[libcamera-devel] [PATCH] ipa: raspberrypi: awb: Update colour temperature whenever manual gains change

[Naushir Patuck]

Hi David,

Thank you for this work.

On Thu, 27 Oct 2022 at 12:40, David Plowman via libcamera-devel <
libcamera-devel at lists.libcamera.org> wrote:

> Previously we only did this when the system starts (on the first
> switch_mode). Now we do it whenever the manual colour gains are
> updated. To facilitate this, this R/B vs. colour temperature inverse
> functions are stored persistently in the AwbConfig.
>
> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
>

It's good to be consistent with this behavior.

Reviewed-by: Naushir Patuck <naush at raspberrypi.com>



> ---
>  src/ipa/raspberrypi/controller/rpi/awb.cpp | 24 +++++++++-------------
>  src/ipa/raspberrypi/controller/rpi/awb.h   |  3 ++-
>  2 files changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/src/ipa/raspberrypi/controller/rpi/awb.cpp
> b/src/ipa/raspberrypi/controller/rpi/awb.cpp
> index 2b88c3b0..8d8ddf09 100644
> --- a/src/ipa/raspberrypi/controller/rpi/awb.cpp
> +++ b/src/ipa/raspberrypi/controller/rpi/awb.cpp
> @@ -104,6 +104,9 @@ int AwbConfig::read(const libcamera::YamlObject
> &params)
>                 ret = readCtCurve(ctR, ctB, params["ct_curve"]);
>                 if (ret)
>                         return ret;
> +               /* We will want the inverse functions of these too. */
> +               ctRInverse = ctR.inverse();
> +               ctBInverse = ctB.inverse();
>         }
>
>         if (params.contains("priors")) {
> @@ -174,7 +177,6 @@ Awb::Awb(Controller *controller)
>         asyncAbort_ = asyncStart_ = asyncStarted_ = asyncFinished_ = false;
>         mode_ = nullptr;
>         manualR_ = manualB_ = 0.0;
> -       firstSwitchMode_ = true;
>         asyncThread_ = std::thread(std::bind(&Awb::asyncFunc, this));
>  }
>
> @@ -270,27 +272,21 @@ void Awb::setManualGains(double manualR, double
> manualB)
>                 syncResults_.gainR = prevSyncResults_.gainR = manualR_;
>                 syncResults_.gainG = prevSyncResults_.gainG = 1.0;
>                 syncResults_.gainB = prevSyncResults_.gainB = manualB_;
> +               if (config_.bayes) {
> +                       /* Also estimate the best corresponding colour
> temperature from the curves. */
> +                       double ctR =
> config_.ctRInverse.eval(config_.ctRInverse.domain().clip(1 / manualR_));
> +                       double ctB =
> config_.ctBInverse.eval(config_.ctBInverse.domain().clip(1 / manualB_));
> +                       prevSyncResults_.temperatureK = (ctR + ctB) / 2;
> +                       syncResults_.temperatureK =
> prevSyncResults_.temperatureK;
> +               }
>         }
>  }
>
>  void Awb::switchMode([[maybe_unused]] CameraMode const &cameraMode,
>                      Metadata *metadata)
>  {
> -       /*
> -        * On the first mode switch we'll have no meaningful colour
> -        * temperature, so try to dead reckon one if in manual mode.
> -        */
> -       if (!isAutoEnabled() && firstSwitchMode_ && config_.bayes) {
> -               Pwl ctRInverse = config_.ctR.inverse();
> -               Pwl ctBInverse = config_.ctB.inverse();
> -               double ctR = ctRInverse.eval(ctRInverse.domain().clip(1 /
> manualR_));
> -               double ctB = ctBInverse.eval(ctBInverse.domain().clip(1 /
> manualB_));
> -               prevSyncResults_.temperatureK = (ctR + ctB) / 2;
> -               syncResults_.temperatureK = prevSyncResults_.temperatureK;
> -       }
>         /* Let other algorithms know the current white balance values. */
>         metadata->set("awb.status", prevSyncResults_);
> -       firstSwitchMode_ = false;
>  }
>
>  bool Awb::isAutoEnabled() const
> diff --git a/src/ipa/raspberrypi/controller/rpi/awb.h
> b/src/ipa/raspberrypi/controller/rpi/awb.h
> index cb4cfd1b..30acd89d 100644
> --- a/src/ipa/raspberrypi/controller/rpi/awb.h
> +++ b/src/ipa/raspberrypi/controller/rpi/awb.h
> @@ -42,6 +42,8 @@ struct AwbConfig {
>         bool fast; /* "fast" mode uses a 16x16 rather than 32x32 grid */
>         Pwl ctR; /* function maps CT to r (= R/G) */
>         Pwl ctB; /* function maps CT to b (= B/G) */
> +       Pwl ctRInverse; /* inverse of ctR */
> +       Pwl ctBInverse; /* inverse of ctB */
>         /* table of illuminant priors at different lux levels */
>         std::vector<AwbPrior> priors;
>         /* AWB "modes" (determines the search range) */
> @@ -168,7 +170,6 @@ private:
>         double manualR_;
>         /* manual b setting */
>         double manualB_;
> -       bool firstSwitchMode_; /* is this the first call to SwitchMode? */
>  };
>
>  static inline Awb::RGB operator+(Awb::RGB const &a, Awb::RGB const &b)
> --
> 2.30.2
>
>
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