/*
 * Copyright (C) 2005-2020 Centre National d'Etudes Spatiales (CNES)
 *
 * This file is part of Orfeo Toolbox
 *
 *     https://www.orfeo-toolbox.org/
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


#ifndef otbMuellerToReciprocalCovarianceImageFilter_h
#define otbMuellerToReciprocalCovarianceImageFilter_h

#include "otbFunctorImageFilter.h"

namespace otb
{

namespace Functor
{

/** \class MuellerToReciprocalCovarianceFunctor
 * \brief Evaluate the  MLC image from the Mueller image
 *
 * Output value are:
 * - channel #0 : \f$ 0.5*(M_{11} + M_{22} + 2*M_{12}) \f$
 * - channel #1 : \f$ 0.5*(M_{11} - M_{22}) \f$
 * - channel #2 : \f$ 0.5*(M_{11} + M_{22} - 2*M_{12}) \f$
 * - channel #3 : \f$ 0.5*(M_{13} + M_{23} + i*(M_{14}+M_{24})) \f$
 * - channel #4 : \f$ 0.5*(M_{33} - M_{44} - 2*i*M_{34}) \f$
 * - channel #5 : \f$ 0.5*(M_{13} - M_{23} - i*(M_{14}-M_{24})) \f$
 *
 * Where \f$M_{ij}\f$ are the coefficients of the input Mueller matrix.
 *
 * Input pixel must have 10 channels (one for each Mueller matrix coeffcients).
 * The order of the channels corresponds to :
 * \f$ \begin{pmatrix}
 * {channel #0 }&{channel #1 }&{channel #2 }&{channel #3 } \\
 * {channel #4 }&{channel #5 }&{channel #6 }&{channel #7 } \\
 * {channel #8 }&{channel #9 }&{channel #10}&{channel #11} \\
 * {channel #12}&{channel #13}&{channel #14}&{channel #15} \\
 * \end{pmatrix} \f$
 *
 * The output image has 6 channels : the diagonal and the upper element of the reciprocal matrix.
 * Element are stored from left to right, line by line.
 *
 * Use otb::MuellerToReciprocalCovarianceImageFilter to apply
 *
 * \ingroup Functor
 * \ingroup SARPolarimetry
 *
 * \sa MuellerToCircularPolarisationImageFilter
 * \sa MuellerToPolarisationDegreeAndPowerImageFilter
 *
 *
 * \ingroup OTBPolarimetry
 */

template <class TInput, class TOutput>
class MuellerToReciprocalCovarianceFunctor
{
public:
  typedef std::complex<double>        ComplexType;
  typedef typename TOutput::ValueType OutputValueType;

  inline void operator()(TOutput& result, const TInput& Mueller) const
  {
    // Keep the upper diagonal of the matrix
    const double M11 = static_cast<double>(Mueller[0]);
    const double M12 = static_cast<double>(Mueller[1]);
    const double M13 = static_cast<double>(Mueller[2]);
    const double M14 = static_cast<double>(Mueller[3]);
    const double M22 = static_cast<double>(Mueller[5]);
    const double M23 = static_cast<double>(Mueller[6]);
    const double M24 = static_cast<double>(Mueller[7]);
    const double M33 = static_cast<double>(Mueller[10]);
    const double M34 = static_cast<double>(Mueller[11]);
    const double M44 = static_cast<double>(Mueller[15]);


    const ComplexType A(0.5 * (M11 + M22 + 2 * M12));
    const ComplexType B(0.5 * std::sqrt(2.0) * (M13 + M23), 0.5 * std::sqrt(2.0) * (M14 + M24));
    const ComplexType C(-0.5 * (M33 + M44), -M34);
    const ComplexType E(M11 - M22, 0.0);
    const ComplexType F(0.5 * std::sqrt(2.0) * (M13 - M23), 0.5 * std::sqrt(2.0) * (M14 - M24));
    const ComplexType I(0.5 * (M11 + M22 - 2 * M12));

    result[0] = static_cast<OutputValueType>(A);
    result[1] = static_cast<OutputValueType>(B);
    result[2] = static_cast<OutputValueType>(C);
    result[3] = static_cast<OutputValueType>(E);
    result[4] = static_cast<OutputValueType>(F);
    result[5] = static_cast<OutputValueType>(I);
  }

  constexpr size_t OutputSize(...) const
  {
    // Size of the result
    return 6;
  }
};
} // namespace Functor

/**
 * \typedef MuellerToReciprocalCovarianceImageFilter
 * \brief Applies otb::Functor::MuellerToReciprocalCovarianceFunctor
 * \sa otb::Functor::MuellerToReciprocalCovarianceFunctor
 *
 * Set inputs with:
 * \code
 * SetInput<0>(inputPtr);
 * \endcode
 *
 * \ingroup OTBPolarimetry
 */
template <typename TInputImage, typename TOutputImage>
using MuellerToReciprocalCovarianceImageFilter =
    FunctorImageFilter<Functor::MuellerToReciprocalCovarianceFunctor<typename TInputImage::PixelType, typename TOutputImage::PixelType>>;


} // end namespace otb

#endif
