Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / image-1.0.15 / bwboundaries.m

diff --git a/octave_packages/image-1.0.15/bwboundaries.m b/octave_packages/image-1.0.15/bwboundaries.m
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+## Copyright (C) 2010 Soren Hauberg
+## Modified December 2010 by Andrew Kelly, IPS Radio & Space Services
+##
+## 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} {@var{boundaries} = } bwboundaries(@var{BW})
+## @deftypefnx {Function File} {@var{boundaries} = } bwboundaries(@var{BW}, @var{conn})
+## @deftypefnx {Function File} {@var{boundaries} = } bwboundaries(@var{BW}, @var{conn}, @var{holes})
+## @deftypefnx {Function File} {[@var{boundaries}, @var{labels}] = } bwboundaries(@dots{})
+## @deftypefnx {Function File} {[@var{boundaries}, @var{labels}, @var{num_labels}] = } bwboundaries(@dots{})
+## Trace the boundaries of the objects in a binary image.
+##
+## @var{boundaries} is a cell array in which each element is the boundary of an
+## object in the binary image @var{BW}. The clockwise boundary of each object is 
+## computed by the @code{boundary} function.
+##
+## By default the boundaries are computed using 8-connectivity. This can be 
+## changed to 4-connectivity by setting @var{conn} to 4.
+##
+## By default @code{bwboundaries} computes all boundaries in the image, i.e.
+## both interior and exterior object boundaries. This behaviour can be changed
+## through the @var{holes} input argument. If this is @t{'holes'},
+## both boundary types are considered. If it is instead @t{'noholes'}, only exterior
+## boundaries will be traced.
+##
+## If two or more output arguments are requested, the algorithm also returns
+## the labelled image computed by @code{bwlabel} in @var{labels}. The number
+## of labels in this image is optionally returned in @var{num_labels}.
+## @seealso{boundary, bwlabel}
+## @end deftypefn
+
+function [bound, labels, num_labels] = bwboundaries (bw, conn=8, holes="holes")
+  # check arguments
+  if (nargin < 1)
+    error ("bwboundaries: not enough input arguments");
+  endif
+  if (!ismatrix (bw) || ndims (bw) != 2)
+    error ("bwboundaries: first input argument must be a NxM matrix");
+  endif
+  if (!isscalar (conn) || (conn != 4 && conn != 8))
+    error ("bwboundaries: second input argument must be 4 or 8");
+  endif
+  if (!ischar (holes) || !any (strcmpi (holes, {'holes', 'noholes'})))
+    error ("bwboundaries: third input must be either \'holes\' or \'noholes\'");
+  endif
+  
+  bw = logical (bw);
+  
+  # process each connected region separately
+  [labels, num_labels] = bwlabel (bw, conn);
+  bound = cell (num_labels, 1);
+  for k = 1:num_labels
+    bound {k} = __boundary__ ((labels == k), conn);
+  endfor
+  
+  # compute internal boundaries as well?
+  if (strcmpi (holes, "holes"))
+    filled = bwfill (bw, "holes", conn);
+    holes = (filled & !bw);
+    [intBounds, intLabels, numIntLabels] = bwboundaries (holes, conn, "noholes");
+
+    bound (end+1 : end+numIntLabels, 1) = intBounds;
+    intLabels (intLabels != 0) += num_labels;
+    labels += intLabels;
+  endif
+endfunction
+
+%!demo
+%! ## Generate a simple image
+%! bw = false (100);
+%! bw (10:30, 40:80) = true;
+%! bw (40:45, 40:80) = true;
+%!
+%! ## Find boundaries
+%! bounds = bwboundaries (bw);
+%!
+%! ## Plot result
+%! imshow (bw);
+%! hold on
+%! for k = 1:numel (bounds)
+%!   plot (bounds {k} (:, 2), bounds {k} (:, 1), 'r', 'linewidth', 2);
+%! endfor
+%! hold off