[PATCH v2] ipa: libipa: Change constraint Y target to piecewise linear function

[Paul Elder]

On Thu, May 30, 2024 at 04:33:22AM +0900, Paul Elder wrote:
> Change the constraint luminance target from a scalar value to a
> piecewise linear function that needs to be sampled by the estimated lux
> value.
> 
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> 
> ---

I forgot to mention that this patch also depends on v3 of the series
"ipa: Move Pwl from Raspberry Pi"


Paul

> Changes in v2:
> - s/FPoint/PointF/
> - construct default Pwl with *two* points so that it actually constructs
>   properly
> ---
>  src/ipa/libipa/agc_mean_luminance.cpp | 15 +++++++++------
>  src/ipa/libipa/agc_mean_luminance.h   |  4 ++--
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/src/ipa/libipa/agc_mean_luminance.cpp b/src/ipa/libipa/agc_mean_luminance.cpp
> index 5b79d5d59..5eaa86c82 100644
> --- a/src/ipa/libipa/agc_mean_luminance.cpp
> +++ b/src/ipa/libipa/agc_mean_luminance.cpp
> @@ -168,8 +168,10 @@ void AgcMeanLuminance::parseConstraint(const YamlObject &modeDict, int32_t id)
>  		AgcConstraint::Bound bound = static_cast<AgcConstraint::Bound>(idx);
>  		double qLo = content["qLo"].get<double>().value_or(0.98);
>  		double qHi = content["qHi"].get<double>().value_or(1.0);
> -		double yTarget =
> -			content["yTarget"].getList<double>().value_or(std::vector<double>{ 0.5 }).at(0);
> +		Pwl yTarget;
> +		int ret = yTarget.readYaml(content["yTarget"]);
> +		if (ret < 0)
> +			yTarget = Pwl({ PointF(0, 0.5), PointF(1000, 0.5) });
>  
>  		AgcConstraint constraint = { bound, qLo, qHi, yTarget };
>  
> @@ -221,7 +223,7 @@ int AgcMeanLuminance::parseConstraintModes(const YamlObject &tuningData)
>  			AgcConstraint::Bound::lower,
>  			0.98,
>  			1.0,
> -			0.5
> +			Pwl({ PointF(0, 0.5), PointF(1000, 0.5) })
>  		};
>  
>  		constraintModes_[controls::ConstraintNormal].insert(
> @@ -471,16 +473,17 @@ double AgcMeanLuminance::estimateInitialGain(double lux) const
>   * \param[in] constraintModeIndex The index of the constraint to adhere to
>   * \param[in] hist A histogram over which to calculate inter-quantile means
>   * \param[in] gain The gain to clamp
> + * \param[in] lux The lux value at which to sample the constraint luminance target pwl
>   *
>   * \return The gain clamped within the constraint bounds
>   */
>  double AgcMeanLuminance::constraintClampGain(uint32_t constraintModeIndex,
>  					     const Histogram &hist,
> -					     double gain)
> +					     double gain, double lux)
>  {
>  	std::vector<AgcConstraint> &constraints = constraintModes_[constraintModeIndex];
>  	for (const AgcConstraint &constraint : constraints) {
> -		double newGain = constraint.yTarget * hist.bins() /
> +		double newGain = constraint.yTarget.eval(constraint.yTarget.domain().clamp(lux)) * hist.bins() /
>  				 hist.interQuantileMean(constraint.qLo, constraint.qHi);
>  
>  		if (constraint.bound == AgcConstraint::Bound::lower &&
> @@ -559,7 +562,7 @@ AgcMeanLuminance::calculateNewEv(uint32_t constraintModeIndex,
>  		exposureModeHelpers_.at(exposureModeIndex);
>  
>  	double gain = estimateInitialGain(lux);
> -	gain = constraintClampGain(constraintModeIndex, yHist, gain);
> +	gain = constraintClampGain(constraintModeIndex, yHist, gain, lux);
>  
>  	/*
>  	 * We don't check whether we're already close to the target, because
> diff --git a/src/ipa/libipa/agc_mean_luminance.h b/src/ipa/libipa/agc_mean_luminance.h
> index 6ec2a0dc9..d43f673dd 100644
> --- a/src/ipa/libipa/agc_mean_luminance.h
> +++ b/src/ipa/libipa/agc_mean_luminance.h
> @@ -38,7 +38,7 @@ public:
>  		Bound bound;
>  		double qLo;
>  		double qHi;
> -		double yTarget;
> +		Pwl yTarget;
>  	};
>  
>  	int parseTuningData(const YamlObject &tuningData);
> @@ -80,7 +80,7 @@ private:
>  	double estimateInitialGain(double lux) const;
>  	double constraintClampGain(uint32_t constraintModeIndex,
>  				   const Histogram &hist,
> -				   double gain);
> +				   double gain, double lux);
>  	utils::Duration filterExposure(utils::Duration exposureValue);
>  
>  	uint64_t frameCount_;
> -- 
> 2.39.2
>