include/interpolation.h

   1 /*
   2  * interpolation.h - fast implementations of several interpolation-algorithms
   3  *
   4  * Copyright (c) 2004-2005 Tobias Doerffel <tobydox/at/users.sourceforge.net>
   5  *
   6  * This file is part of Linux MultiMedia Studio - http://lmms.sourceforge.net
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2 of the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public
  19  * License along with this program (see COPYING); if not, write to the
  20  * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  21  * Boston, MA 02110-1301 USA.
  22  *
  23  */
  24
  25
  26 #ifndef _INTERPOLATION_H
  27 #define _INTERPOLATION_H
  28
  29 #ifndef __USE_XOPEN
  30 #define __USE_XOPEN
  31 #endif
  32
  33 #include <math.h>
  34 #include "lmms_constants.h"
  35
  36 inline float hermiteInterpolate( float x0, float x1, float x2, float x3,
  37                                                                 float frac_pos )
  38 {
  39         const float frsq = frac_pos*frac_pos;
  40         const float frsq2 = 2*frsq;
  41         return( ( (x2-x0) *0.5f ) * ( frac_pos * (frsq+1) -frsq2 ) +
  42                                 ( frsq2*frac_pos - 3*frsq ) * ( x1-x2 ) +
  43                         frsq2 * (frac_pos-1) * ( ( x3-x1 ) * 0.25f ) + x1 );
  44
  45 /*
  46    const float frsq     = frac_pos*frac_pos;
  47    //const float frsq2  = 2*frsq;
  48    frac_pos *= 0.5;
  49    const float frcu     = frsq*frac_pos;
  50    return (
  51
  52    (frcu - frsq + frac_pos) * ((x2 - x0)) +
  53
  54    (4*frcu - 3*frsq) * (x1 - x2)
  55    //frsq*(2*frac_pos-3) * (x1 - x2)
  56
  57    + (frcu - 0.5*frsq)*((x3 - x1))
  58
  59    + x1
  60
  61    );
  62 */
  63 }
  64
  65
  66
  67 inline float cubicInterpolate( float v0, float v1, float v2, float v3, float x )
  68 {
  69         float frsq = x*x;
  70         float frcu = frsq*v0;
  71         float t1 = v3 + 3*v1;
  72
  73         return( v1 + 0.5f * frcu + x * ( v2 - frcu * ( 1.0f/6.0f ) -
  74                 t1 * ( 1.0f/6.0f ) - v0 / 3.0f ) + frsq * x * ( t1 *
  75                 ( 1.0f/6.0f ) - 0.5f * v2 ) + frsq * ( 0.5f * v2 - v1 ) );
  76 }
  77
  78
  79
  80 inline float cosinusInterpolate( float v0, float v1, float x )
  81 {
  82         float f = cosf( x * ( F_PI_2 ) );
  83         return( v0*f + v1*( 1.0f-f ) );
  84 }
  85
  86
  87
  88 inline float linearInterpolate( float v0, float v1, float x )
  89 {
  90         return( v0*( 1.0f-x ) + v1*x );
  91 }
  92
  93
  94 #endif