[libcamera-devel] [PATCH 3/6] libcamera: color_space: Add fromString() function
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Wed Aug 24 11:40:59 CEST 2022
Hi Umang,
On Wed, Aug 24, 2022 at 12:07:59PM +0530, Umang Jain wrote:
> On 8/23/22 11:13 PM, Laurent Pinchart via libcamera-devel wrote:
> > Add a ColorSpace:fromString() function to parse a string into a color
> > space. The string can either contain the name of a well-known color
> > space, or four color space components separate by a '/' character.
>
> I don't see the order of four components separated by '/' - documented
> in the codebase.
> Should we document the string order as well?
>
> '''
> The string representation of the colorspace separated by '/' is as follows:
> <Color primaries>/<Transfer function>/<Y'CbCr Encoding>/<Range>
> '''
I'll expand the documentation of the function to make this more
explicit.
I'm also wondering (warning, bikeshedding ahead) if the '/'-separated
format is the best option. GStreamer uses colons to separate the
components, and only accepts numerical values for the components in that
case. I'm not aware of (but haven't looked for) alternatives.
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>
> Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>
>
> > ---
> > include/libcamera/color_space.h | 2 +
> > src/libcamera/color_space.cpp | 149 +++++++++++++++++++++++++-------
> > 2 files changed, 121 insertions(+), 30 deletions(-)
> >
> > diff --git a/include/libcamera/color_space.h b/include/libcamera/color_space.h
> > index 8030a264c66f..f493f72d2db8 100644
> > --- a/include/libcamera/color_space.h
> > +++ b/include/libcamera/color_space.h
> > @@ -59,6 +59,8 @@ public:
> >
> > std::string toString() const;
> > static std::string toString(const std::optional<ColorSpace> &colorSpace);
> > +
> > + static std::optional<ColorSpace> fromString(const std::string &str);
> > };
> >
> > bool operator==(const ColorSpace &lhs, const ColorSpace &rhs);
> > diff --git a/src/libcamera/color_space.cpp b/src/libcamera/color_space.cpp
> > index 1b2dd2404452..5233626f5ae9 100644
> > --- a/src/libcamera/color_space.cpp
> > +++ b/src/libcamera/color_space.cpp
> > @@ -12,6 +12,9 @@
> > #include <map>
> > #include <sstream>
> > #include <utility>
> > +#include <vector>
> > +
> > +#include <libcamera/base/utils.h>
> >
> > /**
> > * \file color_space.h
> > @@ -208,6 +211,44 @@ const ColorSpace ColorSpace::Rec2020 = {
> > * \brief The pixel range used with by color space
> > */
> >
> > +namespace {
> > +
> > +const std::array<std::pair<ColorSpace, const char *>, 6> colorSpaceNames = { {
> > + { ColorSpace::Raw, "RAW" },
> > + { ColorSpace::Srgb, "sRGB" },
> > + { ColorSpace::Sycc, "sYCC" },
> > + { ColorSpace::Smpte170m, "SMPTE170M" },
> > + { ColorSpace::Rec709, "Rec709" },
> > + { ColorSpace::Rec2020, "Rec2020" },
> > +} };
> > +
> > +const std::map<ColorSpace::Primaries, std::string> primariesNames = {
> > + { ColorSpace::Primaries::Raw, "RAW" },
> > + { ColorSpace::Primaries::Smpte170m, "SMPTE170M" },
> > + { ColorSpace::Primaries::Rec709, "Rec709" },
> > + { ColorSpace::Primaries::Rec2020, "Rec2020" },
> > +};
> > +
> > +const std::map<ColorSpace::TransferFunction, std::string> transferNames = {
> > + { ColorSpace::TransferFunction::Linear, "Linear" },
> > + { ColorSpace::TransferFunction::Srgb, "sRGB" },
> > + { ColorSpace::TransferFunction::Rec709, "Rec709" },
> > +};
> > +
> > +const std::map<ColorSpace::YcbcrEncoding, std::string> encodingNames = {
> > + { ColorSpace::YcbcrEncoding::None, "None" },
> > + { ColorSpace::YcbcrEncoding::Rec601, "Rec601" },
> > + { ColorSpace::YcbcrEncoding::Rec709, "Rec709" },
> > + { ColorSpace::YcbcrEncoding::Rec2020, "Rec2020" },
> > +};
> > +
> > +const std::map<ColorSpace::Range, std::string> rangeNames = {
> > + { ColorSpace::Range::Full, "Full" },
> > + { ColorSpace::Range::Limited, "Limited" },
> > +};
> > +
> > +} /* namespace */
> > +
> > /**
> > * \brief Assemble and return a readable string representation of the
> > * ColorSpace
> > @@ -223,14 +264,6 @@ std::string ColorSpace::toString() const
> > {
> > /* Print out a brief name only for standard color spaces. */
> >
> > - static const std::array<std::pair<ColorSpace, const char *>, 6> colorSpaceNames = { {
> > - { ColorSpace::Raw, "RAW" },
> > - { ColorSpace::Srgb, "sRGB" },
> > - { ColorSpace::Sycc, "sYCC" },
