[v5,14/18] libcamera: software_isp: Move color handling to an algorithm module

21070 diff mbox series

After black level handling has been moved to an algorithm module, white
balance and the construction of color tables can be moved to algorithm
modules too.

This time, the moved code is split between stats processing and
parameter construction methods.  It is also split to three algorithm
modules:

- Gamma table computation.  This is actually independent of color
  handling.

- White balance computation.

- Color lookup tables construction.  While this applies the color gains
  computed by the white balance algorithm, it is not directly related to
  white balance.  We may want to modify the color lookup tables in
  future according to other parameters than just gamma and white balance
  gains.

This is the only part of the software ISP algorithms that sets the
parameters so emitting setIspParams can be moved to prepare() method.

A more natural representation of the gains (and black level) would be
floating point numbers.  This is not done here in order to minimize
changes in code movements.  It will be addressed in a followup patch.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
---
 src/ipa/simple/algorithms/awb.cpp     | 70 +++++++++++++++++++++++++++
 src/ipa/simple/algorithms/awb.h       | 38 +++++++++++++++
 src/ipa/simple/algorithms/gamma.cpp   | 64 ++++++++++++++++++++++++
 src/ipa/simple/algorithms/gamma.h     | 42 ++++++++++++++++
 src/ipa/simple/algorithms/lut.cpp     | 57 ++++++++++++++++++++++
 src/ipa/simple/algorithms/lut.h       | 37 ++++++++++++++
 src/ipa/simple/algorithms/meson.build |  3 ++
 src/ipa/simple/data/uncalibrated.yaml |  3 ++
 src/ipa/simple/ipa_context.cpp        | 30 ++++++++++++
 src/ipa/simple/ipa_context.h          | 12 +++++
 src/ipa/simple/soft_simple.cpp        | 66 ++-----------------------
 11 files changed, 360 insertions(+), 62 deletions(-)
 create mode 100644 src/ipa/simple/algorithms/awb.cpp
 create mode 100644 src/ipa/simple/algorithms/awb.h
 create mode 100644 src/ipa/simple/algorithms/gamma.cpp
 create mode 100644 src/ipa/simple/algorithms/gamma.h
 create mode 100644 src/ipa/simple/algorithms/lut.cpp
 create mode 100644 src/ipa/simple/algorithms/lut.h

Hi Milan,

Thank you for the patch.

On Fri, Aug 30, 2024 at 09:25:50AM +0200, Milan Zamazal wrote:
> After black level handling has been moved to an algorithm module, white
> balance and the construction of color tables can be moved to algorithm
> modules too.
> 
> This time, the moved code is split between stats processing and
> parameter construction methods.  It is also split to three algorithm
> modules:
> 
> - Gamma table computation.  This is actually independent of color
>   handling.
> 
> - White balance computation.
> 
> - Color lookup tables construction.  While this applies the color gains
>   computed by the white balance algorithm, it is not directly related to
>   white balance.  We may want to modify the color lookup tables in
>   future according to other parameters than just gamma and white balance
>   gains.
> 
> This is the only part of the software ISP algorithms that sets the
> parameters so emitting setIspParams can be moved to prepare() method.
> 
> A more natural representation of the gains (and black level) would be
> floating point numbers.  This is not done here in order to minimize
> changes in code movements.  It will be addressed in a followup patch.
> 
> Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
> ---
>  src/ipa/simple/algorithms/awb.cpp     | 70 +++++++++++++++++++++++++++
>  src/ipa/simple/algorithms/awb.h       | 38 +++++++++++++++
>  src/ipa/simple/algorithms/gamma.cpp   | 64 ++++++++++++++++++++++++
>  src/ipa/simple/algorithms/gamma.h     | 42 ++++++++++++++++
>  src/ipa/simple/algorithms/lut.cpp     | 57 ++++++++++++++++++++++
>  src/ipa/simple/algorithms/lut.h       | 37 ++++++++++++++
>  src/ipa/simple/algorithms/meson.build |  3 ++
>  src/ipa/simple/data/uncalibrated.yaml |  3 ++
>  src/ipa/simple/ipa_context.cpp        | 30 ++++++++++++
>  src/ipa/simple/ipa_context.h          | 12 +++++
>  src/ipa/simple/soft_simple.cpp        | 66 ++-----------------------
>  11 files changed, 360 insertions(+), 62 deletions(-)
>  create mode 100644 src/ipa/simple/algorithms/awb.cpp
>  create mode 100644 src/ipa/simple/algorithms/awb.h
>  create mode 100644 src/ipa/simple/algorithms/gamma.cpp
>  create mode 100644 src/ipa/simple/algorithms/gamma.h
>  create mode 100644 src/ipa/simple/algorithms/lut.cpp
>  create mode 100644 src/ipa/simple/algorithms/lut.h
> 
> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
> new file mode 100644
> index 00000000..4b49996a
> --- /dev/null
> +++ b/src/ipa/simple/algorithms/awb.cpp
> @@ -0,0 +1,70 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Red Hat Inc.
> + *
> + * Auto white balance
> + */
> +
> +#include "awb.h"
> +
> +#include <numeric>
> +#include <stdint.h>
> +
> +#include <libcamera/base/log.h>
> +
> +#include "simple/ipa_context.h"
> +
> +namespace libcamera {
> +
> +LOG_DEFINE_CATEGORY(IPASoftAwb)
> +
> +namespace ipa::soft::algorithms {
> +
> +int Awb::init(IPAContext &context,
> +	      [[maybe_unused]] const YamlObject &tuningData)
> +{
> +	auto &gains = context.activeState.gains;
> +	gains.red = gains.green = gains.blue = 256;
> +
> +	return 0;
> +}
> +
> +void Awb::process(IPAContext &context,
> +		  [[maybe_unused]] const uint32_t frame,
> +		  [[maybe_unused]] IPAFrameContext &frameContext,
> +		  const SwIspStats *stats,
> +		  [[maybe_unused]] ControlList &metadata)
> +{
> +	const SwIspStats::Histogram &histogram = stats->yHistogram;
> +	const uint8_t blackLevel = context.activeState.black.level;
> +
> +	/*
> +	 * Black level must be subtracted to get the correct AWB ratios, they
> +	 * would be off if they were computed from the whole brightness range
> +	 * rather than from the sensor range.
> +	 */
> +	const uint64_t nPixels = std::accumulate(
> +		histogram.begin(), histogram.end(), 0);
> +	const uint64_t offset = blackLevel * nPixels;
> +	const uint64_t sumR = stats->sumR_ - offset / 4;
> +	const uint64_t sumG = stats->sumG_ - offset / 2;
> +	const uint64_t sumB = stats->sumB_ - offset / 4;
> +
> +	/*
> +	 * Calculate red and blue gains for AWB.
> +	 * Clamp max gain at 4.0, this also avoids 0 division.
> +	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
> +	 */
> +	auto &gains = context.activeState.gains;
> +	gains.red = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
> +	gains.blue = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
> +	/* Green gain is fixed to 256 */
> +
> +	LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
> +}
> +
> +REGISTER_IPA_ALGORITHM(Awb, "Awb")
> +
> +} /* namespace ipa::soft::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/simple/algorithms/awb.h b/src/ipa/simple/algorithms/awb.h
> new file mode 100644
> index 00000000..c0b88bec
> --- /dev/null
> +++ b/src/ipa/simple/algorithms/awb.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Red Hat Inc.
> + *
> + * Auto white balance
> + */
> +
> +#pragma once
> +
> +#include <libcamera/controls.h>
> +
> +#include "libcamera/internal/software_isp/swisp_stats.h"
> +
> +#include "algorithm.h"
> +#include "ipa_context.h"

