Fill area between two connected components in MATLAB

Question

I have a binary image that represents a number in MATLAB:

I'd like to fill all the digits. The desired result is:

The only thing I found was the imfill function, but that wasn't really helpfull since I've lost my inner data (the 9's inner circle for example).

Answer 1

Another possibility is to use the BWBOUNDARIES function, which:

traces the exterior boundaries of objects, as well as boundaries of holes inside these objects

That information is contained in the fourth output A, an adjacency matrix that represents the parent-child-hole dependencies.

%# read binary image
bw = imread('SUvif.png');

%# find all boundaries
[B,L,N,A] = bwboundaries(bw, 8, 'holes');

%# exclude inner holes
[r,~] = find(A(:,N+1:end));        %# find inner boundaries that enclose stuff
[rr,~] = find(A(:,r));                      %# stuff they enclose
idx = setdiff(1:numel(B), [r(:);rr(:)]);    %# exclude both
bw2 = ismember(L,idx);                      %# filled image

%# compare results
subplot(311), imshow(bw), title('original')
subplot(312), imshow( imfill(bw,'holes') ), title('imfill')
subplot(313), imshow(bw2), title('bwboundaries')