82 lines
2.0 KiB
C++
82 lines
2.0 KiB
C++
// Copyright 2004 David Hilvert <dhilvert@auricle.dyndns.org>,
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// <dhilvert@ugcs.caltech.edu>
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/* This file is part of the Anti-Lamenessing Engine.
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The Anti-Lamenessing Engine is free software; you can redistribute it and/or modify
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it 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
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(at your option) any later version.
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The Anti-Lamenessing Engine is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU 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 the Anti-Lamenessing Engine; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef __lanczos_h__
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#define __lanczos_h__
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/*
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* A lanczos filter class.
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*
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* Notes on Lanczos and Sinc by Dave Martindale et alia are available here:
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*
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* http://www.binbooks.com/books/photo/i/l/57186AF8DE
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* http://www.binbooks.com/books/photo/i/l/57186AE7E6&orig=1
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*/
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class lanczos : public filter {
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private:
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ale_pos half_width;
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/*
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* Lanczos function
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*
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* The lanczos function is the central lobe of the sinc function.
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*/
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ale_real _lanczos(ale_pos p) const {
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if (fabs(p) >= half_width)
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return 0;
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return sinc::_sinc(p / half_width);
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}
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ale_real _lanczos(point p) const {
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return _lanczos(p[0]) * _lanczos(p[1]);
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}
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public:
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/*
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* Size of filter support, in number of half-cycles to each side of the
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* filter center.
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*/
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ale_pos support() const {
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return half_width;
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}
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virtual int equals(const filter *f) const {
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if (typeid(*f) == typeid(*this))
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return ((lanczos *)f)->half_width == half_width;
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return 0;
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}
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/*
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* Response of filter at point p
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*/
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virtual ale_real response(point p) const {
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return _lanczos(p);
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}
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lanczos(double half_width) {
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this->half_width = half_width;
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}
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};
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#endif
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