b.txt'}

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Zara Khan 2022-7-5

编辑：Zara Khan 2022-7-5

Sorted by names . Like they are img1, img2,......img1400. I have tried with natsortfiles also. But the function is telling undefined

Walter Roberson 2022-7-5

You need to use the Add-On Explorer to install natsortfiles .

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How to read images sequentially from a folder?

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