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--- /dev/null
+++ b/inst/isbw.m
@@ -0,0 +1,39 @@
+## Copyright (C) 2000  Kai Habel
+##
+## 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, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} @var{bool}= isbw (@var{BW})
+## returns true for a black-white (binary) image.
+## All values must be either 0 or 1
+## @end deftypefn
+
+## Author:	Kai Habel <kai.habel@gmx.de>
+## Date:	20/03/2000
+
+function bool = isbw (BW)
+
+  bool = 0;	
+  if !(nargin == 1)
+    usage ("isbw(BW)");
+  endif
+
+  if !(is_matrix(BW))
+    return;
+  endif
+
+  bool = all (all ((BW == 1) + (BW == 0)));
+
+endfunction