d2/filter/triangle.h

   1 // Copyright 2004 David Hilvert <dhilvert@auricle.dyndns.org>,
   2 //                              <dhilvert@ugcs.caltech.edu>
   3
   4 /*  This file is part of the Anti-Lamenessing Engine.
   5
   6     The Anti-Lamenessing Engine is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     The Anti-Lamenessing Engine is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License
  17     along with the Anti-Lamenessing Engine; if not, write to the Free Software
  18     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19 */
  20
  21 #ifndef __triangle_h__
  22 #define __triangle_h__
  23
  24 /*
  25  * A triangle filter class.
  26  */
  27
  28 class triangle : public filter {
  29 private:
  30         ale_real half_width;
  31
  32         /*
  33          * Triangle filter.
  34          */
  35         double _triangle(ale_pos p) const {
  36                 if (fabs(p) >= half_width)
  37                         return 0;
  38
  39                 return (1 - fabs(p) / half_width);
  40         }
  41
  42         double _triangle(point p) const {
  43                 return _triangle(p[0]) * _triangle(p[1]);
  44         }
  45
  46 public:
  47
  48         /*
  49          * Size of filter support, in number of half-cycles to each side of the
  50          * filter center.
  51          */
  52         virtual ale_real support() const {
  53                 return half_width;
  54         }
  55
  56         virtual int equals(const filter *f) const {
  57                 if (typeid(*f) == typeid(*this))
  58                         return ((triangle *)f)->half_width == half_width;
  59                 return 0;
  60         }
  61
  62         /*
  63          * Response of filter at point p
  64          */
  65         virtual ale_real response(point p) const {
  66                 return _triangle(p);
  67         }
  68
  69         triangle(ale_real half_width) {
  70                 this->half_width = half_width;
  71         }
  72
  73 };
  74 #endif