How can I store 10 strongest points of surf features of multiple images in one variable using matlab?

i have 40 images i extract the surf features 10 strongest points in a loop but the variable where i stored the values, it gives me the values of last image i.e. 10x2 values. i want to save the values for all 40 images in that single variable.how can i get for all images?? for 40 images my desired result is 40x 2. any help will be really appreciated.thanks

[Farman Shah]

this is my code

srcFiles = dir('mypath\*.jpg');
for i = 1 : length(srcFiles)
        filename = strcat('mypath',srcFiles(i).name);
        input_images = imread(filename);
        I2=rgb2gray(input_images);
        points1 = detectSURFFeatures(input_images)
        strongest = points1.selectStrongest(10);
        %  
        plot(strongest);
        strong= round(strongest.Location);
end

[Stephen23]

Farman Shah's "Answer" moved here:

the code is working fine but stores only the 10 strongest points of the last image ..i want it to sotre for multiple images in a single variable.so then i can label it for further classification..any hope???

Answer 1

[Stephen23]

Just use a cell array and indexing:

D = 'mypath';
S = dir(fullfile(D,'*.jpg'));
N = numel(S);
C = cell(1,N);
for kk = 1:N
    filename = fullfile(D,S(kk).name);
    ...
    strongest = points1.selectStrongest(10);
    C{kk} = strongest;    
end

Then the strongest values for each loop iteration are stored in the cell array C.

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

It is recommended to use fullfile rather than concatenating strings and messing about with file separactor characters.

[Farman Shah]

thank you so much ..but it returns nothing..all the variables are empty.is there another way??

[Stephen23]

"but it returns nothing..all the variables are empty.is there another way??"

If your original code worked and strongest contained some values (which I have no way to check), then this answer should work too. How are you checking what the variable C contains? Please show use the exact code that you are using.

[Farman Shah]

this is my exact code

srcFiles = dir('C:\Users\FARMAN SHAH\Documents\PSL\catageroies\I_bay_Segmented_training\*.jpg');
for i = 1 : length(srcFiles)
    filename = strcat('C:\Users\FARMAN SHAH\Documents\PSL\catageroies\I_bay_Segmented_training\',srcFiles(i).name);
    input_images = imread(filename);
    points1 = detectSURFFeatures(input_images)
    strongest = points1.selectStrongest(10); 
    plot(strongest);
    strong= round(strongest.Location);
end

[Farman Shah]

strong= round(strongest.Location); actually contains the loaction of 10 strongest location points..it gives points for only last image..i need it for all 40 images in the same variable as 10 for fisrt 10 for 2nd and so one...

[Farman Shah]

i run your code

D = 'C:\Users\FARMAN SHAH\Documents\PSL\catageroies\I_bay_Segmented_training\*.jpg';
S = dir(fullfile(D,'*.jpg'));
N = numel(S);
C = cell(1,N);

gives me N= empty C= 1x0 cell and S= 0x1 struct

[Stephen23]

"i run your code"

In my answer variable D contains only the folder path, it does NOT contain the file match pattern, like you did. Follow what I wrote in my answer and it will work:

D = 'C:\Users\FARMAN SHAH\Documents\PSL\catageroies\I_bay_Segmented_training';
S = dir(fullfile(D,'*.jpg'));

We already defined the folder in variable D, so why do you write it all out again inside the loop? Waste of time. Do NOT use strcat, fullfile is clearer and easier to use, e.g. inside the loop:

filename = fullfile(D,S(kk).name);

[Farman Shah]

thank you so much again.this is very nice..it is runing perfect and returns 1x40 cells..each cell holds points for each image..one more thing can i get i these values (of 40 images) into a single sheet or file or something else? basically i want to labels these values and classify through svm..is it possible to get all these values into a single sheet or file or something like it?

[Stephen23]

@Farman Shah: saving cornerPoints objects, like the ones returned from the method selectStrongest, its really quite a different topic from this question. Maybe it is not even required. I recommend that you ask a new question asking about how to save these objects. Make sure to include a link to this question.

[Farman Shah]

okay thank you so much stephen Cobeldick sir..your idea was great and helpful...i asked another question. please have a look of that question too..

[fadi ssuhimat]

Did you find the answer?

I have same problem exactly?