Function gamma_curve

samples/unprocessed_raw.cpp:202–251

#define SQR(x) ((x) * (x))

void gamma_curve(unsigned short *curve)
{

  double pwr = 1.0 / 2.2;
  double ts = 0.0;
  int imax = 0xffff;
  int mode = 2;
  int i;
  double g[6], bnd[2] = {0, 0}, r;

  g[0] = pwr;
  g[1] = ts;
  g[2] = g[3] = g[4] = 0;
  bnd[g[1] >= 1] = 1;
  if (g[1] && (g[1] - 1) * (g[0] - 1) <= 0)
  {
    for (i = 0; i < 48; i++)
    {
      g[2] = (bnd[0] + bnd[1]) / 2;
      if (g[0])
        bnd[(pow(g[2] / g[1], -g[0]) - 1) / g[0] - 1 / g[2] > -1] = g[2];
      else
        bnd[g[2] / exp(1 - 1 / g[2]) < g[1]] = g[2];
    }
    g[3] = g[2] / g[1];
    if (g[0])
      g[4] = g[2] * (1 / g[0] - 1);
  }
  if (g[0])
    g[5] = 1 / (g[1] * SQR(g[3]) / 2 - g[4] * (1 - g[3]) +
                (1 - pow(g[3], 1 + g[0])) * (1 + g[4]) / (1 + g[0])) -
           1;
  else
    g[5] = 1 / (g[1] * SQR(g[3]) / 2 + 1 - g[2] - g[3] -
                g[2] * g[3] * (log(g[3]) - 1)) -
           1;
  for (i = 0; i < 0x10000; i++)
  {
    curve[i] = 0xffff;
    if ((r = (double)i / imax) < 1)
      curve[i] =
          0x10000 *
          (mode ? (r < g[3] ? r * g[1]
                            : (g[0] ? pow(r, g[0]) * (1 + g[4]) - g[4]
                                    : log(r) * g[2] + 1))
                : (r < g[2] ? r / g[1]
                            : (g[0] ? pow((r + g[4]) / (1 + g[4]), 1 / g[0])
                                    : exp((r - 1) / g[2]))));
  }
}

void tiff_set(ushort *ntag, ushort tag, ushort type, int count, int val)
{