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ImfChromaticities.h

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2003, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// *       Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// *       Neither the name of Industrial Light & Magic nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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///////////////////////////////////////////////////////////////////////////


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

namespace Imf {

   
struct 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::V2f    red;
    Imath::V2f    green;
    Imath::V2f    blue;
    Imath::V2f    white;

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

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


//
// 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.red.x
//       Yg / (Xg + Yg + Zg) == c.red.y
// 
//       Xb / (Xb + Yb + Zb) == c.red.x
//       Yb / (Xb + Yb + Zb) == c.red.y
// 
//       Xw / (Xw + Yw + Zw) == c.red.x
//       Yw / (Xw + Yw + Zw) == c.red.y
// 
//       Yw == Y.
// 
// XYZ to RGB:
// 
//    YYZtoRGB(c,Y) returns RGBtoXYZ(c,Y).inverse().
// 

Imath::M44f RGBtoXYZ (const Chromaticities chroma, float Y);
Imath::M44f XYZtoRGB (const Chromaticities chroma, float Y);


} // namespace Imf

#endif

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