removing specific (innermost) feature in bw mask

Dear all,

i have the following bw mask:

where i can see 6 connected loops: on outer, one inner, and 4 small ones between. I need to remove the inner loop from this mask. it should be scalable to doing this operation for ~80'000 images of 320*320 pixels on a i7 porcessor.

what would certainly work for all 80k images is:

1) specify center point of the image (≈symmetry center of those loops);

2) turn all connected black pixels to white;

3) do the same with black;

4) done.

how can I do this or remove the inner loop in a different way? i did browse https://ch.mathworks.com/help/images/morphological-filtering.html but i didnt find what i look for. Thanks!

Answer 1

[Matlabber 1.0]

found it after 2 more minutes of searching^^ the double imfill with a ~ (not()) does the job:

 imshow(~imfill(~imfill(km~=0,[160,160]),[160,160]))
does the job