Add a useful package (from Source forge) for octave

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

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+## Copyright (C) 2004 Josep Mones i Teixidor
+##
+## 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{eul} = } bweuler (@var{BW},@var{n})
+## Calculates the Euler number of a binary image.
+##
+## @var{eul}=bweuler(@var{BW}, @var{n}) calculates the Euler number @var{eul} of a binary
+## image @var{BW}, which is a scalar whose value is the total number of
+## objects in an image minus the number of holes.
+##
+## @var{n} can have the values:
+## @table @code
+## @item 4
+## bweuler will use 4-connected neighbourhood definition.
+## @item 8
+## bweuler will use 8-connected neighbourhood definition. This is the
+## default value.
+## @end table
+##
+## This function uses Bit Quads as described in "Digital Image
+## Processing" to calculate euler number.
+##
+## References:
+## W. K. Pratt, "Digital Image Processing", 3rd Edition, pp 593-595
+##
+## @seealso{qtgetblk}
+## @end deftypefn
+
+## Author:  Josep Mones i Teixidor <jmones@puntbarra.com>
+
+function eul = bweuler(BW, n)
+  if(nargin<1 || nargin>2)
+    usage("eul=bweuler(BW,n)");
+  endif
+  if(nargin<2)
+    n=8;
+  endif
+
+  ## q1lut=makelut(inline("sum(x(:))==1","x"),2);
+  ## q3lut=makelut(inline("sum(x(:))==3","x"),2);
+  ## qdlut=makelut(inline("all((x==eye(2))(:))||all((x==fliplr(eye(2)))(:))","x"),2);
+  ## lut_4=(q1lut-q3lut+2*qdlut)/4;  # everything in one lut will be quicker
+  ## lut_8=(q1lut-q3lut-2*qdlut)/4;
+  ## we precalculate this...
+  if(n==8)
+    lut=[0;.25;.25;0;.25;0;-.5;-.25;.25;-.5;0;-.25;0;-.25;-.25;0];
+  elseif(n==4)
+    lut=[0;.25;.25;0;.25;0;.5;-.25;.25;.5;0;-.25;0;-.25;-.25;0];
+  else
+    error("bweuler: n can only be 4 or 8.");
+  endif
+  
+  eul=sum(applylut(BW,lut)(:));
+endfunction
+
+%!demo
+%! A=zeros(9,10);
+%! A([2,5,8],2:9)=1;
+%! A(2:8,[2,9])=1
+%! bweuler(A)
+%! # Euler number (objects minus holes) is 1-2=-1 in an 8-like object
+
+%!test
+%! A=zeros(10,10);
+%! A(2:9,3:8)=1;
+%! A(4,4)=0;
+%! A(8,8)=0; # not a hole
+%! A(6,6)=0;
+%! assert(bweuler(A),-1);
+
+%!# This will test if n=4 and n=8 behave differently
+%!test
+%! A=zeros(10,10);
+%! A(2:4,2:4)=1;
+%! A(5:8,5:8)=1;
+%! assert(bweuler(A,4),2);
+%! assert(bweuler(A,8),1);
+%! assert(bweuler(A),1);
+
+% $Log$
+% Revision 1.3  2007/03/23 16:14:36  adb014
+% Update the FSF address
+%
+% Revision 1.2  2007/01/04 23:41:47  hauberg
+% Minor changes in help text
+%
+% Revision 1.1  2006/08/20 12:59:31  hauberg
+% Changed the structure to match the package system
+%
+% Revision 1.2  2005/07/03 01:10:19  pkienzle
+% Try to correct for missing newline at the end of the file
+%
+% Revision 1.1  2004/08/15 19:33:20  jmones
+% bweuler: Calculates the Euler number of a binary image