108 lines
2.9 KiB
C
108 lines
2.9 KiB
C
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//
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// SPDX-License-Identifier: BSD-3-Clause
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// Copyright (c) Contributors to the OpenEXR Project.
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//
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#ifndef INCLUDED_IMF_CHROMATICITIES_H
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#define INCLUDED_IMF_CHROMATICITIES_H
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//-----------------------------------------------------------------------------
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//
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// CIE (x,y) chromaticities, and conversions between
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// RGB tiples and CIE XYZ tristimulus values.
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//
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//-----------------------------------------------------------------------------
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#include "ImfExport.h"
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#include "ImfNamespace.h"
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#include "ImathMatrix.h"
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#include "ImathVec.h"
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OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER
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struct IMF_EXPORT_TYPE Chromaticities
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{
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//-----------------------------------------------
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// The CIE x and y coordinates of the RGB triples
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// (1,0,0), (0,1,0), (0,0,1) and (1,1,1).
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//-----------------------------------------------
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IMATH_NAMESPACE::V2f red;
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IMATH_NAMESPACE::V2f green;
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IMATH_NAMESPACE::V2f blue;
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IMATH_NAMESPACE::V2f white;
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//--------------------------------------------
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// Default constructor produces chromaticities
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// according to Rec. ITU-R BT.709-3
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//--------------------------------------------
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IMF_EXPORT
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Chromaticities (
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const IMATH_NAMESPACE::V2f& red =
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IMATH_NAMESPACE::V2f (0.6400f, 0.3300f),
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const IMATH_NAMESPACE::V2f& green =
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IMATH_NAMESPACE::V2f (0.3000f, 0.6000f),
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const IMATH_NAMESPACE::V2f& blue =
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IMATH_NAMESPACE::V2f (0.1500f, 0.0600f),
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const IMATH_NAMESPACE::V2f& white =
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IMATH_NAMESPACE::V2f (0.3127f, 0.3290f));
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//---------
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// Equality
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//---------
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IMF_EXPORT
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bool operator== (const Chromaticities& v) const;
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IMF_EXPORT
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bool operator!= (const Chromaticities& v) const;
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};
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//
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// Conversions between RGB and CIE XYZ
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//
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// RGB to XYZ:
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//
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// Given a set of chromaticities, c, and the luminance, Y, of the RGB
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// triple (1,1,1), or "white", RGBtoXYZ(c,Y) computes a matrix, M, so
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// that multiplying an RGB value, v, with M produces an equivalent
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// XYZ value, w. (w == v * M)
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//
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// If we define that
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//
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// (Xr, Yr, Zr) == (1, 0, 0) * M
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// (Xg, Yg, Zg) == (0, 1, 0) * M
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// (Xb, Yb, Zb) == (0, 0, 1) * M
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// (Xw, Yw, Zw) == (1, 1, 1) * M,
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//
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// then the following statements are true:
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//
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// Xr / (Xr + Yr + Zr) == c.red.x
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// Yr / (Xr + Yr + Zr) == c.red.y
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//
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// Xg / (Xg + Yg + Zg) == c.green.x
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// Yg / (Xg + Yg + Zg) == c.green.y
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//
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// Xb / (Xb + Yb + Zb) == c.blue.x
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// Yb / (Xb + Yb + Zb) == c.blue.y
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//
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// Xw / (Xw + Yw + Zw) == c.white.x
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// Yw / (Xw + Yw + Zw) == c.white.y
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//
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// Yw == Y.
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//
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// XYZ to RGB:
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//
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// XYZtoRGB(c,Y) returns RGBtoXYZ(c,Y).inverse().
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//
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IMF_EXPORT IMATH_NAMESPACE::M44f
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RGBtoXYZ (const Chromaticities& chroma, float Y);
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IMF_EXPORT IMATH_NAMESPACE::M44f
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XYZtoRGB (const Chromaticities& chroma, float Y);
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OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT
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#endif
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