Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / image-1.0.15 / ordfiltn.m

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+## Copyright (C) 2008 Soren 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, see <http://www.gnu.org/licenses/>.
+##
+## This function is based on 'ordfilt2' by Teemu Ikonen which is released under
+## GPLv2 or later.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} ordfiltn(@var{A}, @var{nth}, @var{domain}, [@var{S}, @var{padding}])
+## Two dimensional ordered filtering.
+##
+## Ordered filter replaces an element of @var{A} with the @var{nth} 
+## element of the sorted set of neighbours defined by the logical 
+## (boolean) matrix @var{domain}.
+## Neighbour elements are selected to the sort if the corresponding 
+## element in the @var{domain} matrix is true.
+## 
+## The optional variable @var{S} is a matrix of size(@var{domain}). 
+## Values of @var{S} corresponding to nonzero values of domain are 
+## added to values obtained from @var{A} when doing the sorting.
+##
+## Optional variable @var{padding} determines how the matrix @var{A} 
+## is padded from the edges. See @code{padarray} for details.
+## 
+## @seealso{ordfilt2, padarray}
+## @end deftypefn
+
+
+## Author: Teemu Ikonen <tpikonen@pcu.helsinki.fi>
+## Created: 5.5.2000
+## Keywords: image processing filtering
+
+function retval = ordfiltn(A, nth, domain, varargin)
+  ## Check input
+  if (nargin < 3)
+    error("ordfiltn: not enough input arguments");
+  endif
+  if (!ismatrix(A))
+    error("ordfiltn: first input must be an array");
+  endif
+  if (!isscalar(nth) || nth <= 0 || nth != round(nth))
+    error("ordfiltn: second input argument must be a positive integer");
+  endif
+  if (!ismatrix(domain) && !isscalar(domain))
+    error("ordfiltn: third input argument must be an array or a scalar");
+  endif
+  if (isscalar(domain) && (domain <= 0 || domain != round(domain)))
+    error("ordfiltn: third input argument must be a positive integer, when it is a scalar");
+  endif
+  if (isscalar(domain))
+    domain = ones(repmat(domain, 1, ndims(A)), "logical");
+  endif
+  
+  if (ndims(A) != ndims(domain))
+    error("ordfiltn: first and second argument must have same dimensionality");
+  endif
+  if (any(size(A) < size(domain)))
+    error("ordfiltn: domain array cannot be larger than the data array");
+  endif    
+
+  ## Parse varargin
+  S = zeros(size(domain));
+  padding = 0;
+  for i=1:length(varargin)
+    a = varargin{:};
+    if (ischar(a) || isscalar(a))
+      padding = a;
+    elseif (ismatrix(a) && size_equal(a, domain))
+      S = a;
+    endif
+  endfor
+
+  ## Make sure 'domain' is logical. The C++ code assumes this.
+  domain = logical(domain);
+
+  ## Pad array
+  pad = floor(size(domain)/2);
+  A = padarray(A, pad, padding);
+  even = ( round(size(domain)/2) == size(domain)/2 );
+  idx = cell(1, ndims(A));
+  for k = 1:ndims(A)
+    idx{k} = (even(k)+1):size(A,k);
+  endfor
+  A = A(idx{:});
+  
+  ## Perform the filtering
+  retval = __spatial_filtering__ (A, domain, "ordered", S, nth);
+endfunction