Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/image-1.0.15/bwdist.m b/octave_packages/image-1.0.15/bwdist.m
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+## Copyright (C) 2006  Stefan Gustavson
+## 
+## 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, 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 file.  If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{D} =} bwdist(@var{bw})
+##
+## Computes the distance transform of the image @var{bw}.
+## @var{bw} should be a binary 2D array, either a Boolean array or a
+## numeric array containing only the values 0 and 1.
+## The return value @var{D} is a double matrix of the same size as @var{bw}.
+## Elements with value 0 are considered background pixels, elements
+## with value 1 are considered object pixels. The return value
+## for each background pixel is the distance (according to the chosen
+## metric) to the closest object pixel. For each object pixel the
+## return value is 0.
+## 
+## @deftypefnx{Function File} {@var{D} =} bwdist(@var{bw}, @var{method})
+## 
+## @var{method} is a string to choose the distance metric. Currently
+## available metrics are 'euclidean', 'chessboard', 'cityblock' and
+## 'quasi-euclidean', which may each be abbreviated to any string
+## starting with 'e', 'ch', 'ci' and 'q', respectively.
+## If @var{method} is not specified, 'euclidean' is the default.
+## 
+## @deftypefnx {Function File} {[@var{D},@var{C}] =} bwdist(@var{bw}, @var{method})
+## 
+## If a second output argument is given, the linear index for the
+## closest object pixel is returned for each pixel. (For object
+## pixels, the index points to the pixel itself.) The return value
+## @var{C} is a matrix the same size as @var{bw}.
+## @end deftypefn
+
+# This M wrapper is an almost direct pass-through to an oct function,
+# but it might prove useful for a future extension to handle N-D data.
+# The algorithm implemented by __bwdist() is 2D-only.
+
+function [D, C] = bwdist(bw, method = "euclidean")
+  
+  if (!ischar(method))
+    error("bwdist: method name must be a string");
+  endif
+
+  if (nargout < 2)
+    D = __bwdist(bw, method);
+  else
+    [D, C] = __bwdist(bw, method);
+  endif
+
+endfunction