As with the previous patch, I think you can drop all the includes except
algorithm.h. Same for the other algorithms.

> +
> +namespace libcamera {
> +
> +namespace ipa::soft::algorithms {
> +
> +class Awb : public Algorithm
> +{
> +public:
> +	Awb() = default;
> +	~Awb() = default;
> +
> +	int init(IPAContext &context, const YamlObject &tuningData)
> +		override;

No need to split this on two lines. Same below.

> +	void process(IPAContext &context,
> +		     const uint32_t frame,
> +		     IPAFrameContext &frameContext,
> +		     const SwIspStats *stats,
> +		     ControlList &metadata) override;
> +};
> +
> +} /* namespace ipa::soft::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/simple/algorithms/gamma.cpp b/src/ipa/simple/algorithms/gamma.cpp
> new file mode 100644
> index 00000000..0b8ec5ee
> --- /dev/null
> +++ b/src/ipa/simple/algorithms/gamma.cpp
> @@ -0,0 +1,64 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Red Hat Inc.
> + *
> + * Gamma table construction
> + */
> +
> +#include "gamma.h"
> +
> +#include <algorithm>
> +#include <cmath>
> +#include <stdint.h>
> +
> +#include <libcamera/base/log.h>
> +
> +#include "simple/ipa_context.h"
> +
> +namespace libcamera {
> +
> +namespace ipa::soft::algorithms {
> +
> +int Gamma::init(IPAContext &context,
> +		[[maybe_unused]] const YamlObject &tuningData)
> +{
> +	/* Gamma value is fixed */
> +	context.configuration.gamma = 0.5;
> +	updateGammaTable(context);

Same question as before, does this belong to .init() ? Actually, given
that prepare() will always be called to calculate ISP parameters, do you
even need to initialize the gamme table ?

> +
> +	return 0;
> +}
> +
> +void Gamma::updateGammaTable(IPAContext &context)
> +{
> +	auto &gammaTable = context.activeState.gamma.gammaTable;
> +	auto blackLevel = context.activeState.black.level;
> +	const unsigned int blackIndex =
> +		blackLevel * IPAActiveState::kGammaLookupSize / 256;

Use gammaTable.size() instead of kGammaLookupSize.

> +	std::fill(gammaTable.begin(), gammaTable.begin() + blackIndex, 0);
> +	const float divisor = kGammaLookupSize - blackIndex - 1.0;
> +	for (unsigned int i = blackIndex; i < kGammaLookupSize; i++)

Same here.

> +		gammaTable[i] = UINT8_MAX * powf((i - blackIndex) / divisor,

std::powf

> +						 context.configuration.gamma);
> +	context.activeState.gamma.blackLevel = blackLevel;
> +}
> +
> +void Gamma::prepare(IPAContext &context,
> +		    [[maybe_unused]] const uint32_t frame,
> +		    [[maybe_unused]] IPAFrameContext &frameContext,
> +		    [[maybe_unused]] DebayerParams *params)
> +{
> +	/*
> +	 * Update the gamma table if needed. This means if black level changes and
> +	 * since the black level gets updated only if a lower value is observed,
> +	 * it's not permanently prone to minor fluctuations or rounding errors.

Please reflow to 80 columns.

> +	 */
> +	if (context.activeState.gamma.blackLevel != context.activeState.black.level)
> +		updateGammaTable(context);
> +}
> +
> +REGISTER_IPA_ALGORITHM(Gamma, "Gamma")
> +
> +} /* namespace ipa::soft::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/simple/algorithms/gamma.h b/src/ipa/simple/algorithms/gamma.h
> new file mode 100644
> index 00000000..43e88e87
> --- /dev/null
> +++ b/src/ipa/simple/algorithms/gamma.h
> @@ -0,0 +1,42 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Red Hat Inc.
> + *
> + * Gamma table construction
> + */
> +
> +#pragma once
> +
> +#include <libcamera/controls.h>
> +
> +#include "libcamera/internal/software_isp/debayer_params.h"
> +
> +#include "algorithm.h"
> +#include "ipa_context.h"
> +
> +namespace libcamera {
> +
> +namespace ipa::soft::algorithms {
> +
> +static constexpr unsigned int kGammaLookupSize = 1024;
> +
> +class Gamma : public Algorithm
> +{
> +public:
> +	Gamma() = default;
> +	~Gamma() = default;
> +
> +	int init(IPAContext &context, const YamlObject &tuningData)
> +		override;
> +	void prepare(IPAContext &context,
> +		     const uint32_t frame,
> +		     IPAFrameContext &frameContext,
> +		     DebayerParams *params) override;
> +
> +private:
> +	void updateGammaTable(IPAContext &context);
> +};
> +
> +} /* namespace ipa::soft::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
> new file mode 100644
> index 00000000..748f10aa
> --- /dev/null
> +++ b/src/ipa/simple/algorithms/lut.cpp
> @@ -0,0 +1,57 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Red Hat Inc.
> + *
> + * Lookup table construction
> + */
> +
> +#include "lut.h"
> +
> +#include <algorithm>
> +#include <stdint.h>
> +
> +#include <libcamera/base/log.h>
> +
> +#include "simple/ipa_context.h"
> +
> +#include "gamma.h"
> +
> +namespace libcamera {
> +
> +namespace ipa::soft::algorithms {
> +
> +int Lut::init(IPAContext &context,
> +	      [[maybe_unused]] const YamlObject &tuningData)
> +{
> +	auto &gains = context.activeState.gains;
> +	gains.red = gains.green = gains.blue = 1.0;

That looks wrong, the Awb algorithm does this already.

