Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / image-1.0.15 / medfilt2.m

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+## Copyright (C) 2000 Teemu Ikonen
+##
+## 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, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} medfilt2(@var{A}, [@var{domain}, @var{padding}])
+## Two dimensional median filtering.
+##
+## Replaces elements of @var{A} with the median of their neighbours defined 
+## by true elements of logical matrix @var{domain}. The default @var{domain} 
+## is a 3 by 3 matrix with all elements equal to 1. If @var{domain} is 1 by 2
+## row vector, the domain matrix will be 
+## logical(ones(@var{domain}(2), @var{domain}(1))).
+##
+## Optional variable @var{padding} defines the padding used in augmenting 
+## the borders of @var{A}. See impad for details.
+##
+## @seealso{ordfilt2}
+## @end deftypefn
+
+## Author: Teemu Ikonen <tpikonen@pcu.helsinki.fi>
+## Created: 5.5.2000
+## Keywords: image processing median filtering
+
+%!test
+%! b = [0,1,2,3;1,8,12,12;4,20,24,21;7,22,25,18];
+%! assert(medfilt2(b),[0,1,2,0;1,4,12,3;4,12,20,12;0,7,20,0]);
+
+function retval = medfilt2(A, varargin)
+
+padding = "zeros";
+domain = logical(ones(3,3));
+
+for i=1:length(varargin)
+  a = varargin{i};
+  if(ischar(a))
+    padding = a;
+  elseif(isvector(a) && size(a) == [1, 2])
+    domain = logical(ones(a(2), a(1)));
+  elseif(ismatrix(a))
+    domain = logical(a);
+  endif
+endfor
+
+n = sum(sum(domain));
+if((n - 2*floor(n/2)) == 0) % n even - more work
+  nth = floor(n/2);
+  a = ordfilt2(A, nth, domain, padding);
+  b = ordfilt2(A, nth + 1, domain, padding);
+  retval = a./2 + b./2; # split into two divisions to avoid overflow on integer data
+else
+  nth = floor(n/2) + 1;
+  retval = ordfilt2(A, nth, domain, padding);
+endif
+
+endfunction