mapnik/include/mapnik/gamma.hpp

/*****************************************************************************
 * 
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2006 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

//$Id: gamma.hpp 39 2005-04-10 20:39:53Z pavlenko $

#ifndef GAMMA_HPP
#define GAMMA_HPP

#include <cmath>

namespace mapnik 
{
    struct MAPNIK_DECL gamma
    {
        unsigned char g2l[256];
        unsigned char l2g[256];
        gamma(double gamma=2.0)
        {
            int result;
            for (int i=0;i< 256;i++)
            {
               result=(int)(std::pow(i/255.0,gamma) * 255.0 + 0.5);
               g2l[i]=(unsigned char)result;
            }
            for (int i = 0; i < 256; i++)
            {
               result = (int)(std::pow(i/255.0, 1/gamma) * 255.0 + 0.5);
               l2g[i] = (unsigned char)result;
            }
        }
    };
}

#endif  //GAMMA_HPP