> +
> +	return 0;
> +}
> +
> +void Lut::prepare(IPAContext &context,
> +		  [[maybe_unused]] const uint32_t frame,
> +		  [[maybe_unused]] IPAFrameContext &frameContext,
> +		  DebayerParams *params)
> +{
> +	auto &gains = context.activeState.gains;
> +	auto &gammaTable = context.activeState.gamma.gammaTable;
> +	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
> +		constexpr unsigned int div =
> +			static_cast<double>(DebayerParams::kRGBLookupSize) * 256 / kGammaLookupSize;
> +		/* Apply gamma after gain! */
> +		unsigned int idx;
> +		idx = std::min({ i * gains.red / div, kGammaLookupSize - 1 });
> +		params->red[i] = gammaTable[idx];
> +		idx = std::min({ i * gains.green / div, kGammaLookupSize - 1 });
> +		params->green[i] = gammaTable[idx];
> +		idx = std::min({ i * gains.blue / div, kGammaLookupSize - 1 });
> +		params->blue[i] = gammaTable[idx];
> +	}

Why is this a separate algorithm, why isn't it part of Gamma ?

> +}
> +
> +REGISTER_IPA_ALGORITHM(Lut, "Lut")
> +
> +} /* namespace ipa::soft::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/simple/algorithms/lut.h b/src/ipa/simple/algorithms/lut.h
> new file mode 100644
> index 00000000..5b5e554e
> --- /dev/null
> +++ b/src/ipa/simple/algorithms/lut.h
> @@ -0,0 +1,37 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Red Hat Inc.
> + *
> + * Lookup table construction
> + */
> +
> +#pragma once
> +
> +#include <libcamera/controls.h>
> +
> +#include "libcamera/internal/software_isp/debayer_params.h"
> +
> +#include "algorithm.h"
> +#include "ipa_context.h"
> +
> +namespace libcamera {
> +
> +namespace ipa::soft::algorithms {
> +
> +class Lut : public Algorithm
> +{
> +public:
> +	Lut() = default;
> +	~Lut() = default;
> +
> +	int init(IPAContext &context, const YamlObject &tuningData)
> +		override;
> +	void prepare(IPAContext &context,
> +		     const uint32_t frame,
> +		     IPAFrameContext &frameContext,
> +		     DebayerParams *params) override;
> +};
> +
> +} /* namespace ipa::soft::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/simple/algorithms/meson.build b/src/ipa/simple/algorithms/meson.build
> index 1f63c220..68e5aa58 100644
> --- a/src/ipa/simple/algorithms/meson.build
> +++ b/src/ipa/simple/algorithms/meson.build
> @@ -1,5 +1,8 @@
>  # SPDX-License-Identifier: CC0-1.0
>  
>  soft_simple_ipa_algorithms = files([
> +    'awb.cpp',
>      'blc.cpp',
> +    'gamma.cpp',
> +    'lut.cpp',
>  ])
> diff --git a/src/ipa/simple/data/uncalibrated.yaml b/src/ipa/simple/data/uncalibrated.yaml
> index e0d03d96..deaea6b1 100644
> --- a/src/ipa/simple/data/uncalibrated.yaml
> +++ b/src/ipa/simple/data/uncalibrated.yaml
> @@ -4,4 +4,7 @@
>  version: 1
>  algorithms:
>    - BlackLevel:
> +  - Gamma:
> +  - Awb:
> +  - Lut:
>  ...
> diff --git a/src/ipa/simple/ipa_context.cpp b/src/ipa/simple/ipa_context.cpp
> index 268cff32..5fa492cb 100644
> --- a/src/ipa/simple/ipa_context.cpp
> +++ b/src/ipa/simple/ipa_context.cpp
> @@ -50,6 +50,11 @@ namespace libcamera::ipa::soft {
>   * \brief The current state of IPA algorithms
>   */
>  
> +/**
> + * \var IPASessionConfiguration::gamma
> + * \brief Gamma value to be used in the raw image processing
> + */
> +
>  /**
>   * \var IPAActiveState::black
>   * \brief Context for the Black Level algorithm
> @@ -58,4 +63,29 @@ namespace libcamera::ipa::soft {
>   * \brief Current determined black level
>   */
>  
> +/**
> + * \var IPAActiveState::gains
> + * \brief Context for gains in the Colors algorithm
> + *
> + * \var IPAActiveState::gains.red
> + * \brief Gain of red color
> + *
> + * \var IPAActiveState::gains.green
> + * \brief Gain of green color
> + *
> + * \var IPAActiveState::gains.blue
> + * \brief Gain of blue color
> + */
> +
> +/**
> + * \var IPAActiveState::gamma
> + * \brief Context for gamma in the Colors algorithm
> + *
> + * \var IPAActiveState::gamma.gammaTable
> + * \brief Computed gamma table
> + *
> + * \var IPAActiveState::gamma.blackLevel
> + * \brief Black level used for the gamma table computation
> + */
> +
>  } /* namespace libcamera::ipa::soft */
> diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
> index 22156569..f8b8834d 100644
> --- a/src/ipa/simple/ipa_context.h
> +++ b/src/ipa/simple/ipa_context.h
> @@ -7,6 +7,7 @@
>  
>  #pragma once
>  
> +#include <array>
>  #include <stdint.h>
>  
>  #include <libipa/fc_queue.h>
> @@ -16,12 +17,23 @@ namespace libcamera {
>  namespace ipa::soft {
>  
>  struct IPASessionConfiguration {
> +	float gamma;
>  };
>  
>  struct IPAActiveState {
>  	struct {
>  		uint8_t level;
>  	} black;

Blank line. Same below.

