% FINDDISCONNECTED find groupings of disconnected labeled regions
%
% Usage: list = finddisconnected(l)
%
% Argument: l - A labeled image segmenting an image into regions, such as
% might be produced by a graph cut or superpixel algorithm.
% All pixels in each region are labeled by an integer.
%
% Returns: list - A cell array of lists of regions that are not
% connected. Typically there are 5 to 6 lists.
%
% Used by MCLEANUPREGIONS to reduce the number of morphological closing
% operations
%
% See also: MCLEANUPREGIONS, REGIONADJACENCY
% Copyright (c) 2013 Peter Kovesi
% www.peterkovesi.com/matlabfns/
%
% Permission is hereby granted, free of charge, to any person obtaining a copy
% of this software and associated documentation files (the "Software"), to deal
% in the Software without restriction, subject to the following conditions:
%
% The above copyright notice and this permission notice shall be included in
% all copies or substantial portions of the Software.
%
% The Software is provided "as is", without warranty of any kind.
% PK July 2013
function list = finddisconnected(l)
debug = 0;
[Am, Al] = regionadjacency(l);
N = max(l(:)); % number of labels
% Array for keeping track of visited labels
visited = zeros(N,1);
list = {};
listNo = 0;
for n = 1:N
if ~visited(n)
listNo = listNo + 1;
list{listNo} = n;
visited(n) = 1;
% Find all regions not directly connected to n and not visited
notConnected = setdiff(find(~Am(n,:)), find(visited));
% For each unconnected region check that it is not already
% connected to a region in the list. If not, add to list
for m = notConnected
if isempty(intersect(Al{m}, list{listNo}))
list{listNo} = [list{listNo} m];
visited(m) = 1;
end
end
end % if not visited(n)
end
% Display each list of unconncted regions as an image
if debug
for n = 1:length(list)
mask = zeros(size(l));
for m = 1:length(list{n})
mask = mask | l == list{n}(m);
end
fprintf('list %d of %d length %d \n', n, length(list), length(list{n}))
show(mask);
keypause
end
end