///////////////////////////////////////////////////////////////////////////

//

// Copyright (c) 2003, Industrial Light & Magic, a division of Lucas

// Digital Ltd. LLC

// 

// All rights reserved.

// 

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///////////////////////////////////////////////////////////////////////////

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

//

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

//	RGB tiples and CIE XYZ tristimulus values.

//

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

#include <ImfChromaticities.h>

#include "ImfNamespace.h"

#include <string.h>

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;

}

bool

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

{

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

}

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"

    //

    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

    //

    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 Sr = (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))) / d;

    float Sg = (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))) / d;

    float Sb = (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))) / 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