> +	struct {
> +		unsigned int red;
> +		unsigned int green;
> +		unsigned int blue;
> +	} gains;
> +	static constexpr unsigned int kGammaLookupSize = 1024;

This duplicates the kGammaLookupSize from
src/ipa/simple/algorithms/gamma.h. 

> +	struct {
> +		std::array<double, kGammaLookupSize> gammaTable;
> +		uint8_t blackLevel;
> +	} gamma;
>  };
>  
>  struct IPAFrameContext : public FrameContext {
> diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp
> index a1bd2f0c..8f01bf7d 100644
> --- a/src/ipa/simple/soft_simple.cpp
> +++ b/src/ipa/simple/soft_simple.cpp
> @@ -5,8 +5,6 @@
>   * Simple Software Image Processing Algorithm module
>   */
>  
> -#include <cmath>
> -#include <numeric>
>  #include <stdint.h>
>  #include <sys/mman.h>
>  
> @@ -93,9 +91,6 @@ private:
>  	std::unique_ptr<CameraSensorHelper> camHelper_;
>  	ControlInfoMap sensorInfoMap_;
>  
> -	static constexpr unsigned int kGammaLookupSize = 1024;
> -	std::array<uint8_t, kGammaLookupSize> gammaTable_;
> -	int lastBlackLevel_ = -1;
>  	/* Local parameter storage */
>  	struct IPAContext context_;
>  
> @@ -283,6 +278,7 @@ void IPASoftSimple::prepare(const uint32_t frame)
>  	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
>  	for (auto const &algo : algorithms())
>  		algo->prepare(context_, frame, frameContext, params_);
> +	setIspParams.emit();
>  }
>  
>  void IPASoftSimple::processStats(const uint32_t frame,
> @@ -300,62 +296,6 @@ void IPASoftSimple::processStats(const uint32_t frame,
>  	for (auto const &algo : algorithms())
>  		algo->process(context_, frame, frameContext, stats_, metadata);
>  
> -	SwIspStats::Histogram histogram = stats_->yHistogram;
> -	const uint8_t blackLevel = context_.activeState.black.level;
> -
> -	/*
> -	 * Black level must be subtracted to get the correct AWB ratios, they
> -	 * would be off if they were computed from the whole brightness range
> -	 * rather than from the sensor range.
> -	 */
> -	const uint64_t nPixels = std::accumulate(
> -		histogram.begin(), histogram.end(), 0);
> -	const uint64_t offset = blackLevel * nPixels;
> -	const uint64_t sumR = stats_->sumR_ - offset / 4;
> -	const uint64_t sumG = stats_->sumG_ - offset / 2;
> -	const uint64_t sumB = stats_->sumB_ - offset / 4;
> -
> -	/*
> -	 * Calculate red and blue gains for AWB.
> -	 * Clamp max gain at 4.0, this also avoids 0 division.
> -	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
> -	 */
> -	const unsigned int gainR = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
> -	const unsigned int gainB = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
> -	/* Green gain and gamma values are fixed */
> -	constexpr unsigned int gainG = 256;
> -
> -	/* Update the gamma table if needed */
> -	if (blackLevel != lastBlackLevel_) {
> -		constexpr float gamma = 0.5;
> -		const unsigned int blackIndex = blackLevel * kGammaLookupSize / 256;
> -		std::fill(gammaTable_.begin(), gammaTable_.begin() + blackIndex, 0);
> -		const float divisor = kGammaLookupSize - blackIndex - 1.0;
> -		for (unsigned int i = blackIndex; i < kGammaLookupSize; i++)
> -			gammaTable_[i] = UINT8_MAX *
> -					 std::pow((i - blackIndex) / divisor, gamma);
> -
> -		lastBlackLevel_ = blackLevel;
> -	}
> -
> -	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
> -		constexpr unsigned int div =
> -			DebayerParams::kRGBLookupSize * 256 / kGammaLookupSize;
> -		unsigned int idx;
> -
> -		/* Apply gamma after gain! */
> -		idx = std::min({ i * gainR / div, (kGammaLookupSize - 1) });
> -		params_->red[i] = gammaTable_[idx];
> -
> -		idx = std::min({ i * gainG / div, (kGammaLookupSize - 1) });
> -		params_->green[i] = gammaTable_[idx];
> -
> -		idx = std::min({ i * gainB / div, (kGammaLookupSize - 1) });
> -		params_->blue[i] = gammaTable_[idx];
> -	}
> -
> -	setIspParams.emit();
> -
>  	/* \todo Switch to the libipa/algorithm.h API someday. */
>  
>  	/*
> @@ -372,6 +312,7 @@ void IPASoftSimple::processStats(const uint32_t frame,
>  	 * Calculate Mean Sample Value (MSV) according to formula from:
>  	 * https://www.araa.asn.au/acra/acra2007/papers/paper84final.pdf
>  	 */
> +	const uint8_t blackLevel = context_.activeState.black.level;
>  	const unsigned int blackLevelHistIdx =
>  		blackLevel / (256 / SwIspStats::kYHistogramSize);
>  	const unsigned int histogramSize =
> @@ -421,7 +362,8 @@ void IPASoftSimple::processStats(const uint32_t frame,
>  
>  	LOG(IPASoft, Debug) << "exposureMSV " << exposureMSV
>  			    << " exp " << exposure_ << " again " << again_
> -			    << " gain R/B " << gainR << "/" << gainB
> +			    << " gain R/B " << context_.activeState.gains.red
> +			    << "/" << context_.activeState.gains.blue

That's already printed in Awb::process(), does it need to be duplicated
here ?

>  			    << " black level " << static_cast<unsigned int>(blackLevel);
>  }
>

Hi Laurent,

thank you for review.

