How to convert nearest pixel as same number of pixels value from gray image? like bwlabel?

How to convert nearest pixel as same number of pixels value from gray image? like bwlabel?

Answer 1

[Charu]

Hello Voxey,

According to my understanding of the question you want to label connected components in a grayscale image.

The function “bwlabel” works only for binary images, for grayscale images, you can use “bwlabeln” with logical conditions You can also use “bwconncomp” and “labelmatrix” functions in a loop for each unique value.

You can refer to the steps mentioned below to get label connected components in a grayscale image:

- Let I be the grayscale image.

I = [
    1 1 2 2;
    1 0 0 2;
    3 3 0 2
];

- Find the unique values (excluding background e.g.:0)

vals = unique(I);
vals(vals == 0) = []; 
% Remove background if needed

- Initialse label matrix

L = zeros(size(I));
label_count = 0;

- Loop through each value and label connected components.

L = zeros(size(I), 'double');
% Make sure L is double
label_count = 0;
for k = 1:length(vals)
    mask = I == vals(k);
    CC = bwconncomp(mask, 8); 
% 8-connectivity for 2D images
    temp_labels = double(labelmatrix(CC)); % Convert to double
    temp_labels(temp_labels > 0) = temp_labels(temp_labels > 0) + label_count;
    L(mask) = temp_labels(mask); 
    label_count = max(L(:));
end

L is the labelled image and each connected region of the same value has a unique label.

Here is the image generated on sample data, with unique label for grayscale:

For more information on the functions, kindly refer to the link of MathWorks documentation mentioned below:

-bwlabeln:

https://www.mathworks.com/help//releases/R2021a/images/ref/bwlabel.html

-bwconncomp:

https://www.mathworks.com/help/images/ref/bwconncomp.html

Hope this helps!