[libcamera-devel] [PATCH v5 1/7] libcamera: Add ColorSpace class
Kieran Bingham
kieran.bingham at ideasonboard.com
Fri Nov 5 13:40:29 CET 2021
Quoting David Plowman (2021-11-04 13:57:59)
> This class represents a color space by defining its color primaries,
> YCbCr encoding, the transfer (gamma) function it uses, and whether the
> output is full or limited range.
>
> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> Reviewed-by: Naushir Patuck <naush at raspberrypi.com>
> ---
> include/libcamera/color_space.h | 88 +++++++++++
> include/libcamera/meson.build | 1 +
> src/libcamera/color_space.cpp | 257 ++++++++++++++++++++++++++++++++
> src/libcamera/meson.build | 1 +
> 4 files changed, 347 insertions(+)
> create mode 100644 include/libcamera/color_space.h
> create mode 100644 src/libcamera/color_space.cpp
>
> diff --git a/include/libcamera/color_space.h b/include/libcamera/color_space.h
> new file mode 100644
> index 00000000..2af9da31
> --- /dev/null
> +++ b/include/libcamera/color_space.h
> @@ -0,0 +1,88 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2021, Raspberry Pi (Trading) Limited
> + *
> + * color_space.h - color space definitions
> + */
> +
> +#ifndef __LIBCAMERA_COLOR_SPACE_H__
> +#define __LIBCAMERA_COLOR_SPACE_H__
> +
> +#include <string>
> +
> +namespace libcamera {
> +
> +class ColorSpace
> +{
> +public:
> + enum class Primaries : int {
> + Undefined,
> + Raw,
> + Smpte170m,
> + Rec709,
> + Rec2020,
> + };
> +
> + enum class YcbcrEncoding : int {
> + Undefined,
> + Rec601,
> + Rec709,
> + Rec2020,
> + };
> +
> + enum class TransferFunction : int {
> + Undefined,
> + Linear,
> + Srgb,
> + Rec709,
> + };
> +
> + enum class Range : int {
> + Undefined,
> + Full,
> + Limited,
> + };
> +
> + constexpr ColorSpace()
> + : ColorSpace(Primaries::Undefined, YcbcrEncoding::Undefined, TransferFunction::Undefined, Range::Undefined)
> + {
> + }
> +
> + constexpr ColorSpace(Primaries p, YcbcrEncoding e, TransferFunction t, Range r)
> + : primaries(p), ycbcrEncoding(e), transferFunction(t), range(r)
> + {
> + }
> +
> + static const ColorSpace Undefined;
> + static const ColorSpace Raw;
> + static const ColorSpace Jpeg;
> + static const ColorSpace Smpte170m;
> + static const ColorSpace Rec709;
> + static const ColorSpace Rec2020;
> +
> + Primaries primaries;
> + YcbcrEncoding ycbcrEncoding;
> + TransferFunction transferFunction;
> + Range range;
> +
> + bool isFullyDefined() const;
> +
> + const std::string toString() const;
> +};
> +
> +constexpr ColorSpace ColorSpace::Undefined = { Primaries::Undefined, YcbcrEncoding::Undefined, TransferFunction::Undefined, Range::Undefined };
> +constexpr ColorSpace ColorSpace::Raw = { Primaries::Raw, YcbcrEncoding::Rec601, TransferFunction::Linear, Range::Full };
> +constexpr ColorSpace ColorSpace::Jpeg = { Primaries::Rec709, YcbcrEncoding::Rec601, TransferFunction::Srgb, Range::Full };
> +constexpr ColorSpace ColorSpace::Smpte170m = { Primaries::Smpte170m, YcbcrEncoding::Rec601, TransferFunction::Rec709, Range::Limited };
> +constexpr ColorSpace ColorSpace::Rec709 = { Primaries::Rec709, YcbcrEncoding::Rec709, TransferFunction::Rec709, Range::Limited };
> +constexpr ColorSpace ColorSpace::Rec2020 = { Primaries::Rec2020, YcbcrEncoding::Rec2020, TransferFunction::Rec709, Range::Limited };
Is the mix between static const and constexpr correct in those? (I guess
it compiles so it's fine?)
