/* radiances_to_temperatures.cpp */

/*
remap
Copyright (C) 2006 Fabrice Ducos, fabrice.ducos@icare.univ-lille1.fr

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

#include <cmath>
#include "common.h"
#include "radiances_to_temperatures.h"

void convert_radiances_to_temperatures(grid_type *grid) {

  PDEBUG;

  assert(grid);
  assert(grid->content == GRID_CONTENT_RADIANCES);

  const double C1 = 1.1910E8;   /* C1 == 2.h.c^2, in W/m^2/sr/um^-4 */
  const double C2 = 1.438833E4; /* C2 == h.c/k, in um.K */

  const int nrows = grid->nrows;
  const int ncols = grid->ncols;
  const double slope = grid->slope;
  const double offset = grid->offset;
  const double lambda = grid->wavelength; /* in microns */
  data_type *data = grid->data;

  assert(lambda > 0.);

  for (int irow = 0 ; irow < nrows ; ++irow) {
    for (int icol = 0 ; icol < ncols ; ++icol) {
      double temperature;
      data_type count = data[irow * ncols + icol];
      if (count == g_data_fill_value) continue;

      const double radiance = slope*(count - offset);
      const double x = C1 / (radiance * pow(lambda, 5));
      temperature = lambda * log(1 + x);

      data[irow * ncols + icol] = static_cast<data_type>(lround(100 * temperature));
    }
  }

  grid->slope = 0.01;
  grid->offset = 0.0;
  
}