agg_gamma_lut.h

来自「这是VCF框架的代码」· C头文件 代码 · 共 122 行

//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software 
// is granted provided this copyright notice appears in all copies. 
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: [e-mail]
//          [e-mail]
//          http://www.antigrain.com
//----------------------------------------------------------------------------

#ifndef AGG_GAMMA_LUT_INCLUDED
#define AGG_GAMMA_LUT_INCLUDED

#include <math.h>
#include "agg_basics.h"

namespace agg
{
    template<class LoResT=int8u, 
             class HiResT=int8u, 
             unsigned GammaShift=8, 
             unsigned HiResShift=8> class gamma_lut
    {
    public:
        typedef gamma_lut<LoResT, HiResT, GammaShift, HiResShift> self_type;

        enum gamma_scale_e
        {
            gamma_shift = GammaShift,
            gamma_size  = 1 << gamma_shift,
            gamma_mask  = gamma_size - 1
        };

        enum hi_res_scale_e
        {
            hi_res_shift = HiResShift,
            hi_res_size  = 1 << hi_res_shift,
            hi_res_mask  = hi_res_size - 1
        };

        ~gamma_lut()
        {
            delete [] m_inv_gamma;
            delete [] m_dir_gamma;
        }

        gamma_lut() : 
            m_gamma(1.0), 
            m_dir_gamma(new HiResT[gamma_size]),
            m_inv_gamma(new LoResT[hi_res_size])
        {
            unsigned i;
            for(i = 0; i < gamma_size; i++)
            {
                m_dir_gamma[i] = HiResT(i << (hi_res_shift - gamma_shift));
            }

            for(i = 0; i < hi_res_size; i++)
            {
                m_inv_gamma[i] = LoResT(i >> (hi_res_shift - gamma_shift));
            }
        }

        gamma_lut(double g) :
            m_gamma(1.0), 
            m_dir_gamma(new HiResT[gamma_size]),
            m_inv_gamma(new LoResT[hi_res_size])
        {
            gamma(g);
        }

        void gamma(double g) 
        {
            m_gamma = g;

            unsigned i;
            for(i = 0; i < gamma_size; i++)
            {
                m_dir_gamma[i] = (HiResT)
                    uround(pow(i / double(gamma_mask), m_gamma) * double(hi_res_mask));
            }

            double inv_g = 1.0 / g;
            for(i = 0; i < hi_res_size; i++)
            {
                m_inv_gamma[i] = (LoResT)
                    uround(pow(i / double(hi_res_mask), inv_g) * double(gamma_mask));
            }
        }

        double gamma() const
        {
            return m_gamma;
        }

        HiResT dir(LoResT v) const 
        { 
            return m_dir_gamma[unsigned(v)]; 
        }

        LoResT inv(HiResT v) const 
        { 
            return m_inv_gamma[unsigned(v)];
        }

    private:
        gamma_lut(const self_type&);
        const self_type& operator = (const self_type&);

        double m_gamma;
        HiResT* m_dir_gamma;
        LoResT* m_inv_gamma;
    };
}

#endif