[PATCH v1 05/11] libipa: Add grey world AWB algorithm

[Stefan Klug]

Hi Paul,

Thank you for the review. 

On Mon, Jan 13, 2025 at 04:49:08PM -0600, Paul Elder wrote:
> On Thu, Jan 09, 2025 at 12:53:56PM +0100, Stefan Klug wrote:
> > Add the grey world algorithm that is currently used in rkisp1 to libipa.
> > No changes in functionality were made.
> > 
> > Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> > ---
> >  src/ipa/libipa/awb_grey.cpp | 114 ++++++++++++++++++++++++++++++++++++
> >  src/ipa/libipa/awb_grey.h   |  35 +++++++++++
> >  src/ipa/libipa/meson.build  |   2 +
> >  3 files changed, 151 insertions(+)
> >  create mode 100644 src/ipa/libipa/awb_grey.cpp
> >  create mode 100644 src/ipa/libipa/awb_grey.h
> > 
> > diff --git a/src/ipa/libipa/awb_grey.cpp b/src/ipa/libipa/awb_grey.cpp
> > new file mode 100644
> > index 000000000000..192a7cf3834a
> > --- /dev/null
> > +++ b/src/ipa/libipa/awb_grey.cpp
> > @@ -0,0 +1,114 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2024 Ideas on Board Oy
> > + *
> > + * Base class for bayesian AWB algorithm
> > + */
> > +
> > +#include "awb_grey.h"
> > +
> > +#include <cmath>
> > +
> > +#include <libcamera/base/log.h>
> > +#include <libcamera/control_ids.h>
> > +
> > +#include "colours.h"
> > +
> > +using namespace libcamera::controls;
> > +
> > +/**
> > + * \file awb_grey.h
> > + * \brief Implementation of a grey world AWB algorithm
> > + */
> > +
> > +namespace libcamera {
> > +
> > +LOG_DECLARE_CATEGORY(Awb)
> > +namespace ipa {
> > +
> > +/**
> > + * \class AwbGrey
> > + * \brief A Grey world auto white balance algorithm
> > + */
> > +
> > +/**
> > + * \brief Initialize the algorithm with the given tuning data
> > + * \param[in] tuningData The tuning data for the algorithm
> > + *
> > + * Load the colour temperature curve from the tuning data. If there is no tuning
> > + * data available, continue with a warning. Manual colour temperature will not
> > + * work in that case.
> > + *
> > + * \return 0 on success, a negative error code otherwise
> > + */
> > +int AwbGrey::init(const YamlObject &tuningData)
> > +{
> > +	Interpolator<Vector<double, 2>> gains;
> > +	int ret = gains.readYaml(tuningData["colourGains"], "ct", "gains");
> > +	if (ret < 0)
> > +		LOG(Awb, Warning)
> > +			<< "Failed to parse 'colourGains' "
> > +			<< "parameter from tuning file; "
> > +			<< "manual colour temperature will not work properly";
> > +	else
> > +		colourGainCurve_ = gains;
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * \brief Calculate awb data from the given statistics
> > + * \param[in] stats The statistics to use for the calculation
> > + * \param[in] lux The lux value of the scene
> > + *
> > + * Estimates the colour temperature based on the coulours::estimateCCT function.
> 
> s/coulours/colors/ -- wait no -- s/coulours/colours/
> 
> > + * The gains are calculated purely based on the RGB means provided by the \a
> > + * stats. The colour temperature is not taken into account when calculating the
> > + * gains.
> > + *
> > + * The \a lux parameter is not used in this algorithm.
> > + *
> > + * \return The awb result
> > + */
> > +AwbResult AwbGrey::calculateAwb(const AwbStats &stats, [[maybe_unused]] int lux)
> > +{
> > +	AwbResult result;
> > +	auto means = stats.getRGBMeans();
> > +	result.colourTemperature = estimateCCT(means);
> > +
> > +	/*
> > +	 * Estimate the red and blue gains to apply in a grey world. The green
> > +	 * gain is hardcoded to 1.0. Avoid divisions by zero by clamping the
> > +	 * divisor to a minimum value of 1.0.
> > +	 */
> > +	result.gains.r() = means.g() / std::max(means.r(), 1.0);
> > +	result.gains.g() = 1.0;
> > +	result.gains.b() = means.g() / std::max(means.b(), 1.0);
> > +	return result;
> > +}
> > +
> > +/**
> > + * \brief Compute white balance gains from a colour temperature
> > + * \param[in] colourTemperature The colour temperature in Kelvin
> > + *
> > + * Compute the white balance gains from a \a colourTemperature. This function
> > + * does not take any statistics into account. It simply interpolates the colour
> > + * gains configured in the colour temperature curve.
> > + *
> > + * \return The colour gains if a colour temperature curve is available,
> > + * [1, 1, 1] otherwise.
> > + */
> > +RGB<double> AwbGrey::gainsFromColourTemperature(double colourTemperature)
> > +{
> > +	if (!colourGainCurve_) {
> > +		LOG(Awb, Error) << "No gains defined";
> > +		return RGB<double>({ 1.0, 1.0, 1.0 });
> > +	}
> > +
> > +	auto gains = colourGainCurve_->getInterpolated(colourTemperature);
> > +	return { { gains[0], 1.0, gains[0] } };
> 
> Should the second gains[0] be gains[1]...?

Ouch. How did that slip through...

Thanks for spotting.

Cheers,
Stefan

> 
> Otherwise looks good to me.
> 
> 
> Paul
> 
> 
> > +}
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/awb_grey.h b/src/ipa/libipa/awb_grey.h
> > new file mode 100644
> > index 000000000000..6eda8e5498fb
> > --- /dev/null
> > +++ b/src/ipa/libipa/awb_grey.h
> > @@ -0,0 +1,35 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2024 Ideas on Board Oy
> > + *
> > + * AWB grey world algorithm
> > + */
> > +
> > +#pragma once
> > +
> > +#include "libcamera/internal/yaml_parser.h"
> > +
> > +#include "awb.h"
> > +#include "interpolator.h"
> > +#include "vector.h"
> > +
> > +namespace libcamera {
> > +
> > +namespace ipa {
> > +
> > +class AwbGrey : public AwbAlgorithm
> > +{
> > +public:
> > +	AwbGrey() = default;
> > +
> > +	int init(const YamlObject &tuningData) override;
> > +	AwbResult calculateAwb(const AwbStats &stats, int lux) override;
> > +	RGB<double> gainsFromColourTemperature(double coulourTemperature) override;
> > +
> > +private:
> > +	std::optional<Interpolator<Vector<double, 2>>> colourGainCurve_;
> > +};
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> > index 03e879c5834f..c550a6eb45b6 100644
> > --- a/src/ipa/libipa/meson.build
> > +++ b/src/ipa/libipa/meson.build
> > @@ -3,6 +3,7 @@
> >  libipa_headers = files([
> >      'agc_mean_luminance.h',
> >      'algorithm.h',
> > +    'awb_grey.h',
> >      'awb.h',
> >      'camera_sensor_helper.h',
> >      'colours.h',
> > @@ -21,6 +22,7 @@ libipa_headers = files([
> >  libipa_sources = files([
> >      'agc_mean_luminance.cpp',
> >      'algorithm.cpp',
> > +    'awb_grey.cpp',
> >      'awb.cpp',
> >      'camera_sensor_helper.cpp',
> >      'colours.cpp',
> > -- 
> > 2.43.0
> >