Laurent Pinchart <laurent.pinchart@ideasonboard.com> writes:

> Hi Milan,
>
> Thank you for the patch.
>
> On Fri, Aug 30, 2024 at 09:25:50AM +0200, Milan Zamazal wrote:
>> After black level handling has been moved to an algorithm module, white
>> balance and the construction of color tables can be moved to algorithm
>> modules too.
>> 
>> This time, the moved code is split between stats processing and
>> parameter construction methods.  It is also split to three algorithm
>> modules:
>> 
>> - Gamma table computation.  This is actually independent of color
>>   handling.
>> 
>> - White balance computation.
>> 
>> - Color lookup tables construction.  While this applies the color gains
>>   computed by the white balance algorithm, it is not directly related to
>>   white balance.  We may want to modify the color lookup tables in
>>   future according to other parameters than just gamma and white balance
>>   gains.
>> 
>> This is the only part of the software ISP algorithms that sets the
>> parameters so emitting setIspParams can be moved to prepare() method.
>> 
>> A more natural representation of the gains (and black level) would be
>> floating point numbers.  This is not done here in order to minimize
>> changes in code movements.  It will be addressed in a followup patch.
>> 
>> Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
>> ---
>>  src/ipa/simple/algorithms/awb.cpp     | 70 +++++++++++++++++++++++++++
>>  src/ipa/simple/algorithms/awb.h       | 38 +++++++++++++++
>>  src/ipa/simple/algorithms/gamma.cpp   | 64 ++++++++++++++++++++++++
>>  src/ipa/simple/algorithms/gamma.h     | 42 ++++++++++++++++
>>  src/ipa/simple/algorithms/lut.cpp     | 57 ++++++++++++++++++++++
>>  src/ipa/simple/algorithms/lut.h       | 37 ++++++++++++++
>>  src/ipa/simple/algorithms/meson.build |  3 ++
>>  src/ipa/simple/data/uncalibrated.yaml |  3 ++
>>  src/ipa/simple/ipa_context.cpp        | 30 ++++++++++++
>>  src/ipa/simple/ipa_context.h          | 12 +++++
>>  src/ipa/simple/soft_simple.cpp        | 66 ++-----------------------
>>  11 files changed, 360 insertions(+), 62 deletions(-)
>>  create mode 100644 src/ipa/simple/algorithms/awb.cpp
>>  create mode 100644 src/ipa/simple/algorithms/awb.h
>>  create mode 100644 src/ipa/simple/algorithms/gamma.cpp
>>  create mode 100644 src/ipa/simple/algorithms/gamma.h
>>  create mode 100644 src/ipa/simple/algorithms/lut.cpp
>>  create mode 100644 src/ipa/simple/algorithms/lut.h
>> 
>> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
>> new file mode 100644
>> index 00000000..4b49996a
>> --- /dev/null
>> +++ b/src/ipa/simple/algorithms/awb.cpp
>> @@ -0,0 +1,70 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2024, Red Hat Inc.
>> + *
>> + * Auto white balance
>> + */
>> +
>> +#include "awb.h"
>> +
>> +#include <numeric>
>> +#include <stdint.h>
>> +
>> +#include <libcamera/base/log.h>
>> +
>> +#include "simple/ipa_context.h"
>> +
>> +namespace libcamera {
>> +
>> +LOG_DEFINE_CATEGORY(IPASoftAwb)
>> +
>> +namespace ipa::soft::algorithms {
>> +
>> +int Awb::init(IPAContext &context,
>> +	      [[maybe_unused]] const YamlObject &tuningData)
>> +{
>> +	auto &gains = context.activeState.gains;
>> +	gains.red = gains.green = gains.blue = 256;
>> +
>> +	return 0;
>> +}
>> +
>> +void Awb::process(IPAContext &context,
>> +		  [[maybe_unused]] const uint32_t frame,
>> +		  [[maybe_unused]] IPAFrameContext &frameContext,
>> +		  const SwIspStats *stats,
>> +		  [[maybe_unused]] ControlList &metadata)
>> +{
>> +	const SwIspStats::Histogram &histogram = stats->yHistogram;
>> +	const uint8_t blackLevel = context.activeState.black.level;
>> +
>> +	/*
>> +	 * Black level must be subtracted to get the correct AWB ratios, they
>> +	 * would be off if they were computed from the whole brightness range
>> +	 * rather than from the sensor range.
>> +	 */
>> +	const uint64_t nPixels = std::accumulate(
>> +		histogram.begin(), histogram.end(), 0);
>> +	const uint64_t offset = blackLevel * nPixels;
>> +	const uint64_t sumR = stats->sumR_ - offset / 4;
>> +	const uint64_t sumG = stats->sumG_ - offset / 2;
>> +	const uint64_t sumB = stats->sumB_ - offset / 4;
>> +
>> +	/*
>> +	 * Calculate red and blue gains for AWB.
>> +	 * Clamp max gain at 4.0, this also avoids 0 division.
>> +	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
>> +	 */
>> +	auto &gains = context.activeState.gains;
>> +	gains.red = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
>> +	gains.blue = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
>> +	/* Green gain is fixed to 256 */
>> +
>> +	LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
>> +}
>> +
>> +REGISTER_IPA_ALGORITHM(Awb, "Awb")
>> +
>> +} /* namespace ipa::soft::algorithms */
>> +
>> +} /* namespace libcamera */
>> diff --git a/src/ipa/simple/algorithms/awb.h b/src/ipa/simple/algorithms/awb.h
>> new file mode 100644
>> index 00000000..c0b88bec
>> --- /dev/null
>> +++ b/src/ipa/simple/algorithms/awb.h
>> @@ -0,0 +1,38 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2024, Red Hat Inc.
>> + *
>> + * Auto white balance
>> + */
>> +
>> +#pragma once
>> +
>> +#include <libcamera/controls.h>
>> +
>> +#include "libcamera/internal/software_isp/swisp_stats.h"
>> +
>> +#include "algorithm.h"
>> +#include "ipa_context.h"
>
> As with the previous patch, I think you can drop all the includes except
> algorithm.h. Same for the other algorithms.
>
>> +
>> +namespace libcamera {
>> +
>> +namespace ipa::soft::algorithms {
>> +
>> +class Awb : public Algorithm
>> +{
>> +public:
>> +	Awb() = default;
>> +	~Awb() = default;
>> +
>> +	int init(IPAContext &context, const YamlObject &tuningData)
>> +		override;
>
> No need to split this on two lines. Same below.
>
>> +	void process(IPAContext &context,
>> +		     const uint32_t frame,
>> +		     IPAFrameContext &frameContext,
>> +		     const SwIspStats *stats,
>> +		     ControlList &metadata) override;
>> +};
>> +
>> +} /* namespace ipa::soft::algorithms */
>> +
>> +} /* namespace libcamera */
>> diff --git a/src/ipa/simple/algorithms/gamma.cpp b/src/ipa/simple/algorithms/gamma.cpp
>> new file mode 100644
>> index 00000000..0b8ec5ee
>> --- /dev/null
>> +++ b/src/ipa/simple/algorithms/gamma.cpp
>> @@ -0,0 +1,64 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2024, Red Hat Inc.
>> + *
>> + * Gamma table construction
>> + */
>> +
>> +#include "gamma.h"
>> +
>> +#include <algorithm>
>> +#include <cmath>
>> +#include <stdint.h>
>> +
>> +#include <libcamera/base/log.h>
>> +
>> +#include "simple/ipa_context.h"
>> +
>> +namespace libcamera {
>> +
>> +namespace ipa::soft::algorithms {
>> +
>> +int Gamma::init(IPAContext &context,
>> +		[[maybe_unused]] const YamlObject &tuningData)
>> +{
>> +	/* Gamma value is fixed */
>> +	context.configuration.gamma = 0.5;
>> +	updateGammaTable(context);
>
> Same question as before, does this belong to .init() ? Actually, given
> that prepare() will always be called to calculate ISP parameters, do you
> even need to initialize the gamme table ?

