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## Copyright (C) 2001-2013 Paul Kienzle
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## This file is part of Octave.
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## Octave is free software; you can redistribute it and/or modify it
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## under the terms of the GNU General Public License as published by
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## the Free Software Foundation; either version 3 of the License, or (at
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## your option) any later version.
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## Octave is distributed in the hope that it will be useful, but
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## WITHOUT ANY WARRANTY; without even the implied warranty of
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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## General Public License for more details.
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## You should have received a copy of the GNU General Public License
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## along with Octave; see the file COPYING. If not, see
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## <http://www.gnu.org/licenses/>.
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## @deftypefn {Function File} {@var{y} =} filter2 (@var{b}, @var{x})
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## @deftypefnx {Function File} {@var{y} =} filter2 (@var{b}, @var{x}, @var{shape})
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## Apply the 2-D FIR filter @var{b} to @var{x}. If the argument
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## @var{shape} is specified, return an array of the desired shape.
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## Possible values are:
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## @item @qcode{"full"}
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## pad @var{x} with zeros on all sides before filtering.
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## @item @qcode{"same"}
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## unpadded @var{x} (default)
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## @item @qcode{"valid"}
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## trim @var{x} after filtering so edge effects are no included.
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## Note this is just a variation on convolution, with the parameters
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## reversed and @var{b} rotated 180 degrees.
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## Author: Paul Kienzle <pkienzle@users.sf.net>
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function y = filter2 (b, x, shape)
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if (nargin < 2 || nargin > 3)
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y = conv2 (x, b(nr:-1:1, nc:-1:1), shape);