gaussian.hpp

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#ifndef _TERRY_SAMPLER_GAUSSIAN_HPP_
#define _TERRY_SAMPLER_GAUSSIAN_HPP_

#include "details.hpp"
#include <boost/math/constants/constants.hpp>

namespace terry {
using namespace boost::gil;
namespace sampler {

// from http://avisynth.org/mediawiki/Resampling#Gaussian_resampler


struct gaussian_sampler
{
        const size_t         _windowSize;
        RESAMPLING_CORE_TYPE _sigma;

        gaussian_sampler() :
                _windowSize ( 4.0 ), // size = 3.0
                _sigma      ( 1.0 )
        {
        }

        gaussian_sampler( size_t windowSize, size_t sigma ) :
                _windowSize ( windowSize + 1 ),
                _sigma      ( sigma )
        {
        }
        
        template< typename Weight >
        void operator()( const RESAMPLING_CORE_TYPE& distance, Weight& weight )
        {
                if( _sigma > -std::numeric_limits<RESAMPLING_CORE_TYPE>::epsilon() &&
                    _sigma < std::numeric_limits<RESAMPLING_CORE_TYPE>::epsilon())
                {
                        weight = 0.0;
                        return;
                }
                //weight = std::pow( 2.f, - 0.1 * _sigma * distance * distance );
                weight = 1.0 / ( _sigma * std::sqrt( 2 * boost::math::constants::pi<RESAMPLING_CORE_TYPE>() )) * std::exp( - distance * distance / ( 2 * _sigma ) ) ;
        }
};

}
}

#endif