git.sesse.net Git - nageru/blob - piecewise_interpolator.cpp

   1 #include "piecewise_interpolator.h"
   2
   3 #include <assert.h>
   4
   5 double PiecewiseInterpolator::fraction_to_db(double db) const
   6 {
   7         if (db >= control_points[0].fraction) {
   8                 return control_points[0].db_value;
   9         }
  10         if (db <= control_points.back().fraction) {
  11                 return control_points.back().db_value;
  12         }
  13         for (unsigned i = 1; i < control_points.size(); ++i) {
  14                 const double x0 = control_points[i].fraction;
  15                 const double x1 = control_points[i - 1].fraction;
  16                 const double y0 = control_points[i].db_value;
  17                 const double y1 = control_points[i - 1].db_value;
  18                 if (db >= x0 && db <= x1) {
  19                         const double t = (db - x0) / (x1 - x0);
  20                         return y0 + t * (y1 - y0);
  21                 }
  22         }
  23         assert(false);
  24 }
  25
  26 double PiecewiseInterpolator::db_to_fraction(double x) const
  27 {
  28         if (x >= control_points[0].db_value) {
  29                 return control_points[0].fraction;
  30         }
  31         if (x <= control_points.back().db_value) {
  32                 return control_points.back().fraction;
  33         }
  34         for (unsigned i = 1; i < control_points.size(); ++i) {
  35                 const double x0 = control_points[i].db_value;
  36                 const double x1 = control_points[i - 1].db_value;
  37                 const double y0 = control_points[i].fraction;
  38                 const double y1 = control_points[i - 1].fraction;
  39                 if (x >= x0 && x <= x1) {
  40                         const double t = (x - x0) / (x1 - x0);
  41                         return y0 + t * (y1 - y0);
  42                 }
  43         }
  44         assert(false);
  45 }
  46