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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, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
## -*- texinfo -*-
## @deftypefn {Function File} {@var{B} = } nlfilter (@var{A}, [@var{m},@var{n}], @var{fun})
## @deftypefnx {Function File} {@var{B} = } nlfilter (@var{A}, [@var{m},@var{n}], @var{fun}, ...)
## @deftypefnx {Function File} {@var{B} = } nlfilter (@var{A},'indexed', ...)
## Processes image in sliding blocks using user-supplied function
##
## @code{B=nlfilter(A,[m,n],fun)} passes sliding @var{m}-by-@var{n}
## blocks to user-supplied function @var{fun}. A block is build for
## every pixel in @var{A}, such as it is centered within the block.
## @var{fun} must return a scalar, and it is used to create matrix
## @var{B}. @var{nlfilter} pads the @var{m}-by-@var{n} block at the
## edges if necessary.
##
## Center of block is taken at ceil([@var{m},@var{n}]/2).
##
## @code{B=nlfilter(A,[m,n],fun,...)} behaves as described above but
## passes extra parameters to function @var{fun}.
##
## @code{B=nlfilter(A,'indexed',...)} assumes that @var{A} is an indexed
## image, so it pads the image using proper value: 0 for uint8 and
## uint16 images and 1 for double images. Keep in mind that if 'indexed'
## is not specified padding is always done using 0.
##
## @end deftypefn
## @seealso{colfilt,blkproc,inline}
## Author: Josep Mones i Teixidor <jmones@puntbarra.com>
function B = nlfilter(A, varargin)
if(nargin<3)
error("nlfilter: invalid number of parameters.");
endif
## check 'indexed' presence
indexed=false;
p=1;
if(ischar(varargin{1}) && strcmp(varargin{1}, "indexed"))
indexed=true;
p+=1;
if(isa(A,"uint8") || isa(A,"uint16"))
padval=0;
else
padval=1;
endif
else
padval=0;
endif
## check [m,n]
if(!isvector(varargin{p}))
error("nlfilter: expected [m,n] but param is not a vector.");
endif
if(length(varargin{p})!=2)
error("nlfilter: expected [m,n] but param has wrong length.");
endif
sblk=varargin{p}(:);
p+=1;
## check fun
## TODO: add proper checks for this one
if(nargin<p)
error("nlfilter: required parameters haven't been supplied.");
endif
fun=varargin{p};
## remaining params are params to fun
## extra params are p+1:nargin-1
## We take an easy approach... feel free to optimize it (coding this
## in C++ would be a great idea).
## Calculate center of block
c=ceil(sblk/2);
## Pre-padding
prepad=c-ones(2,1);
## Post-padding
postpad=sblk-c;
## Save A size
as=size(A);
## Pad data
if(all(prepad==postpad))
if(any(prepad>0))
A=padarray(A,prepad,padval,'both');
endif
else
if(any(prepad>0))
A=padarray(A,prepad,padval,'pre');
endif
if(any(postpad>0))
A=padarray(A,postpad,padval,'post');
endif
endif
## calc end offsets
me=postpad(1)+prepad(1);
ne=postpad(2)+prepad(2);
## We concatenate everything to preserve fun return type
for i=1:as(1)
r=feval(fun,A(i:i+me,1:1+ne),varargin{p+1:nargin-1});
for j=2:as(2)
r=horzcat(r,feval(fun,A(i:i+me,j:j+ne),varargin{p+1:nargin-1}));
endfor
if(i==1)
B=r;
else
B=vertcat(B,r);
endif
endfor
endfunction
%!demo
%! nlfilter(eye(10),[3,3],inline("any(x(:)>0)","x"))
%! # creates a "wide" diagonal
%!assert(nlfilter(eye(4),[2,3],inline("sum(x(:))","x")),[2,2,1,0;1,2,2,1;0,1,2,2;0,0,1,1]);
%!assert(nlfilter(eye(4),'indexed',[2,3],inline("sum(x(:))","x")),[4,2,1,2;3,2,2,3;2,1,2,4;4,3,4,5]);
%!assert(nlfilter(eye(4),'indexed',[2,3],inline("sum(x(:))==y","x","y"),2),[0,1,0,1;0,1,1,0;1,0,1,0;0,0,0,0]!=0);
% Check uint8 and uint16 padding
%!assert(nlfilter(uint8(eye(4)),'indexed',[2,3],inline("sum(x(:))","x")),[2,2,1,0;1,2,2,1;0,1,2,2;0,0,1,1]);
%!assert(nlfilter(uint16(eye(4)),'indexed',[2,3],inline("sum(x(:))","x")),[2,2,1,0;1,2,2,1;0,1,2,2;0,0,1,1]);
% Check if function class is preserved
%!assert(nlfilter(uint8(eye(4)),'indexed',[2,3],inline("int8(sum(x(:)))","x")),int8([2,2,1,0;1,2,2,1;0,1,2,2;0,0,1,1]));
%
% $Log$
% Revision 1.5 2005/09/08 02:00:17 pkienzle
% [for Bill Denney] isstr -> ischar
%
% Revision 1.4 2004/11/15 16:04:20 pkienzle
% Fix tests for functions which return boolean matrices
%
% Revision 1.3 2004/09/03 13:28:32 jmones
% Corrected behaviour for int* and uint* types
%
% Revision 1.2 2004/08/15 19:43:11 jmones
% corrected a typo in doc
%
% Revision 1.1 2004/08/15 19:42:14 jmones
% nlfilter: Processes image in siliding blocks using user-supplied function
%
%

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