How to make a loop on objects after watershed segmentation

I want to find objects with mean grayscale value <30 after watershed segmentation. But I don't know how to write the loop.After watershed, I think it is the segmented image is in label matrix (but not exactly sure). Could anyone give me a hand on writing this loop? Any help is appreciated.

Answer 1

[Matt J]

No need for a loop,

stats=regionprops(labelmatrix, grayvalues, 'MeanIntensity');

index=[stats.MeanIntensity]<30;

[Tian Tian]

Thank you! In this way, how can I view the objects with the index in the image?

[Matt J]

You mean how would you know, for example, which object corresponds to label number=2? One way would be to display the labelmatrix next to the original gray value image. The output structure "stats" will be ordered so that stats(i) corresponds to label number i.

[Tian Tian]

Sorry I feel a little bit confused. After applying the index (in your first comment), how can the object that selected using index be shown in the image to be view?

[Image Analyst]

You can loop through (untested):

for k = 1 : length(stats)
    if index(k)
        % Intensity is < 30
        mask = ismember(labelmatrix, k); % Get this one blob only.
        outputImage = grayImage; % Initialize
        outputImage(~mask) = 0; % Blacken outside mask
        figure; % Bring up new figure
        imshow(outputImage, []);
    end
end

[Tian Tian]

Thank you for this loop. I am trying this, but there is always unexpected errors about my code. If it is possible, may you please have a look?

 T = stats;

    excelfilename = 'Picture2.xlsx';
    writetable(T,excelfilename,'Sheet',1,'Range','A1');
    column=xlsread(excelfilename, 'A:A')
    H=length(column)

    dbstop if error
    for n = 1 : H
        MeanIntensity(n)= T(n,'MeanIntensity')
        if (MeanIntensity(n)<30)
            % Intensity is < 30
            mask = ismember(cc, n); 
            outputImage = I; 
            outputImage(~mask) = 0; 
            figure; % Bring up new figure
            imshow(outputImage , []);
        end
    end

The error is "You cannot subscript a table using linear indexing (one subscript) or multidimensional indexing (three or more subscripts). Use a row subscript and a variable subscript." Thank you for your time in advance.

[Matt J]

@Tian Tian,

Please close this question (by Accept-clicking) and start a new one. The issue in your posted question has been addressed. The discussion is now well into other unrelated issues.