How can I extract frequency values of intensity from multiple image files to one Excel file

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Mac 2023-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/2035299-how-can-i-extract-frequency-values-of-intensity-from-multiple-image-files-to-one-excel-file

评论： Dyuman Joshi 2023-10-18

Dear community,

I am trying to extract frequency values from histograms of multiple images (*.jpg) and then save data to an Excel file, using the following script.

However, it did not work. Please help me to extract data to one Excel file with data columns labled by the file name of image at first row.

Thank you very much,

// My code

path_directory='myfolder'; % 'myfolder' in my current directory

myfiles=dir([path_directory '/*.jpg']);

for k=1:length(myfiles)

filename=[path_directory '/' myfiles(k).name];

I=imread(filename);

I=rgb2gray(I);

[count,x]=imhist(I,25);

T=table(count);

writetable(T, 'frequency.xlsx');

end

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Answer 1

Dyuman Joshi 2023-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/2035299-how-can-i-extract-frequency-values-of-intensity-from-multiple-image-files-to-one-excel-file#answer_1335924

在 MATLAB Online 中打开

You have done almost everything correct. However, you are over-writing the excel file with each iteration, thus you will only get the values corresponding to the final file.

You can either store data for images in separate columns -

path_directory='myfolder'; % 'myfolder' in my current directory
myfiles=dir([path_directory '/*.jpg']);
%number of files
n = numel(myfiles);
%As it is known that there are 25 bins for categorizing data, the output
%will be a 25x1 vector, thus preallocate accordingly
count = zeros(25,n);
for k=1:n
      filename=[path_directory '/' myfiles(k).name];
      I=imread(filename);
      I=rgb2gray(I);
      count(:,k)=imhist(I,25);
end 
T = table(count);
writetable(T, 'frequency.xlsx');

Or you can store the data for images in separate sheets -

path_directory='myfolder'; % 'myfolder' in my current directory
myfiles=dir([path_directory '/*.jpg']); 
%number of files
n = numel(myfiles);
%preallocate worksheets
writetable(table(),'frequency.xlsx','Sheet', n);
for k=1:n
      filename=[path_directory '/' myfiles(k).name];
      I=imread(filename);
      I=rgb2gray(I);
      [count,x]=imhist(I,25);
      T=table(count);
      writetable(T, 'frequency.xlsx', 'Sheet', k);
end 