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+## Copyright (C) 2008 Søren Hauberg
+## 
+## 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 3 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{S} =} stdfilt (@var{im})
+## @deftypefnx{Function File} {@var{S} =} stdfilt (@var{im}, @var{domain})
+## @deftypefnx{Function File} {@var{S} =} stdfilt (@var{im}, @var{domain}, @var{padding}, ...)
+## Computes the local standard deviation in a neighbourhood around each pixel in
+## an image.
+##
+## The standard deviation of the pixels of a neighbourhood is computed as
+##
+## @example
+## @var{S} = sqrt ((sum (@var{x} - @var{mu}).^2)/(@var{N}-1))
+## @end example
+##
+## where @var{mu} is the mean value of the pixels in the neighbourhood,
+## @var{N} is the number of pixels in the neighbourhood. So, an unbiased estimator
+## is used.
+##
+## The neighbourhood is defined by the @var{domain} binary mask. Elements of the
+## mask with a non-zero value are considered part of the neighbourhood. By default
+## a 3 by 3 matrix containing only non-zero values is used.
+##
+## At the border of the image, extrapolation is used. By default symmetric
+## extrapolation is used, but any method supported by the @code{padarray} function
+## can be used. Since extrapolation is used, one can expect a lower deviation near
+## the image border.
+##
+## @seealso{std2, paddarray, entropyfilt}
+## @end deftypefn
+
+function retval = stdfilt (I, domain = true (3), padding = "symmetric", varargin)
+  ## Check input
+  if (nargin == 0)
+    error ("stdfilt: not enough input arguments");
+  endif
+  
+  if (!ismatrix (I))
+    error ("stdfilt: first input must be a matrix");
+  endif
+  
+  if (!ismatrix (domain))
+    error ("stdfilt: second input argument must be a logical matrix");
+  endif
+  domain = (domain > 0);
+  
+  ## Pad image
+  pad = floor (size (domain)/2);
+  I = padarray (I, pad, padding, varargin {:});
+  even = (round (size (domain)/2) == size (domain)/2);
+  idx = cell (1, ndims (I));
+  for k = 1:ndims (I)
+    idx {k} = (even (k)+1):size (I, k);
+  endfor
+  I = I (idx {:});
+
+  ## Perform filtering
+  retval = __spatial_filtering__ (I, domain, "std", I, 0);
+
+endfunction