Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/image-1.0.15/bwarea.m b/octave_packages/image-1.0.15/bwarea.m
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+## Copyright (C) 2005  Søren Hauberg
+## 
+## 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 2 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{total}= bwarea(@var{bw})
+## Estimates the area of the "on" pixels of @var{bw}.
+## If @var{bw} is a binary image "on" pixels are defined as pixels
+## valued 1. If @var{bw} is a grayscale image "on" pixels is defined
+## as pixels with values larger than zero.
+## This algorithm is not the same as counting the number of "on"
+## pixels as it tries to estimate the area of the original object
+## and not the image object.
+## @end deftypefn
+
+## Author: Søren Hauberg <hauberg at gmail dot com>
+## 
+## 2005-06-05 Søren Hauberg <hauberg at gmail dot com>
+## * Initial revision
+
+
+function total = bwarea(bw)
+  if (isgray(bw))
+    bw = (bw > 0);
+  endif
+
+  if (!isbw(bw))
+    error("input image muste be either binary or gray scale.\n");
+  endif
+  
+  four = ones(2);
+  two  = diag([1 1]);
+
+  fours = conv2(bw, four);
+  twos  = conv2(bw, two);
+
+  nQ1 = sum(fours(:) == 1);
+  nQ3 = sum(fours(:) == 3);
+  nQ4 = sum(fours(:) == 4);
+  nQD = sum(fours(:) == 2 & twos(:) != 1);
+  nQ2 = sum(fours(:) == 2 & twos(:) == 1);
+
+  total = 0.25*nQ1 + 0.5*nQ2 + 0.875*nQ3 + nQ4 + 0.75*nQD;
+  
+endfunction