How to rename an image after processing with different parameters

Hello dear programmers,

I have a sequence of images and I would like to perform dilation on each of them with different dilation parameters. Then, I would like to save the processed images with new name including both the old name and the corresponding dilation parameter. My codes are as follows.

```

Input_folder = 
Output_folder = 

D = dir([Input_folder '*.jpg']);
Inputs = {D.name}';
Outputs = Inputs; % preallocate

%print(length(Inputs));

for k = 1:length(Inputs)
    X = imread([Input_folder Inputs{k}]);
    dotLocations = find(Inputs{k} == '.');
    name_img = Inputs{k}(1:dotLocations(1)-1);
    image1=im2bw(X);
    vec = [3;6;10];
    vec_l = length(vec);
    for i = 1:vec_l
    %se = strel('disk',2);
        fprintf(num2str(vec(i)));
        se = strel('diamond',vec(i)); %imdilate
        im = imdilate(image1,se);
        image2 = im - image1;
   
        Outputs{k} = regexprep(Outputs{k}, name_img, strcat(name_img,'_', num2str(vec(i))));
        imwrite(image2, [Output_folder Outputs{k}])
    end
end

```

As it can be seen, I would like to apply dilation with parameters 3,6 and 10. Let us assume that an image has as name "image1", after processing it, I would like to have "image1_3", "image1_6" and "image1_10". However, I am getting as results "image1_3", "image1_6_3" and "image1_10_6_3". Please, how can I modify my codes to fix this problem?

Answer 1

[Stephen23]

The cause of the problem is that your inner loop repeatedly processes the same string of the cell array Outputs. So you just keep applying regexprep to the same name, each time adding to whatever you did on the last loop iteration.

The simplest solution would be to NOT use the cell array Outputs at all, but to always start again from the raw (input) filename, e.g. something like this (note how the filename N and extension E do not change in the inner loop):

Input_folder = 
Output_folder = 
S = dir(fullfile(Input_folder,'*.jpg'));
for ii = 1:numel(S)
    F = S(ii).name;
    X = imread(fullfile(Input_folder,F));
    I = im2bw(X);
    [~,N,E] = fileparts(F);
    V = [3;6;10];
    for jj = 1:numel(V)
        se = strel('diamond',V(jj)); %imdilate
        J = imdilate(I,se);
        Y = I - J;
        G = sprintf('%s_%d%s',N,V(jj),E);
        imwrite(Y,fullfile(Output_folder,G))
    end
end

Note that I also made some other improvements to your code, namely:

1. replaced fragile string concatenation with the recommended and robust fullfile.
2. replaced fragile '.' matching to locate file extension with the recommended and robust fileparts.
3. replaced regexprep and num2str with sprintf.

[Patrice Gaofei]

I have just tried your codes, and the names are correct now. However, the saved images are all black. Please, what could be reason?

I have been able to fix it as follows.

After performing dilation (J = imdilate(I,se)); the processed image should be Y = J- I; rather than Y = I - J;

Thank you very much for your time and help!