Should the definitions be in the .cpp file ? I guess they're 'simple'
data storage but I think the usual aim is to reduce header sizes for
parsing.
Though this is the public API... perhaps theres a distinct reason for
openly declaring the colorspace definition in the header so that it is
clear to the users. So I think that makes it worthy of staying here too.
> +
> +bool operator==(const ColorSpace &lhs, const ColorSpace &rhs);
> +static inline bool operator!=(const ColorSpace &lhs, const ColorSpace &rhs)
> +{
> + return !(lhs == rhs);
> +}
> +
> +} /* namespace libcamera */
> +
> +#endif /* __LIBCAMERA_COLOR_SPACE_H__ */
> diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
> index 7155ff20..131e1740 100644
> --- a/include/libcamera/meson.build
> +++ b/include/libcamera/meson.build
> @@ -5,6 +5,7 @@ libcamera_include_dir = 'libcamera' / 'libcamera'
> libcamera_public_headers = files([
> 'camera.h',
> 'camera_manager.h',
> + 'color_space.h',
> 'compiler.h',
> 'controls.h',
> 'file_descriptor.h',
> diff --git a/src/libcamera/color_space.cpp b/src/libcamera/color_space.cpp
> new file mode 100644
> index 00000000..dfd9fa1d
> --- /dev/null
> +++ b/src/libcamera/color_space.cpp
> @@ -0,0 +1,257 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2021, Raspberry Pi (Trading) Limited
> + *
> + * color_space.cpp - color spaces.
> + */
> +
> +#include <libcamera/color_space.h>
> +
> +#include <algorithm>
> +#include <sstream>
> +#include <vector>
> +
> +/**
> + * \file color_space.h
> + * \brief Class and enums to represent color spaces
> + */
> +
> +namespace libcamera {
> +
> +/**
> + * \class ColorSpace
> + * \brief Class to describe a color space
> + *
> + * The ColorSpace class defines the color primaries, the Y'CbCr encoding,
> + * the transfer function associated with the color space, and the range
> + * (sometimes also referred to as the quantisation) of the color space.
> + *
> + * Certain combinations of these fields form well-known standard color
> + * spaces such as "JPEG" or "REC709". Applications must not request color
> + * spaces with undefined fields, but the "Undefined" value may be
> + * returned if the camera drivers decide to use a color space that is
> + * not recognised by the ColorSpace class.
> + *
> + * For more information on the specific color spaces described here, please
> + * see:
> + *
> + * <a href="https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-007.html#col-srgb">sRGB</a> and <a href="https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-007.html#col-jpeg">JPEG</a>
I think that can be wrapped to
<a href="https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-007.html#col-srgb">sRGB</a>
and <a href="https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-007.html#col-jpeg">JPEG</a>
at least.
> +>* <a href="https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-007.html#col-smpte-170m">SMPTE 170M</a>
> + * <a href="https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-007.html#col-rec709">Rec.709</a>
> + * <a href="https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-007.html#col-bt2020">Rec.2020</a>
Can we do better than v4.8? That was EOL January 2017...
I think the documentation all got shuffled around so changing /v4.8/ to
/latest/ doesn't get the right thing anymore.
Perhaps:
https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/colorspaces-defs.html
and
https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/colorspaces-details.html#col-srgb
Or use v5.15 in place of latest to lock in to more permanant version
links?
