How to modify the images, were read by "dir" function?

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판석 2024-9-16，14:55

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评论： Stephen23 2024-9-20，5:29

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Hello, So nice guys.

Can you help me?

I did print out many images like this below.

--------------------------------------

path='C:\'
list=dir(path)
name={list.name}
imagelist=name(3:end)
montage(imagelist)

-------------------------------------

I want to modify (example: imrotate, im2gray etc..) the images before I print out the images (montage);

Also, I want to save these images using function imwrite.

But, I couldn't,,

So, What can I do for this?

Thank you

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Stephen23 2024-9-20，5:29

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As an aside, note that

imagelist=name(3:end)

is a buggy attempt to remove the dot directory names:

https://www.mathworks.com/matlabcentral/answers/166629-is-there-any-way-to-list-all-folders-only-in-the-level-directly-below-a-selected-directory

https://www.mathworks.com/matlabcentral/answers/13978-list-of-files-sorting#answer_19278

https://www.mathworks.com/matlabcentral/answers/40949-omitting-pointers-when-listing-folder-contents#answer_50568

https://www.mathworks.com/matlabcentral/answers/166629-is-there-any-way-to-list-all-folders-only-in-the-level-directly-below-a-selected-directory#comment_510206

https://www.mathworks.com/matlabcentral/answers/484430-using-struct-dir-selpath-what-do-and-mean-as-struct-name#answer_395754

https://www.mathworks.com/matlabcentral/answers/1699230-folder-listing-with-dir-on-mac#answer_945260

As Walter Roberson wrote: "That code is wrong on every operating system that MATLAB has ever run on".

The recommended approach is to specify a non-empty DIR search name, or use e.g. ISMEMBER, SETDIFF, or similar:

https://www.mathworks.com/matlabcentral/answers/166629-is-there-any-way-to-list-all-folders-only-in-the-level-directly-below-a-selected-directory#comment_624696

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Answer 1

dpb 2024-9-16，15:21

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montage returns only an montage object; not the individual images. Review the information at <Image Sequences and Batch Processing> and select from the various options outlined the best that matches your needed workflow to process each image.

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Answer 2

Angelo Yeo 2024-9-20，0:45

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编辑：Angelo Yeo 2024-9-20，4:59

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Neither imrotate nor im2gray support sequence image processing so I believe it would be good to use for loops in this case.

imds = imageDatastore(fullfile(matlabroot,"toolbox","images","imdata","AT3*.tif"));

figure; montage(imds); title('original image set')

N = length(imds.Files);

tempCell = cell(N, 1);

for i =1:N

I = readimage(imds,i); % fixed from "N" to "i". Thanks to DGM's comment.

I = imrotate(I, 90);

I = im2gray(I);

tempCell{i} = I;

end

figure; montage(tempCell); title('processed image set')

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DGM 2024-9-20，3:20

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If the goal is to save the composite image, use imtile() instead of montage().

imds = imageDatastore(fullfile(matlabroot,"toolbox","images","imdata","AT3*.tif"));
N = length(imds.Files);
tempCell = cell(N, 1);
for k = 1:N
    I = readimage(imds,k); % loop index!
    I = imrotate(I, 90);
    I = im2gray(I);
    tempCell{i} = I;
end
% create an image
outpict = imtile(tempCell);
% save the image
imwrite(outpict,'myfile.png')

... but it seems more that the images should be saved individually within the loop, so the use of montage() may be strictly for visualization.

imds = imageDatastore(fullfile(matlabroot,"toolbox","images","imdata","AT3*.tif"));
outputpath = '.'; % pick where they go
N = length(imds.Files);
for k = 1:N
    I = readimage(imds,k); % loop index!
    I = imrotate(I, 90);
    I = im2gray(I);
    
    % if the visualization is not needed,
    % the images can just be saved in the loop
    [~,fname,ext] = fileparts(imds.Files{k});
    thisfname = fullfile(outputpath,[fname ext]);
    imwrite(I,thisfname)
end