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+## Copyright (C) 2013 CarnĂŤ Draug <carandraug@octave.org>
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} bwareaopen (@var{bw}, @var{lim})
+## @deftypefnx {Function File} {} bwareaopen (@var{bw}, @var{lim}, @var{conn})
+## Perform area opening.
+##
+## Remove objects with less than @var{lim} elements from a binary image
+## @var{bw}.
+##
+## Element connectivity @var{conn}, to define the size of objects, can be
+## specified with a numeric scalar (number of elements in the neighborhood):
+##
+## @table @samp
+## @item 4 or 8
+## for 2 dimensional matrices;
+## @item 6, 18 or 26
+## for 3 dimensional matrices;
+## @end table
+##
+## or with a binary matrix representing a connectivity array.  Defaults to
+## @code{conndef (ndims (@var{bw}), "maximal")} which is equivalent to
+## @var{conn} of 8 and 26 for 2 and 3 dimensional matrices respectively.
+##
+## @seealso{bwconncomp, conndef, bwboundaries}
+## @end deftypefn
+
+function bw = bwareaopen (bw, lim, conn)
+
+  if (nargin < 2 || nargin > 3)
+    print_usage ();
+  elseif (! ismatrix (bw) || ! (isnumeric (bw) || islogical (bw)))
+    error ("bwareaopen: BW must be an a numeric matrix");
+  elseif (! isnumeric (lim) || ! isscalar (lim) || lim < 0 || fix (lim) != lim)
+    error ("bwareaopen: LIM must be a non-negative scalar integer")
+  endif
+
+  if (nargin < 3)
+    ## Defining default connectivity here because it's dependent
+    ## on the first argument
+    conn = conndef (ndims (bw), "maximal");
+  else
+    conn = make_conn ("bwareaopen", 3, ndims (bw), conn);
+  endif
+
+  ## Output is always of class logical
+  bw = logical (bw);
+
+  ## We only have work to do when lim > 1
+  if (lim > 1)
+    idx_list = bwconncomp (bw, conn).PixelIdxList;
+    ind = cell2mat (idx_list (cellfun ("numel", idx_list) < lim)');
+    bw(ind) = false;
+  endif
+
+endfunction
+
+%!test
+%! in = [ 0   0   1   0   0   1   0   1   0   0
+%!        0   0   1   0   0   0   0   0   1   1
+%!        1   0   0   0   0   1   1   0   0   0
+%!        1   0   0   0   1   0   0   0   0   0
+%!        1   1   1   1   0   0   0   0   0   1
+%!        0   1   0   1   1   0   0   1   0   0
+%!        1   0   0   0   1   0   0   0   0   0
+%!        0   0   0   1   1   0   0   1   0   0
+%!        0   1   0   1   1   0   0   1   1   0
+%!        0   1   0   1   1   1   0   0   1   0];
+%! assert (bwareaopen (in, 1, 4), logical (in))
+%!
+%! out = [0   0   0   0   0   0   0   0   0   0
+%!        0   0   0   0   0   0   0   0   0   0
+%!        1   0   0   0   0   0   0   0   0   0
+%!        1   0   0   0   0   0   0   0   0   0
+%!        1   1   1   1   0   0   0   0   0   0
+%!        0   1   0   1   1   0   0   0   0   0
+%!        0   0   0   0   1   0   0   0   0   0
+%!        0   0   0   1   1   0   0   0   0   0
+%!        0   0   0   1   1   0   0   0   0   0
+%!        0   0   0   1   1   1   0   0   0   0];
+%! assert (bwareaopen (logical (in), 10, 4), logical (out))
+%! assert (bwareaopen (in, 10, 4), logical (out))
+%! assert (bwareaopen (in, 10, [0 1 0; 1 1 1; 0 1 0]), logical (out))
+%!
+%! out = [0   0   0   0   0   0   0   0   0   0
+%!        0   0   0   0   0   0   0   0   0   0
+%!        1   0   0   0   0   1   1   0   0   0
+%!        1   0   0   0   1   0   0   0   0   0
+%!        1   1   1   1   0   0   0   0   0   0
+%!        0   1   0   1   1   0   0   0   0   0
+%!        1   0   0   0   1   0   0   0   0   0
+%!        0   0   0   1   1   0   0   0   0   0
+%!        0   0   0   1   1   0   0   0   0   0
+%!        0   0   0   1   1   1   0   0   0   0];
+%! assert (bwareaopen (in, 10, 8), logical (out))
+%! assert (bwareaopen (in, 10, ones (3)), logical (out))
+%! assert (bwareaopen (in, 10), logical (out))
+%!
+%! out = [0   0   0   0   0   0   0   0   0   0
+%!        0   0   0   0   0   0   0   0   0   0
+%!        1   0   0   0   0   0   0   0   0   0
+%!        1   0   0   0   0   0   0   0   0   0
+%!        1   1   1   1   0   0   0   0   0   0
+%!        0   1   0   1   1   0   0   0   0   0
+%!        0   0   0   0   1   0   0   0   0   0
+%!        0   0   0   1   1   0   0   1   0   0
+%!        0   0   0   1   1   0   0   1   1   0
+%!        0   0   0   1   1   1   0   0   1   0];
+%! assert (bwareaopen (in, 4, [1 1 0; 1 1 1; 0 1 1]), logical (out))
+
+%!error bwareaopen ("not an image", 78, 8)
+%!error bwareaopen (rand (10) > 0.5, 10, 100)
+%!error bwareaopen (rand (10) > 0.5, 10, "maximal")
+%!error bwareaopen (rand (10) > 0.5, 10, [1 1 1; 0 1 1; 0 1 0])

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