gdipp_client/gamma.cpp

   1 #include "stdafx.h"
   2 #include "gamma.h"
   3 #include "gdipp_lib/scoped_rw_lock.h"
   4
   5 namespace gdipp
   6 {
   7
   8 gamma::~gamma()
   9 {
  10         for (std::map<double, BYTE *>::const_iterator iter = _gamma_ramps.begin(); iter != _gamma_ramps.end(); ++iter)
  11                 delete[] iter->second;
  12 }
  13
  14 const BYTE *gamma::get_ramp(double gamma)
  15 {
  16         std::map<double, BYTE *>::const_iterator iter = _gamma_ramps.find(gamma);
  17         if (iter == _gamma_ramps.end())
  18         {
  19                 // double-check lock
  20                 const scoped_rw_lock lock_w(scoped_rw_lock::CLIENT_GAMMA, false);
  21                 iter = _gamma_ramps.find(gamma);
  22                 if (iter == _gamma_ramps.end())
  23                         init_ramp(gamma);
  24         }
  25
  26         return _gamma_ramps[gamma];
  27 }
  28
  29 void gamma::init_ramp(double gamma)
  30 {
  31         BYTE *new_ramp = new BYTE[256];
  32         const double gamma_inv = 1 / gamma;
  33
  34         for (int i = 0; i < 256; ++i)
  35         {
  36                 double a = pow(i / 255.0, gamma);
  37                 new_ramp[i] = static_cast<BYTE>((pow(i / 255.0, gamma_inv) * 255));
  38         }
  39
  40         _gamma_ramps[gamma] = new_ramp;
  41 }
  42
  43 }