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127 lines
4.3 KiB
127 lines
4.3 KiB
/////////////////////////////////////////////////////////////////////////// |
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// |
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// Copyright (c) 2003, Industrial Light & Magic, a division of Lucas |
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// Digital Ltd. LLC |
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// |
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// All rights reserved. |
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// |
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// Redistribution and use in source and binary forms, with or without |
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// modification, are permitted provided that the following conditions are |
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// met: |
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// * Redistributions of source code must retain the above copyright |
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// notice, this list of conditions and the following disclaimer. |
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// * Redistributions in binary form must reproduce the above |
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// copyright notice, this list of conditions and the following disclaimer |
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// in the documentation and/or other materials provided with the |
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// distribution. |
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// * Neither the name of Industrial Light & Magic nor the names of |
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// its contributors may be used to endorse or promote products derived |
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// from this software without specific prior written permission. |
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// |
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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// |
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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 "ImathVec.h" |
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#include "ImathMatrix.h" |
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namespace Imf { |
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struct Chromaticities |
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{ |
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Imath::V2f red; |
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Imath::V2f green; |
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Imath::V2f blue; |
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Imath::V2f white; |
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Chromaticities (const Imath::V2f &red = Imath::V2f (0.6400f, 0.3300f), |
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const Imath::V2f &green = Imath::V2f (0.3000f, 0.6000f), |
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const Imath::V2f &blue = Imath::V2f (0.1500f, 0.0600f), |
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const Imath::V2f &white = Imath::V2f (0.3127f, 0.3290f)); |
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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.red.x |
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// Yg / (Xg + Yg + Zg) == c.red.y |
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// |
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// Xb / (Xb + Yb + Zb) == c.red.x |
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// Yb / (Xb + Yb + Zb) == c.red.y |
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// |
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// Xw / (Xw + Yw + Zw) == c.red.x |
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// Yw / (Xw + Yw + Zw) == c.red.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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// YYZtoRGB(c,Y) returns RGBtoXYZ(c,Y).inverse(). |
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// |
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// Warning: |
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// |
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// It would seem that RGBtoXYZ() and XYZtoRGB() are all you need |
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// to convert RGB values with one set of primary and white point |
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// chromaticities into perceptually equivalent RGB values with |
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// different primary and white point chromaticities: |
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// |
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// M44f M = RGBtoXYZ (chromaticities1, Y1) * |
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// XYZtoRGB (chromaticities2, Y2); |
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// |
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// However, this simple conversion does not account for white point |
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// adaptation, and produces undesirable results. The proper thing |
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// to do is to perform a Bradford or a von Kries transform, which |
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// moves the white point of the original color space to the white |
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// point of the destination color space, dragging other colors with |
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// it in a sensible fashion. |
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// |
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Imath::M44f RGBtoXYZ (const Chromaticities chroma, float Y); |
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Imath::M44f XYZtoRGB (const Chromaticities chroma, float Y); |
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} // namespace Imf |
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#endif
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