%% Copyright (C) 2000  Etienne Grossmann
%%
%% 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

%%       b = mybwperim(im)
%%
%% b is the borders in the 0-1 matrix im. 4-neighborhood is considered.
%% 
%% A pixel is on the border if it is set in im, and it has at least one
%% neighbor that is not set.

%% Author:        Etienne Grossmann  <etienne@isr.ist.utl.pt>
%% Last modified: January 2000

%% matlab port - T.Breckon 19/11/04

function b = mybwperim(im)

[R,C]=size(im);

b = im & ~([im(2:R,:) ;  zeros(1,C) ] & [zeros(1,C); im(1:R-1,:) ] & [im(:,2:C) ,  zeros(R,1) ] & [zeros(R,1),  im(:,1:C-1)] ) ;