> > - { 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;
> > @@ -240,28 +273,6 @@ std::string ColorSpace::toString() const
> >
> > /* Assemble a name made of the constituent fields. */
> >
> > - static const std::map<Primaries, std::string> primariesNames = {
> > - { Primaries::Raw, "RAW" },
> > - { Primaries::Smpte170m, "SMPTE170M" },
> > - { Primaries::Rec709, "Rec709" },
> > - { Primaries::Rec2020, "Rec2020" },
> > - };
> > - static const std::map<TransferFunction, std::string> transferNames = {
> > - { TransferFunction::Linear, "Linear" },
> > - { TransferFunction::Srgb, "sRGB" },
> > - { TransferFunction::Rec709, "Rec709" },
> > - };
> > - static const std::map<YcbcrEncoding, std::string> encodingNames = {
> > - { YcbcrEncoding::None, "None" },
> > - { YcbcrEncoding::Rec601, "Rec601" },
> > - { YcbcrEncoding::Rec709, "Rec709" },
> > - { YcbcrEncoding::Rec2020, "Rec2020" },
> > - };
> > - static const std::map<Range, std::string> rangeNames = {
> > - { Range::Full, "Full" },
> > - { Range::Limited, "Limited" },
> > - };
> > -
> > auto itPrimaries = primariesNames.find(primaries);
> > std::string primariesName =
> > itPrimaries == primariesNames.end() ? "Invalid" : itPrimaries->second;
> > @@ -303,6 +314,84 @@ std::string ColorSpace::toString(const std::optional<ColorSpace> &colorSpace)
> > return colorSpace->toString();
> > }
> >
> > +/**
> > + * \brief Construct a color space from a string
> > + * \param[in] str The string
> > + *
> > + * The string \a str can contain the name of a well-known color space, or be
> > + * made of the four color space components separate by a '/' character. Any
> > + * failure to parse the string, either because it doesn't match the expected
> > + * format, or because the one of the names isn't recognized, will cause this
> > + * function to return std::nullopt.
> > + *
> > + * \return The ColorSpace corresponding to the string, or std::nullopt if the
> > + * string doesn't describe a known color space
> > + */
> > +std::optional<ColorSpace> ColorSpace::fromString(const std::string &str)
> > +{
> > + /* First search for a standard color space name match. */
> > + auto itColorSpace = std::find_if(colorSpaceNames.begin(), colorSpaceNames.end(),
> > + [&str](const auto &item) {
> > + return str == item.second;
> > + });
> > + if (itColorSpace != colorSpaceNames.end())
> > + return itColorSpace->first;
> > +
> > + /*
> > + * If not found, the string must contain the four color space
> > + * components separated by a '/' character.
> > + */
> > + const auto &split = utils::split(str, "/");
> > + std::vector<std::string> components{ split.begin(), split.end() };
> > +
> > + if (components.size() != 4)
> > + return std::nullopt;
> > +
> > + ColorSpace colorSpace = ColorSpace::Raw;
> > +
> > + /* Color primaries */
> > + auto itPrimaries = std::find_if(primariesNames.begin(), primariesNames.end(),
> > + [&components](const auto &item) {
> > + return components[0] == item.second;
> > + });
> > + if (itPrimaries == primariesNames.end())
> > + return std::nullopt;
> > +
> > + colorSpace.primaries = itPrimaries->first;
> > +
> > + /* Transfer function */
> > + auto itTransfer = std::find_if(transferNames.begin(), transferNames.end(),
> > + [&components](const auto &item) {
> > + return components[1] == item.second;
> > + });
> > + if (itTransfer == transferNames.end())
> > + return std::nullopt;
> > +
> > + colorSpace.transferFunction = itTransfer->first;
> > +
> > + /* YCbCr encoding */
> > + auto itEncoding = std::find_if(encodingNames.begin(), encodingNames.end(),
> > + [&components](const auto &item) {
> > + return components[2] == item.second;
> > + });
> > + if (itEncoding == encodingNames.end())
> > + return std::nullopt;
> > +
> > + colorSpace.ycbcrEncoding = itEncoding->first;
> > +
> > + /* Quantization range */
> > + auto itRange = std::find_if(rangeNames.begin(), rangeNames.end(),
> > + [&components](const auto &item) {
> > + return components[3] == item.second;
> > + });
> > + if (itRange == rangeNames.end())
> > + return std::nullopt;
> > +
> > + colorSpace.range = itRange->first;
> > +
> > + return colorSpace;
> > +}
> > +
> > /**
> > * \brief Compare color spaces for equality
> > * \return True if the two color spaces are identical, false otherwise
--
Regards,
Laurent Pinchart
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