ImfChromaticities.h

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//
// SPDX-License-Identifier: BSD-3-Clause
// Copyright (c) Contributors to the OpenEXR Project.
//

#ifndef INCLUDED_IMF_CHROMATICITIES_H
#define INCLUDED_IMF_CHROMATICITIES_H

//-----------------------------------------------------------------------------
//
//      CIE (x,y) chromaticities, and conversions between
//      RGB tiples and CIE XYZ tristimulus values.
//
//-----------------------------------------------------------------------------

#include "ImfExport.h"
#include "ImfNamespace.h"

#include "ImathMatrix.h"
#include "ImathVec.h"

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER

struct IMF_EXPORT_TYPE Chromaticities
{
    //-----------------------------------------------
    // The CIE x and y coordinates of the RGB triples
    // (1,0,0), (0,1,0), (0,0,1) and (1,1,1).
    //-----------------------------------------------

    IMATH_NAMESPACE::V2f red;
    IMATH_NAMESPACE::V2f green;
    IMATH_NAMESPACE::V2f blue;
    IMATH_NAMESPACE::V2f white;

    //--------------------------------------------
    // Default constructor produces chromaticities
    // according to Rec. ITU-R BT.709-3
    //--------------------------------------------

    IMF_EXPORT
    Chromaticities (
        const IMATH_NAMESPACE::V2f& red =
            IMATH_NAMESPACE::V2f (0.6400f, 0.3300f),
        const IMATH_NAMESPACE::V2f& green =
            IMATH_NAMESPACE::V2f (0.3000f, 0.6000f),
        const IMATH_NAMESPACE::V2f& blue =
            IMATH_NAMESPACE::V2f (0.1500f, 0.0600f),
        const IMATH_NAMESPACE::V2f& white =
            IMATH_NAMESPACE::V2f (0.3127f, 0.3290f));

    //---------
    // Equality
    //---------

    IMF_EXPORT
    bool operator== (const Chromaticities& v) const;
    IMF_EXPORT
    bool operator!= (const Chromaticities& v) const;
};

//
// Conversions between RGB and CIE XYZ
//
// RGB to XYZ:
//
//      Given a set of chromaticities, c, and the luminance, Y, of the RGB
//      triple (1,1,1), or "white", RGBtoXYZ(c,Y) computes a matrix, M, so
//      that multiplying an RGB value, v, with M produces an equivalent
//      XYZ value, w.  (w == v * M)
//
//      If we define that
//
//         (Xr, Yr, Zr) == (1, 0, 0) * M
//         (Xg, Yg, Zg) == (0, 1, 0) * M
//         (Xb, Yb, Zb) == (0, 0, 1) * M
//         (Xw, Yw, Zw) == (1, 1, 1) * M,
//
//      then the following statements are true:
//
//         Xr / (Xr + Yr + Zr) == c.red.x
//         Yr / (Xr + Yr + Zr) == c.red.y
//
//         Xg / (Xg + Yg + Zg) == c.green.x
//         Yg / (Xg + Yg + Zg) == c.green.y
//
//         Xb / (Xb + Yb + Zb) == c.blue.x
//         Yb / (Xb + Yb + Zb) == c.blue.y
//
//         Xw / (Xw + Yw + Zw) == c.white.x
//         Yw / (Xw + Yw + Zw) == c.white.y
//
//         Yw == Y.
//
// XYZ to RGB:
//
//      XYZtoRGB(c,Y) returns RGBtoXYZ(c,Y).inverse().
//

IMF_EXPORT IMATH_NAMESPACE::M44f
           RGBtoXYZ (const Chromaticities& chroma, float Y);
IMF_EXPORT IMATH_NAMESPACE::M44f
           XYZtoRGB (const Chromaticities& chroma, float Y);

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT

#endif