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https://github.com/librempeg/librempeg
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719a93f4e4
libavutil/color_utils contains some avpriv_ symbols that map
enum AVTransferCharacteristic values to gamma-curve approximations and
to the actual transfer functions to invert them (i.e. -> linear).
There's two issues with this:
(1) avpriv is evil and should be avoided whenever possible
(2) libavutil/csp.h exposes a public API for handling color that
already handles primaries and matricies
I don't see any reason this API has to be private, so this commit takes
the functionality from avutil/color_utils and merges it into avutil/csp
with an exposed av_ API rather than the previous avpriv_ API.
Every reference to the previous API has been updated to point to the
new one. color_utils.h has been deleted as well. This should not break
any applications as it only contained avpriv_ symbols in the first
place, so nothing in that header could be referenced by other
applications.
Signed-off-by: Leo Izen <leo.izen@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
151 lines
4.8 KiB
C
151 lines
4.8 KiB
C
/*
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* Copyright (c) 2015 Kevin Wheatley <kevin.j.wheatley@gmail.com>
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* Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com>
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* Copyright (c) 2023 Leo Izen <leo.izen@gmail.com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVUTIL_CSP_H
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#define AVUTIL_CSP_H
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#include "pixfmt.h"
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#include "rational.h"
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/**
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* @file
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* Colorspace value utility functions for libavutil.
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* @ingroup lavu_math_csp
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* @author Ronald S. Bultje <rsbultje@gmail.com>
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* @author Leo Izen <leo.izen@gmail.com>
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* @author Kevin Wheatley <kevin.j.wheatley@gmail.com>
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*/
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/**
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* @defgroup lavu_math_csp Colorspace Utility
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* @ingroup lavu_math
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* @{
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*/
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/**
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* Struct containing luma coefficients to be used for RGB to YUV/YCoCg, or similar
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* calculations.
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*/
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typedef struct AVLumaCoefficients {
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AVRational cr, cg, cb;
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} AVLumaCoefficients;
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/**
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* Struct containing chromaticity x and y values for the standard CIE 1931
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* chromaticity definition.
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*/
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typedef struct AVCIExy {
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AVRational x, y;
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} AVCIExy;
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/**
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* Struct defining the red, green, and blue primary locations in terms of CIE
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* 1931 chromaticity x and y.
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*/
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typedef struct AVPrimaryCoefficients {
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AVCIExy r, g, b;
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} AVPrimaryCoefficients;
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/**
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* Struct defining white point location in terms of CIE 1931 chromaticity x
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* and y.
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*/
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typedef AVCIExy AVWhitepointCoefficients;
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/**
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* Struct that contains both white point location and primaries location, providing
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* the complete description of a color gamut.
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*/
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typedef struct AVColorPrimariesDesc {
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AVWhitepointCoefficients wp;
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AVPrimaryCoefficients prim;
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} AVColorPrimariesDesc;
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/**
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* Function pointer representing a double -> double transfer function that performs
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* an EOTF transfer inversion. This function outputs linear light.
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*/
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typedef double (*av_csp_trc_function)(double);
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/**
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* Retrieves the Luma coefficients necessary to construct a conversion matrix
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* from an enum constant describing the colorspace.
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* @param csp An enum constant indicating YUV or similar colorspace.
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* @return The Luma coefficients associated with that colorspace, or NULL
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* if the constant is unknown to libavutil.
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*/
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const AVLumaCoefficients *av_csp_luma_coeffs_from_avcsp(enum AVColorSpace csp);
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/**
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* Retrieves a complete gamut description from an enum constant describing the
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* color primaries.
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* @param prm An enum constant indicating primaries
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* @return A description of the colorspace gamut associated with that enum
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* constant, or NULL if the constant is unknown to libavutil.
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*/
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const AVColorPrimariesDesc *av_csp_primaries_desc_from_id(enum AVColorPrimaries prm);
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/**
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* Detects which enum AVColorPrimaries constant corresponds to the given complete
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* gamut description.
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* @see enum AVColorPrimaries
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* @param prm A description of the colorspace gamut
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* @return The enum constant associated with this gamut, or
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* AVCOL_PRI_UNSPECIFIED if no clear match can be idenitified.
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*/
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enum AVColorPrimaries av_csp_primaries_id_from_desc(const AVColorPrimariesDesc *prm);
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/**
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* Determine a suitable 'gamma' value to match the supplied
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* AVColorTransferCharacteristic.
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*
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* See Apple Technical Note TN2257 (https://developer.apple.com/library/mac/technotes/tn2257/_index.html)
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*
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* This function returns the gamma exponent for the OETF. For example, sRGB is approximated
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* by gamma 2.2, not by gamma 0.45455.
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*
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* @return Will return an approximation to the simple gamma function matching
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* the supplied Transfer Characteristic, Will return 0.0 for any
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* we cannot reasonably match against.
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*/
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double av_csp_approximate_trc_gamma(enum AVColorTransferCharacteristic trc);
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/**
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* Determine the function needed to apply the given
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* AVColorTransferCharacteristic to linear input.
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*
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* The function returned should expect a nominal domain and range of [0.0-1.0]
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* values outside of this range maybe valid depending on the chosen
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* characteristic function.
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*
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* @return Will return pointer to the function matching the
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* supplied Transfer Characteristic. If unspecified will
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* return NULL:
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*/
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av_csp_trc_function av_csp_trc_func_from_id(enum AVColorTransferCharacteristic trc);
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/**
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* @}
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*/
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#endif /* AVUTIL_CSP_H */
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