% -*- 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