The update of the gamma table in prepare() is conditional and I wouldn't
rely on the initial values of the variables used in the condition;
making sure the table is initialized is safer and it doesn't harm to do
it in init().  Once the gamma table is initialized, we can rely on the
conditional update in prepare(), so there is no need to update the gamma
table in configure() again.

>> +
>> +	return 0;
>> +}
>> +
>> +void Gamma::updateGammaTable(IPAContext &context)
>> +{
>> +	auto &gammaTable = context.activeState.gamma.gammaTable;
>> +	auto blackLevel = context.activeState.black.level;
>> +	const unsigned int blackIndex =
>> +		blackLevel * IPAActiveState::kGammaLookupSize / 256;
>
> Use gammaTable.size() instead of kGammaLookupSize.
>
>> +	std::fill(gammaTable.begin(), gammaTable.begin() + blackIndex, 0);
>> +	const float divisor = kGammaLookupSize - blackIndex - 1.0;
>> +	for (unsigned int i = blackIndex; i < kGammaLookupSize; i++)
>
> Same here.
>
>> +		gammaTable[i] = UINT8_MAX * powf((i - blackIndex) / divisor,
>
> std::powf

std::pow actually, I suppose.

>> +						 context.configuration.gamma);
>> +	context.activeState.gamma.blackLevel = blackLevel;
>> +}
>> +
>> +void Gamma::prepare(IPAContext &context,
>> +		    [[maybe_unused]] const uint32_t frame,
>> +		    [[maybe_unused]] IPAFrameContext &frameContext,
>> +		    [[maybe_unused]] DebayerParams *params)
>> +{
>> +	/*
>> +	 * Update the gamma table if needed. This means if black level changes and
>> +	 * since the black level gets updated only if a lower value is observed,
>> +	 * it's not permanently prone to minor fluctuations or rounding errors.
>
> Please reflow to 80 columns.
>
>> +	 */
>> +	if (context.activeState.gamma.blackLevel != context.activeState.black.level)
>> +		updateGammaTable(context);
>> +}
>> +
>> +REGISTER_IPA_ALGORITHM(Gamma, "Gamma")
>> +
>> +} /* namespace ipa::soft::algorithms */
>> +
>> +} /* namespace libcamera */
>> diff --git a/src/ipa/simple/algorithms/gamma.h b/src/ipa/simple/algorithms/gamma.h
>> new file mode 100644
>> index 00000000..43e88e87
>> --- /dev/null
>> +++ b/src/ipa/simple/algorithms/gamma.h
>> @@ -0,0 +1,42 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2024, Red Hat Inc.
>> + *
>> + * Gamma table construction
>> + */
>> +
>> +#pragma once
>> +
>> +#include <libcamera/controls.h>
>> +
>> +#include "libcamera/internal/software_isp/debayer_params.h"
>> +
>> +#include "algorithm.h"
>> +#include "ipa_context.h"
>> +
>> +namespace libcamera {
>> +
>> +namespace ipa::soft::algorithms {
>> +
>> +static constexpr unsigned int kGammaLookupSize = 1024;
>> +
>> +class Gamma : public Algorithm
>> +{
>> +public:
>> +	Gamma() = default;
>> +	~Gamma() = default;
>> +
>> +	int init(IPAContext &context, const YamlObject &tuningData)
>> +		override;
>> +	void prepare(IPAContext &context,
>> +		     const uint32_t frame,
>> +		     IPAFrameContext &frameContext,
>> +		     DebayerParams *params) override;
>> +
>> +private:
>> +	void updateGammaTable(IPAContext &context);
>> +};
>> +
>> +} /* namespace ipa::soft::algorithms */
>> +
>> +} /* namespace libcamera */
>> diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
>> new file mode 100644
>> index 00000000..748f10aa
>> --- /dev/null
>> +++ b/src/ipa/simple/algorithms/lut.cpp
>> @@ -0,0 +1,57 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2024, Red Hat Inc.
>> + *
>> + * Lookup table construction
>> + */
>> +
>> +#include "lut.h"
>> +
>> +#include <algorithm>
>> +#include <stdint.h>
>> +
>> +#include <libcamera/base/log.h>
>> +
>> +#include "simple/ipa_context.h"
>> +
>> +#include "gamma.h"
>> +
>> +namespace libcamera {
>> +
>> +namespace ipa::soft::algorithms {
>> +
>> +int Lut::init(IPAContext &context,
>> +	      [[maybe_unused]] const YamlObject &tuningData)
>> +{
>> +	auto &gains = context.activeState.gains;
>> +	gains.red = gains.green = gains.blue = 1.0;
>
> That looks wrong, the Awb algorithm does this already.

