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