Get inidces for specific conditions from binary mask

Dear MATLAB-Community,

I have a binary mask M (attached).

I would like to get the indices that match the following condition: Find all "1" that have at least one "0" as a neighboring entry.

I have tried a lot the last days but did not find a solution. It would be great if someone could help me with that.

Best regards!

Answer 1

[Walter Roberson]

NC  = conv2(M, [1 1 1; 1 0 1; 1 1 1], 'same');
mask = M & (NC < 8);
%now you can find() on mask

See also https://www.mathworks.com/help/images/ref/edge.html and https://www.mathworks.com/help/images/ref/bwperim.html

[PA]

Thank you very much for your help, this worked just fine!

Answer 2

[Image Analyst]

There is a built-in function for this in the Image Processing Toolbox. It's called bwperim(). Full demo:

s = load('m.mat')
M = s.M;
subplot(2, 1, 1);
imshow(M, [])
axis('on', 'image')
% Find all 1 that have a zero as a neighbor.
% We can use bwperim() for this
perimImage = bwperim(M);
subplot(2, 1, 2);
imshow(perimImage, [])
axis('on', 'image')

[PA]

Thank you very much for your help, this worked just fine!