SSIM.h

#ifndef MTF_SSIM_H
#define MTF_SSIM_H

#include "AppearanceModel.h"

_MTF_BEGIN_NAMESPACE

struct SSIMParams : AMParams{
    double k1, k2;

    SSIMParams(const AMParams *am_params,
        double _k1, double _k2);
    SSIMParams(const SSIMParams *params = nullptr);
};

struct SSIMDist : AMDist{
    typedef double ElementType;
    typedef double ResultType;
    SSIMDist(const string &_name, const double _c1, const double _c2) :
        AMDist(_name), c1(_c1), c2(_c2){}
    double operator()(const double* a, const double* b,
        size_t size, double worst_dist = -1) const override;
private:
    const double c1, c2;
};


// Structural Similarity
class SSIM : public AppearanceModel{
public:
    typedef SSIMParams ParamType;
    typedef SSIMDist DistType;

    SSIM(const ParamType *ssim_params = nullptr, const int _n_channels = 1);

    double getLikelihood() const override;

    //-------------------------------initialize functions------------------------------------//
    void initializeSimilarity() override;
    void initializeGrad() override;
    void initializeHess() override{ hess.resize(patch_size); }

    //-----------------------------------------------------------------------------------//
    //-------------------------------update functions------------------------------------//
    //-----------------------------------------------------------------------------------//
    void updateSimilarity(bool prereq_only = true) override;
    void updateInitGrad() override;
    // nothing is done here since curr_grad is same as and shares memory with  curr_pix_diff
    void updateCurrGrad() override;

    void cmptInitHessian(MatrixXd &init_hessian, const MatrixXd &init_pix_jacobian) override;
    void cmptCurrHessian(MatrixXd &curr_hessian, const MatrixXd &curr_pix_jacobian) override;

    void cmptInitHessian(MatrixXd &init_hessian, const MatrixXd &init_pix_jacobian,
        const MatrixXd &init_pix_hessian) override;
    void cmptCurrHessian(MatrixXd &curr_hessian, const MatrixXd &curr_pix_jacobian,
        const MatrixXd &curr_pix_hessian) override;

    void cmptSelfHessian(MatrixXd &self_hessian, const MatrixXd &curr_pix_jacobian) override;
    void cmptSelfHessian(MatrixXd &self_hessian, const MatrixXd &curr_pix_jacobian,
        const MatrixXd &curr_pix_hessian) override{
        cmptSelfHessian(self_hessian, curr_pix_jacobian);
    }

    /*Support for FLANN library*/
    const DistType* getDistFunc() override{
        return new DistType(name, c1, c2);
    }
    void updateDistFeat(double* feat_addr) override;
    void initializeDistFeat() override;
    void updateDistFeat() override;
    const double* getDistFeat() override{ return curr_feat_vec.data(); }
    unsigned int getDistFeatSize() override;

protected:
    ParamType params;

    double init_pix_mean, init_pix_var, init_pix_mean2;
    double curr_pix_mean, curr_pix_var, curr_pix_mean2;

    double c1, c2;
    double a, b, c, d;
    double cross_pix_var;
    double cd;

    VectorXd hess;
    VectorXd init_pix_vals_cntr, curr_pix_vals_cntr;

    RowVectorXd init_grad_vec, curr_grad_vec;
    double init_grad_scal, curr_grad_scal;

    VectorXd curr_feat_vec;
};

_MTF_END_NAMESPACE

#endif