Indeed, it doesn't belong here.

>> +
>> +	return 0;
>> +}
>> +
>> +void Lut::prepare(IPAContext &context,
>> +		  [[maybe_unused]] const uint32_t frame,
>> +		  [[maybe_unused]] IPAFrameContext &frameContext,
>> +		  DebayerParams *params)
>> +{
>> +	auto &gains = context.activeState.gains;
>> +	auto &gammaTable = context.activeState.gamma.gammaTable;
>> +	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
>> +		constexpr unsigned int div =
>> +			static_cast<double>(DebayerParams::kRGBLookupSize) * 256 / kGammaLookupSize;
>> +		/* Apply gamma after gain! */
>> +		unsigned int idx;
>> +		idx = std::min({ i * gains.red / div, kGammaLookupSize - 1 });
>> +		params->red[i] = gammaTable[idx];
>> +		idx = std::min({ i * gains.green / div, kGammaLookupSize - 1 });
>> +		params->green[i] = gammaTable[idx];
>> +		idx = std::min({ i * gains.blue / div, kGammaLookupSize - 1 });
>> +		params->blue[i] = gammaTable[idx];
>> +	}
>
> Why is this a separate algorithm, why isn't it part of Gamma ?

Well, constructing the gamma table and the color lookup tables are two
different things.  While the gammaTable looks like a utility just for
the color lookup tables here, it may not always be the case, for
instance contrast adjustment may be implemented by modifying the gamma
table. 

But I don't have a strong opinion on this and I can merge the two.

>> +}
>> +
>> +REGISTER_IPA_ALGORITHM(Lut, "Lut")
>> +
>> +} /* namespace ipa::soft::algorithms */
>> +
>> +} /* namespace libcamera */
>> diff --git a/src/ipa/simple/algorithms/lut.h b/src/ipa/simple/algorithms/lut.h
>> new file mode 100644
>> index 00000000..5b5e554e
>> --- /dev/null
>> +++ b/src/ipa/simple/algorithms/lut.h
>> @@ -0,0 +1,37 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2024, Red Hat Inc.
>> + *
>> + * Lookup table construction
>> + */
>> +
>> +#pragma once
>> +
>> +#include <libcamera/controls.h>
>> +
>> +#include "libcamera/internal/software_isp/debayer_params.h"
>> +
>> +#include "algorithm.h"
>> +#include "ipa_context.h"
>> +
>> +namespace libcamera {
>> +
>> +namespace ipa::soft::algorithms {
>> +
>> +class Lut : public Algorithm
>> +{
>> +public:
>> +	Lut() = default;
>> +	~Lut() = default;
>> +
>> +	int init(IPAContext &context, const YamlObject &tuningData)
>> +		override;
>> +	void prepare(IPAContext &context,
>> +		     const uint32_t frame,
>> +		     IPAFrameContext &frameContext,
>> +		     DebayerParams *params) override;
>> +};
>> +
>> +} /* namespace ipa::soft::algorithms */
>> +
>> +} /* namespace libcamera */
>> diff --git a/src/ipa/simple/algorithms/meson.build b/src/ipa/simple/algorithms/meson.build
>> index 1f63c220..68e5aa58 100644
>> --- a/src/ipa/simple/algorithms/meson.build
>> +++ b/src/ipa/simple/algorithms/meson.build
>> @@ -1,5 +1,8 @@
>>  # SPDX-License-Identifier: CC0-1.0
>>  
>>  soft_simple_ipa_algorithms = files([
>> +    'awb.cpp',
>>      'blc.cpp',
>> +    'gamma.cpp',
>> +    'lut.cpp',
>>  ])
>> diff --git a/src/ipa/simple/data/uncalibrated.yaml b/src/ipa/simple/data/uncalibrated.yaml
>> index e0d03d96..deaea6b1 100644
>> --- a/src/ipa/simple/data/uncalibrated.yaml
>> +++ b/src/ipa/simple/data/uncalibrated.yaml
>> @@ -4,4 +4,7 @@
>>  version: 1
>>  algorithms:
>>    - BlackLevel:
>> +  - Gamma:
>> +  - Awb:
>> +  - Lut:
>>  ...
>> diff --git a/src/ipa/simple/ipa_context.cpp b/src/ipa/simple/ipa_context.cpp
>> index 268cff32..5fa492cb 100644
>> --- a/src/ipa/simple/ipa_context.cpp
>> +++ b/src/ipa/simple/ipa_context.cpp
>> @@ -50,6 +50,11 @@ namespace libcamera::ipa::soft {
>>   * \brief The current state of IPA algorithms
>>   */
>>  
>> +/**
>> + * \var IPASessionConfiguration::gamma
>> + * \brief Gamma value to be used in the raw image processing
>> + */
>> +
>>  /**
>>   * \var IPAActiveState::black
>>   * \brief Context for the Black Level algorithm
>> @@ -58,4 +63,29 @@ namespace libcamera::ipa::soft {
>>   * \brief Current determined black level
>>   */
>>  
>> +/**
>> + * \var IPAActiveState::gains
>> + * \brief Context for gains in the Colors algorithm
>> + *
>> + * \var IPAActiveState::gains.red
>> + * \brief Gain of red color
>> + *
>> + * \var IPAActiveState::gains.green
>> + * \brief Gain of green color
>> + *
>> + * \var IPAActiveState::gains.blue
>> + * \brief Gain of blue color
>> + */
>> +
>> +/**
>> + * \var IPAActiveState::gamma
>> + * \brief Context for gamma in the Colors algorithm
>> + *
>> + * \var IPAActiveState::gamma.gammaTable
>> + * \brief Computed gamma table
>> + *
>> + * \var IPAActiveState::gamma.blackLevel
>> + * \brief Black level used for the gamma table computation
>> + */
>> +
>>  } /* namespace libcamera::ipa::soft */
>> diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
>> index 22156569..f8b8834d 100644
>> --- a/src/ipa/simple/ipa_context.h
>> +++ b/src/ipa/simple/ipa_context.h
>> @@ -7,6 +7,7 @@
>>  
>>  #pragma once
>>  
>> +#include <array>
>>  #include <stdint.h>
>>  
>>  #include <libipa/fc_queue.h>
>> @@ -16,12 +17,23 @@ namespace libcamera {
>>  namespace ipa::soft {
>>  
>>  struct IPASessionConfiguration {
>> +	float gamma;
>>  };
>>  
>>  struct IPAActiveState {
>>  	struct {
>>  		uint8_t level;
>>  	} black;
>
> Blank line. Same below.
>
>> +	struct {
>> +		unsigned int red;
>> +		unsigned int green;
>> +		unsigned int blue;
>> +	} gains;
>> +	static constexpr unsigned int kGammaLookupSize = 1024;
>
> This duplicates the kGammaLookupSize from
> src/ipa/simple/algorithms/gamma.h. 

