--- a/INDEX
+++ b/INDEX
@@ -100,3 +100,4 @@
  poly2mask
  bestblk
  blkproc
+ nlfilter

new file mode 100644
--- /dev/null
+++ b/nlfilter.m
@@ -0,0 +1,143 @@
+## 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 siliding 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(isstr(varargin{1}) && strcmp(varargin{1}, "indexed"))
+    indexed=true;
+    p+=1;
+    if(strcmp(typeinfo(A), 'uint8 matrix'))
+      padval=0; ## padval=uint8(0); in future...
+    elseif(strcmp(typeinfo(A), 'uint16 matrix'))
+      padval=0; ## padval=uint16(0); in future...
+    else
+      padval=1; ## array of double
+    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;
+  
+  ## Create room in output matrix
+  B=zeros(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);
+	
+  ## Fill it!
+  for i=1:rows(B)
+    for j=1:columns(B)
+      B(i,j)=feval(fun,A(i:i+me,j:j+ne),varargin{p+1:nargin-1});
+    endfor
+  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]);
+
+
+
+%
+% $Log$
+% Revision 1.1  2004/08/15 19:42:14  jmones
+% nlfilter: Processes image in siliding blocks using user-supplied function
+%
+%
\ No newline at end of file