// -------------------------------------------------------------------------
// @author Leonardo Florez-Valencia (florez-l@javeriana.edu.co)
// -------------------------------------------------------------------------

#ifndef __CPEXTENSIONS__ALGORITHMS__RGBTOYPBPRFUNCTION__H__
#define __CPEXTENSIONS__ALGORITHMS__RGBTOYPBPRFUNCTION__H__

#include <cmath>
#include <limits>
#include <vnl/vnl_math.h>
#include <vnl/vnl_matrix.h>

#include <itkRGBPixel.h>
#include <itkMatrix.h>
#include <itkVector.h>

namespace cpExtensions
{
  namespace Algorithms
  {
    /**
     */
    template< class P >
    struct RGBToYPbPrFunction
    {
      typedef RGBToYPbPrFunction    Self;
      typedef P                     TOutPixel;
      typedef typename P::ValueType TValue;

      template< class Tr, class Tg, class Tb >
      P operator()( const Tr& r, const Tg& g, const Tb& b ) const
        {
          static const double M[] =
            {
              double(  0.2990 ), double(  0.5870 ), double(  0.1140 ),
              double( -0.1687 ), double( -0.3313 ), double(  0.5000 ),
              double(  0.5000 ), double( -0.4187 ), double( -0.0813 )
            };
          static const vnl_matrix< double > vM( M, 3, 3 );
          static const itk::Matrix< double, 3, 3 > iM( vM );

          itk::Vector< double, 3 > rgb;
          rgb[ 0 ] = double( r );
          rgb[ 1 ] = double( b );
          rgb[ 2 ] = double( g );
          rgb = iM * rgb;

          P out;
          out[ 0 ] = TValue( rgb[ 0 ] );
          out[ 1 ] = TValue( rgb[ 1 ] );
          out[ 2 ] = TValue( rgb[ 2 ] );
          return( out );
        }

      template< class C >
      TOutPixel operator()( const itk::RGBPixel< C >& rgb ) const
        {
          return(
            this->operator()(
              rgb.GetRed( ), rgb.GetGreen( ), rgb.GetBlue( )
              )
            );
        }
    };

  } // ecapseman

} // ecapseman

#endif // __CPEXTENSIONS__ALGORITHMS__RGBTOYPBPRFUNCTION__H__

// eof - $RCSfile$