color_conv_xyz_to_logluv.hpp

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/*

PICCANTE
The hottest HDR imaging library!
http://vcg.isti.cnr.it/piccante

Copyright (C) 2014
Visual Computing Laboratory - ISTI CNR
http://vcg.isti.cnr.it
First author: Francesco Banterle

This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/.

*/

#ifndef PIC_COLORS_COLOR_CONV_XYZ_TO_LOGLUV_HPP
#define PIC_COLORS_COLOR_CONV_XYZ_TO_LOGLUV_HPP

#include "../colors/color_conv.hpp"

namespace pic {

class ColorConvXYZtoLogLuv: public ColorConv
{
protected:
    float epsilon;

public:

    ColorConvXYZtoLogLuv()
    {
        linear = false;
        epsilon = 1.0f;
    }

    void direct(float *colIn, float *colOut)
    {

        colOut[0] = logf(colIn[1] + epsilon);

        float norm = colIn[0] + colIn[1] + colIn[2];
        float x = colIn[0] / norm;
        float y = colIn[1] / norm;

        float norm_uv = -2.0f * x + 12.0f * y + 3.0f;
        float u_prime =  4.0f * x / norm_uv;
        float v_prime =  9.0f * y / norm_uv;

        colOut[1] = u_prime;
        colOut[2] = v_prime;
    }

    void inverse(float *colIn, float *colOut)
    {
        float norm = 6.0f * colIn[1] - 16.0f * colIn[2] + 12.0f;

        float x = 9.0f * colIn[1] / norm;
        float y = 4.0f * colIn[2] / norm;
        float z = 1.0f - x - y;

        float Y = MAX(expf(colIn[0]) - epsilon, 0.0f);
        norm = Y / y;

        colOut[0] = x * norm;
        colOut[1] = Y;
        colOut[2] = z * norm;
    }
};

} // end namespace pic

#endif /* PIC_COLORS_COLOR_SPACE_LOGLUV_HPP */