> + */
> +
> +/**
> + * \enum ColorSpace::Primaries
> + * \brief The color primaries for this color space
> + *
> + * \var ColorSpace::Primaries::Undefined
> + * \brief The color primaries are undefined
> + * \var ColorSpace::Primaries::Raw
> + * \brief These are raw colors directly from a sensor
> + * \var ColorSpace::Primaries::Smpte170m
> + * \brief SMPTE 170M color primaries
> + * \var ColorSpace::Primaries::Rec709
> + * \brief Rec.709 color primaries
> + * \var ColorSpace::Primaries::Rec2020
> + * \brief Rec.2020 color primaries
> + */
> +
> +/**
> + * \enum ColorSpace::YcbcrEncoding
> + * \brief The Y'CbCr encoding
> + *
> + * \var ColorSpace::YcbcrEncoding::Undefined
> + * \brief The Y'CbCr encoding is undefined
> + * \var ColorSpace::YcbcrEncoding::Rec601
> + * \brief Rec.601 Y'CbCr encoding
> + * \var ColorSpace::YcbcrEncoding::Rec709
> + * \brief Rec.709 Y'CbCr encoding
> + * \var ColorSpace::YcbcrEncoding::Rec2020
> + * \brief Rec.2020 Y'CbCr encoding
> + */
> +
> +/**
> + * \enum ColorSpace::TransferFunction
> + * \brief The transfer function used for this color space
> + *
> + * \var ColorSpace::TransferFunction::Undefined
> + * \brief The transfer function is not specified
> + * \var ColorSpace::TransferFunction::Linear
> + * \brief This color space uses a linear (identity) transfer function
> + * \var ColorSpace::TransferFunction::Srgb
> + * \brief sRGB transfer function
> + * \var ColorSpace::TransferFunction::Rec709
> + * \brief Rec709 transfer function
> + */
> +
> +/**
> + * \enum ColorSpace::Range
> + * \brief The range (sometimes "quantisation") for this color space
> + *
> + * \var ColorSpace::Range::Undefined
> + * \brief The range is not specified
> + * \var ColorSpace::Range::Full
> + * \brief This color space uses full range pixel values
> + * \var ColorSpace::Range::Limited
> + * \brief This color space uses limited range pixel values, being
> + * 16 to 235 for Y' and 16 to 240 for Cb and Cr (8 bits per sample)
> + * or 64 to 940 for Y' and 16 to 960 for Cb and Cr (10 bits)
> + */
> +
> +/**
> + * \fn ColorSpace::ColorSpace(Encoding e, TransferFunction t, Range r)
> + * \brief Construct a ColorSpace from explicit values
> + * \param[in] e The Y'CbCr encoding
> + * \param[in] t The transfer function for the color space
> + * \param[in] r The range of the pixel values in this color space
> + */
> +
> +/**
> + * \fn ColorSpace::ColorSpace()
> + * \brief Construct a color space with undefined encoding, transfer function
> + * and range
> + */
> +
> +/**
> + * \brief Check if all the fields of the color space are defined
> + * \return Return true if all the fields of the color space are defined,
> + * otherwise false
> + */
> +bool ColorSpace::isFullyDefined() const
> +{
> + return primaries != Primaries::Undefined &&
> + ycbcrEncoding != YcbcrEncoding::Undefined &&
> + transferFunction != TransferFunction::Undefined &&
> + range != Range::Undefined;
> +}
> +
> +/**
> + * \brief Assemble and return a readable string representation of the
> + * ColorSpace
> + * \return A string describing the ColorSpace
> + */
> +const std::string ColorSpace::toString() const
> +{
> + /* Print out a brief name only for standard color sapces. */
s/sapces/spaces/
> +
> + static const std::vector<std::pair<ColorSpace, const char *>> colorSpaceNames = {
> + { ColorSpace::Undefined, "Undefined" },
> + { ColorSpace::Raw, "Raw" },
> + { ColorSpace::Jpeg, "Jpeg" },
> + { ColorSpace::Smpte170m, "Smpte170m" },
> + { ColorSpace::Rec709, "Rec709" },
