//

// SPDX-License-Identifier: BSD-3-Clause

// Copyright (c) Contributors to the OpenEXR Project.

//

//-----------------------------------------------------------------------------

//

//  CIE (x,y) chromaticities, and conversions between

//  RGB triples and CIE XYZ tristimulus values.

//

//-----------------------------------------------------------------------------

#include "ImfNamespace.h"

#include "ImfChromaticities.h"

#include <string.h>

#include <float.h>

#include <stdexcept>

#if defined(_MSC_VER)

// suppress warning about non-exported base classes

#    pragma warning(disable : 4251)

#endif

OPENEXR_IMF_INTERNAL_NAMESPACE_SOURCE_ENTER

Chromaticities::Chromaticities (

    const IMATH_NAMESPACE::V2f& red,

    const IMATH_NAMESPACE::V2f& green,

    const IMATH_NAMESPACE::V2f& blue,

    const IMATH_NAMESPACE::V2f& white)

    : red (red), green (green), blue (blue), white (white)

{

    // empty

}

bool

Chromaticities::operator== (const Chromaticities& c) const

{

    return red == c.red && green == c.green && blue == c.blue &&

           white == c.white;

}

bool

Chromaticities::operator!= (const Chromaticities& c) const

{

    return red != c.red || green != c.green || blue != c.blue ||

           white != c.white;

}

IMATH_NAMESPACE::M44f

RGBtoXYZ (const Chromaticities& chroma, float Y)

{

    //

    // For an explanation of how the color conversion matrix is derived,

    // see Roy Hall, "Illumination and Color in Computer Generated Imagery",

    // Springer-Verlag, 1989, chapter 3, "Perceptual Response"; and

    // Charles A. Poynton, "A Technical Introduction to Digital Video",

    // John Wiley & Sons, 1996, chapter 7, "Color science for video".

    //

    //

    // X and Z values of RGB value (1, 1, 1), or "white"

    //

    // prevent a division that rounds to zero

    if (std::abs (chroma.white.y) <= 1.f &&

        std::abs (chroma.white.x * Y) >= std::abs (chroma.white.y) * FLT_MAX)

    {

        throw std::invalid_argument (

            "Bad chromaticities: white.y cannot be zero");

    }

    float X = chroma.white.x * Y / chroma.white.y;

    float Z = (1 - chroma.white.x - chroma.white.y) * Y / chroma.white.y;

    //

    // Scale factors for matrix rows, compute numerators and common denominator

    //

    float d = chroma.red.x * (chroma.blue.y - chroma.green.y) +

              chroma.blue.x * (chroma.green.y - chroma.red.y) +

              chroma.green.x * (chroma.red.y - chroma.blue.y);

    float SrN =

        (X * (chroma.blue.y - chroma.green.y) -

         chroma.green.x * (Y * (chroma.blue.y - 1) + chroma.blue.y * (X + Z)) +

         chroma.blue.x * (Y * (chroma.green.y - 1) + chroma.green.y * (X + Z)));

    float SgN =

        (X * (chroma.red.y - chroma.blue.y) +

         chroma.red.x * (Y * (chroma.blue.y - 1) + chroma.blue.y * (X + Z)) -

         chroma.blue.x * (Y * (chroma.red.y - 1) + chroma.red.y * (X + Z)));

    float SbN =

        (X * (chroma.green.y - chroma.red.y) -

         chroma.red.x * (Y * (chroma.green.y - 1) + chroma.green.y * (X + Z)) +

         chroma.green.x * (Y * (chroma.red.y - 1) + chroma.red.y * (X + Z)));

    if (std::abs (d) < 1.f && (std::abs (SrN) >= std::abs (d) * FLT_MAX ||

                               std::abs (SgN) >= std::abs (d) * FLT_MAX ||

                               std::abs (SbN) >= std::abs (d) * FLT_MAX))

    {

        // cannot generate matrix if all RGB primaries have the same y value

        // or if they all have the an x value of zero

        // in both cases, the primaries are colinear, which makes them unusable

        throw std::invalid_argument (

            "Bad chromaticities: RGBtoXYZ matrix is degenerate");

    }

    float Sr = SrN / d;

    float Sg = SgN / d;

    float Sb = SbN / d;

    //

    // Assemble the matrix

    //

    IMATH_NAMESPACE::M44f M;

    M[0][0] = Sr * chroma.red.x;

    M[0][1] = Sr * chroma.red.y;

    M[0][2] = Sr * (1 - chroma.red.x - chroma.red.y);

    M[1][0] = Sg * chroma.green.x;

    M[1][1] = Sg * chroma.green.y;

    M[1][2] = Sg * (1 - chroma.green.x - chroma.green.y);

    M[2][0] = Sb * chroma.blue.x;

    M[2][1] = Sb * chroma.blue.y;

    M[2][2] = Sb * (1 - chroma.blue.x - chroma.blue.y);

    return M;

}

IMATH_NAMESPACE::M44f

XYZtoRGB (const Chromaticities& chroma, float Y)

{

    return RGBtoXYZ (chroma, Y).inverse ();

}

OPENEXR_IMF_INTERNAL_NAMESPACE_SOURCE_EXIT