Hi Carnë,
I have fixed two problems in this function. There was no validation of
the input image and there was a problem computing values when a figure
touches the top and left borders.
I want to submit the new version but the procedure seems a little
complex. Also, I don't know if I should write the log at the end of the
file.
I have attached the file to receive your comments.
Regards.
Adrián del Pino
On Mon, Nov 21, 2011 at 9:59 PM, Carnë Draug <carandraug+...@gmail.com>wrote:
> On 26 October 2011 16:19, Adrián del Pino <delpinonavarr...@gmail.com>
> wrote:
> > Dear Octave:
> > Sometimes the function bweuler returns incorrect values. By example,
> it
> > returns -0.5 instead of 1 with this image ("prueba3.tif"). Moreover, this
> > function should return integer values.
> >
> > Best regards.
> > Adrián del Pino
>
> Hi Adrián
>
> just to let you know that this was not forgotten. I was hoping that
> someone would show up and manage to fix it. As that doesn't seem to be
> happening, I added your report to the bug tracker here
>
> https://sourceforge.net/tracker/?func=detail&aid=3440926&group_id=2888&atid=102888
>
> It would be great if you were able to fix the problem and submit a
> patch for it. The function is written in the GNU octave language so it
> shouldn't be too hard provided you know the subject. The link for the
> latest revision of the file is
>
> http://octave.svn.sourceforge.net/viewvc/octave/trunk/octave-forge/main/image/inst/bweuler.m
>
> I have also CC'ed the dev that wrote this function.
>
> Carnë
>
## 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 <jmo...@puntbarra.com>
function eul = bweuler(BW, n)
if(nargin<1 || nargin>2)
usage("eul=bweuler(BW,n)");
end
if (isbw(BW)==0)
error("bweuler: image can only be B&W");
end
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
## adding zeros to the top and left bordes to avoid errors when figures touch these borders.
## For example, 1 0 gives 0.25 because there are three one-pixel and one diagonal pixels.
## 0 1
## So, we have 3*0.25 - 0.5 = 0.25 (error) instead of 1 (correct).
## Fortunately, there is no need to add zeros to the other borders.
[m,n]=size(BW);
BWaux=zeros(m+1,n+1);
for i=1:m
for j=1:n
BWaux(i+1,j+1)=BW(i,j);
end
end
eul=sum(applylut(BWaux,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
------------------------------------------------------------------------------
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