[libcamera-devel] [PATCH 3/6] libcamera: color_space: Add fromString() function
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Wed Aug 24 23:32:18 CEST 2022
On Wed, Aug 24, 2022 at 12:40:59PM +0300, Laurent Pinchart via libcamera-devel wrote:
> 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.
By the way, the '/'-separated format comes from toString(). If we want
to change it, we should update the toString() function as well.
> > > 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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