[libcamera-devel] [PATCH 3/6] libcamera: color_space: Add fromString() function
Umang Jain
umang.jain at ideasonboard.com
Thu Aug 25 15:19:53 CEST 2022
Hi Laurent,
On 8/25/22 3:02 AM, Laurent Pinchart wrote:
> 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.
Thank you!
>>
>> 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.
Oh, so we can't really align with gstreamer using the colon(':') because
it would split awkwardly with utils::split(str, ":") I think
ColorSpace::Primaries::Rec709:ColorSpace::TransferFunction::Rec709:ColorSpace::YcbcrEncoding::Rec709:ColorSpace::Range::Full
In that case, I think "/" is our best choice. Second best I think will
be "|"
I saw a few Colorspace::toString() randomly on the internet, but none
were structural. They were mostly just meant to print it out for logs
(and not treating as string input).
I also saw DRM also has colorspaces but haven't came across a helper
like we need. I am not sure if it's worth to look further! "/" is
already a good starting point, given our requirements.
> By the way, the '/'-separated format comes from toString(). If we want
> to change it, we should update the toString() function as well.
Ack.
>
>>>> 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
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