1 //
2 // SPDX-License-Identifier: BSD-3-Clause
3 // Copyright (c) Contributors to the OpenEXR Project.
4 //
5 
6 #ifndef INCLUDED_IMF_CHROMATICITIES_H
7 #define INCLUDED_IMF_CHROMATICITIES_H
8 
9 //-----------------------------------------------------------------------------
10 //
11 //	CIE (x,y) chromaticities, and conversions between
12 //	RGB tiples and CIE XYZ tristimulus values.
13 //
14 //-----------------------------------------------------------------------------
15 
16 #include "ImfExport.h"
17 #include "ImfNamespace.h"
18 
19 #include "ImathMatrix.h"
20 #include "ImathVec.h"
21 
22 
23 OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER
24 
25 
26 struct IMF_EXPORT_TYPE Chromaticities
27 {
28     //-----------------------------------------------
29     // The CIE x and y coordinates of the RGB triples
30     // (1,0,0), (0,1,0), (0,0,1) and (1,1,1).
31     //-----------------------------------------------
32 
33     IMATH_NAMESPACE::V2f	red;
34     IMATH_NAMESPACE::V2f	green;
35     IMATH_NAMESPACE::V2f	blue;
36     IMATH_NAMESPACE::V2f	white;
37 
38     //--------------------------------------------
39     // Default constructor produces chromaticities
40     // according to Rec. ITU-R BT.709-3
41     //--------------------------------------------
42 
43     IMF_EXPORT
44     Chromaticities (const IMATH_NAMESPACE::V2f &red   = IMATH_NAMESPACE::V2f (0.6400f, 0.3300f),
45 		    const IMATH_NAMESPACE::V2f &green = IMATH_NAMESPACE::V2f (0.3000f, 0.6000f),
46 		    const IMATH_NAMESPACE::V2f &blue  = IMATH_NAMESPACE::V2f (0.1500f, 0.0600f),
47 		    const IMATH_NAMESPACE::V2f &white = IMATH_NAMESPACE::V2f (0.3127f, 0.3290f));
48 
49 
50     //---------
51     // Equality
52     //---------
53 
54     IMF_EXPORT
55     bool		operator == (const Chromaticities &v) const;
56     IMF_EXPORT
57     bool		operator != (const Chromaticities &v) const;
58 };
59 
60 
61 //
62 // Conversions between RGB and CIE XYZ
63 //
64 // RGB to XYZ:
65 //
66 // 	Given a set of chromaticities, c, and the luminance, Y, of the RGB
67 // 	triple (1,1,1), or "white", RGBtoXYZ(c,Y) computes a matrix, M, so
68 // 	that multiplying an RGB value, v, with M produces an equivalent
69 // 	XYZ value, w.  (w == v * M)
70 //
71 // 	If we define that
72 //
73 // 	   (Xr, Yr, Zr) == (1, 0, 0) * M
74 // 	   (Xg, Yg, Zg) == (0, 1, 0) * M
75 // 	   (Xb, Yb, Zb) == (0, 0, 1) * M
76 // 	   (Xw, Yw, Zw) == (1, 1, 1) * M,
77 //
78 // 	then the following statements are true:
79 //
80 // 	   Xr / (Xr + Yr + Zr) == c.red.x
81 // 	   Yr / (Xr + Yr + Zr) == c.red.y
82 //
83 // 	   Xg / (Xg + Yg + Zg) == c.green.x
84 // 	   Yg / (Xg + Yg + Zg) == c.green.y
85 //
86 // 	   Xb / (Xb + Yb + Zb) == c.blue.x
87 // 	   Yb / (Xb + Yb + Zb) == c.blue.y
88 //
89 // 	   Xw / (Xw + Yw + Zw) == c.white.x
90 // 	   Yw / (Xw + Yw + Zw) == c.white.y
91 //
92 // 	   Yw == Y.
93 //
94 // XYZ to RGB:
95 //
96 // 	XYZtoRGB(c,Y) returns RGBtoXYZ(c,Y).inverse().
97 //
98 
99 IMF_EXPORT IMATH_NAMESPACE::M44f    RGBtoXYZ (const Chromaticities &chroma, float Y);
100 IMF_EXPORT IMATH_NAMESPACE::M44f    XYZtoRGB (const Chromaticities &chroma, float Y);
101 
102 
103 OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT
104 
105 #endif
106