1## Copyright (C) 2005 Søren Hauberg <soren@hauberg.org>
2##
3## This program is free software; you can redistribute it and/or modify it under
4## the terms of the GNU General Public License as published by the Free Software
5## Foundation; either version 3 of the License, or (at your option) any later
6## version.
7##
8## This program is distributed in the hope that it will be useful, but WITHOUT
9## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
11## details.
12##
13## You should have received a copy of the GNU General Public License along with
14## this program; if not, see <http://www.gnu.org/licenses/>.
15
16## -*- texinfo -*-
17## @deftypefn {Function File} {@var{total} =} bwarea (@var{bw})
18## Estimate total area of objects on the image @var{bw}.
19##
20## The image @var{bw} can be of any class, even non-logical, in which case non
21## zero valued pixels are considered to be an object.
22##
23## This algorithm is not the same as counting the number of pixels belonging to
24## an object as it tries to estimate the area of the original object.  The value
25## of each pixel to the total area is weighted in relation to its neighbour
26## pixels.
27##
28## @seealso{im2bw, bweuler, bwperim, regionprops}
29## @end deftypefn
30
31function total = bwarea (bw)
32  if (nargin != 1)
33    print_usage;
34  elseif (!isimage (bw) || ndims (bw) != 2)
35    error("bwarea: input image must be a 2D image");
36  elseif (!islogical (bw))
37    bw = (bw != 0)
38  endif
39
40  four = ones (2);
41  two  = diag ([1 1]);
42
43  fours = conv2 (bw, four);
44  twos  = conv2 (bw, two);
45
46  nQ1 = sum (fours(:) == 1);
47  nQ3 = sum (fours(:) == 3);
48  nQ4 = sum (fours(:) == 4);
49  nQD = sum (fours(:) == 2 & twos(:) != 1);
50  nQ2 = sum (fours(:) == 2 & twos(:) == 1);
51
52  total = 0.25*nQ1 + 0.5*nQ2 + 0.875*nQ3 + nQ4 + 0.75*nQD;
53
54endfunction
55