libs/filters/GP_Cubic.h

   1 /*****************************************************************************
   2  * This file is part of gfxprim library.                                     *
   3  *                                                                           *
   4  * Gfxprim is free software; you can redistribute it and/or                  *
   5  * modify it under the terms of the GNU Lesser General Public                *
   6  * License as published by the Free Software Foundation; either              *
   7  * version 2.1 of the License, or (at your option) any later version.        *
   8  *                                                                           *
   9  * Gfxprim is distributed in the hope that it will be useful,                *
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of            *
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU         *
  12  * Lesser General Public License for more details.                           *
  13  *                                                                           *
  14  * You should have received a copy of the GNU Lesser General Public          *
  15  * License along with gfxprim; if not, write to the Free Software            *
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor,                        *
  17  * Boston, MA  02110-1301  USA                                               *
  18  *                                                                           *
  19  * Copyright (C) 2009-2012 Cyril Hrubis <metan@ucw.cz>                       *
  20  *                                                                           *
  21  *****************************************************************************/
  22
  23  /*
  24
  25    This header contains cubic resampling function aproximation.
  26
  27   */
  28
  29 #ifndef FILTERS_GP_CUBIC_H
  30 #define FILTERS_GP_CUBIC_H
  31
  32 #define Ap 0.5
  33
  34 static inline float cubic_float(float x)
  35 {
  36         if (x < 0)
  37                 x = -x;
  38
  39         if (x < 1)
  40                 return (2 - Ap)*x*x*x + (Ap - 3)*x*x + 1;
  41
  42         if (x < 2)
  43                 return -Ap*x*x*x + 5*Ap*x*x - 8*Ap*x + 4*Ap;
  44
  45         return 0;
  46 }
  47
  48 #include <stdint.h>
  49
  50 /* Defined in GP_Cubic.gen.c */
  51 extern int16_t GP_CubicTable[];
  52
  53 /*
  54  * Fixed point version of above.
  55  *
  56  * The input and output are expected in 24.8 fixed point format
  57  */
  58 static inline int cubic_int(int x)
  59 {
  60         if (x < 0)
  61                 x = -x;
  62
  63         if (x >= 2048)
  64                 return 0;
  65
  66         return GP_CubicTable[x];
  67 }
  68
  69 #endif /* FILTERS_GP_CUBIC_H */