> + { ColorSpace::Rec2020, "Rec2020" },
> + };
> + auto it = std::find_if(colorSpaceNames.begin(), colorSpaceNames.end(),
> + [this](const auto &item) {
> + return *this == item.first;
> + });
> + if (it != colorSpaceNames.end())
> + return std::string(it->second);
> +
> + static const char *primariesNames[] = {
> + "Undefined",
> + "Raw",
> + "Smpte170m",
> + "Rec709",
> + "Rec2020",
> + };
> + static const char *encodingNames[] = {
> + "Undefined",
> + "Rec601",
> + "Rec709",
> + "Rec2020",
> + };
> + static const char *transferFunctionNames[] = {
> + "Undefined",
> + "Linear",
> + "Srgb",
> + "Rec709",
> + };
> + static const char *rangeNames[] = {
> + "Undefined",
> + "Full",
> + "Limited",
> + };
> +
> + std::stringstream ss;
> + ss << std::string(primariesNames[static_cast<int>(primaries)]) << "/"
> + << std::string(encodingNames[static_cast<int>(ycbcrEncoding)]) << "/"
> + << std::string(transferFunctionNames[static_cast<int>(transferFunction)]) << "/"
> + << std::string(rangeNames[static_cast<int>(range)]);
> +
> + return ss.str();
> +}
> +
> +/**
> + * \var ColorSpace::primaries
> + * \brief The color primaries
> + */
> +
> +/**
> + * \var ColorSpace::ycbcrEncoding
> + * \brief The Y'CbCr encoding
> + */
> +
> +/**
> + * \var ColorSpace::transferFunction
> + * \brief The transfer function for this color space
> + */
> +
> +/**
> + * \var ColorSpace::range
> + * \brief The pixel range used by this color space
> + */
> +
> +/**
> + * \var ColorSpace::Undefined
> + * \brief A constant representing a fully undefined color space
> + */
> +
> +/**
> + * \var ColorSpace::Raw
> + * \brief A constant representing a raw color space (from a sensor)
> + */
> +
> +/**
> + * \var ColorSpace::Jpeg
> + * \brief A constant representing the JPEG color space used for
> + * encoding JPEG images (and regarded as being the same as the sRGB
> + * color space)
> + */
> +
> +/**
> + * \var ColorSpace::Smpte170m
> + * \brief A constant representing the SMPTE170M color space
I wonder if these are a good opportunity to link to the specific
documentation from V4L2...
https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/colorspaces-details.html#col-smpte-170m
> + */
> +
> +/**
> + * \var ColorSpace::Rec709
> + * \brief A constant representing the Rec.709 color space
> + */
> +
> +/**
> + * \var ColorSpace::Rec2020
> + * \brief A constant representing the Rec.2020 color space
> + */
> +
> +/**
> + * \brief Compare color spaces for equality
> + * \return True if the two color spaces are identical, false otherwise
> + */
> +bool operator==(const ColorSpace &lhs, const ColorSpace &rhs)
> +{
> + return lhs.primaries == rhs.primaries &&
> + lhs.ycbcrEncoding == rhs.ycbcrEncoding &&
> + lhs.transferFunction == rhs.transferFunction &&
> + lhs.range == rhs.range;
> +}
> +
> +/**
> + * \fn bool operator!=(const ColorSpace &lhs, const ColorSpace &rhs)
> + * \brief Compare color spaces for inequality
> + * \return True if the two color spaces are not identical, false otherwise
> + */
> +
> +} /* namespace libcamera */
> diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> index 6727a777..e7371d20 100644
> --- a/src/libcamera/meson.build
> +++ b/src/libcamera/meson.build
> @@ -8,6 +8,7 @@ libcamera_sources = files([
> 'camera_manager.cpp',
> 'camera_sensor.cpp',
> 'camera_sensor_properties.cpp',
> + 'color_space.cpp',
> 'controls.cpp',
> 'control_serializer.cpp',
> 'control_validator.cpp',
> --
> 2.20.1
>
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