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

[Paul Elder]

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]...?

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
>