Yes.  The constant in gamma.h is actually not needed when replacing it
with size() calls, I'll remove it.

>> +	struct {
>> +		std::array<double, kGammaLookupSize> gammaTable;
>> +		uint8_t blackLevel;
>> +	} gamma;
>>  };
>>  
>>  struct IPAFrameContext : public FrameContext {
>> diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp
>> index a1bd2f0c..8f01bf7d 100644
>> --- a/src/ipa/simple/soft_simple.cpp
>> +++ b/src/ipa/simple/soft_simple.cpp
>> @@ -5,8 +5,6 @@
>>   * Simple Software Image Processing Algorithm module
>>   */
>>  
>> -#include <cmath>
>> -#include <numeric>
>>  #include <stdint.h>
>>  #include <sys/mman.h>
>>  
>> @@ -93,9 +91,6 @@ private:
>>  	std::unique_ptr<CameraSensorHelper> camHelper_;
>>  	ControlInfoMap sensorInfoMap_;
>>  
>> -	static constexpr unsigned int kGammaLookupSize = 1024;
>> -	std::array<uint8_t, kGammaLookupSize> gammaTable_;
>> -	int lastBlackLevel_ = -1;
>>  	/* Local parameter storage */
>>  	struct IPAContext context_;
>>  
>> @@ -283,6 +278,7 @@ void IPASoftSimple::prepare(const uint32_t frame)
>>  	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
>>  	for (auto const &algo : algorithms())
>>  		algo->prepare(context_, frame, frameContext, params_);
>> +	setIspParams.emit();
>>  }
>>  
>>  void IPASoftSimple::processStats(const uint32_t frame,
>> @@ -300,62 +296,6 @@ void IPASoftSimple::processStats(const uint32_t frame,
>>  	for (auto const &algo : algorithms())
>>  		algo->process(context_, frame, frameContext, stats_, metadata);
>>  
>> -	SwIspStats::Histogram histogram = stats_->yHistogram;
>> -	const uint8_t blackLevel = context_.activeState.black.level;
>> -
>> -	/*
>> -	 * Black level must be subtracted to get the correct AWB ratios, they
>> -	 * would be off if they were computed from the whole brightness range
>> -	 * rather than from the sensor range.
>> -	 */
>> -	const uint64_t nPixels = std::accumulate(
>> -		histogram.begin(), histogram.end(), 0);
>> -	const uint64_t offset = blackLevel * nPixels;
>> -	const uint64_t sumR = stats_->sumR_ - offset / 4;
>> -	const uint64_t sumG = stats_->sumG_ - offset / 2;
>> -	const uint64_t sumB = stats_->sumB_ - offset / 4;
>> -
>> -	/*
>> -	 * Calculate red and blue gains for AWB.
>> -	 * Clamp max gain at 4.0, this also avoids 0 division.
>> -	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
>> -	 */
>> -	const unsigned int gainR = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
>> -	const unsigned int gainB = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
>> -	/* Green gain and gamma values are fixed */
>> -	constexpr unsigned int gainG = 256;
>> -
>> -	/* Update the gamma table if needed */
>> -	if (blackLevel != lastBlackLevel_) {
>> -		constexpr float gamma = 0.5;
>> -		const unsigned int blackIndex = blackLevel * kGammaLookupSize / 256;
>> -		std::fill(gammaTable_.begin(), gammaTable_.begin() + blackIndex, 0);
>> -		const float divisor = kGammaLookupSize - blackIndex - 1.0;
>> -		for (unsigned int i = blackIndex; i < kGammaLookupSize; i++)
>> -			gammaTable_[i] = UINT8_MAX *
>> -					 std::pow((i - blackIndex) / divisor, gamma);
>> -
>> -		lastBlackLevel_ = blackLevel;
>> -	}
>> -
>> -	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
>> -		constexpr unsigned int div =
>> -			DebayerParams::kRGBLookupSize * 256 / kGammaLookupSize;
>> -		unsigned int idx;
>> -
>> -		/* Apply gamma after gain! */
>> -		idx = std::min({ i * gainR / div, (kGammaLookupSize - 1) });
>> -		params_->red[i] = gammaTable_[idx];
>> -
>> -		idx = std::min({ i * gainG / div, (kGammaLookupSize - 1) });
>> -		params_->green[i] = gammaTable_[idx];
>> -
>> -		idx = std::min({ i * gainB / div, (kGammaLookupSize - 1) });
>> -		params_->blue[i] = gammaTable_[idx];
>> -	}
>> -
>> -	setIspParams.emit();
>> -
>>  	/* \todo Switch to the libipa/algorithm.h API someday. */
>>  
>>  	/*
>> @@ -372,6 +312,7 @@ void IPASoftSimple::processStats(const uint32_t frame,
>>  	 * Calculate Mean Sample Value (MSV) according to formula from:
>>  	 * https://www.araa.asn.au/acra/acra2007/papers/paper84final.pdf
>>  	 */
>> +	const uint8_t blackLevel = context_.activeState.black.level;
>>  	const unsigned int blackLevelHistIdx =
>>  		blackLevel / (256 / SwIspStats::kYHistogramSize);
>>  	const unsigned int histogramSize =
>> @@ -421,7 +362,8 @@ void IPASoftSimple::processStats(const uint32_t frame,
>>  
>>  	LOG(IPASoft, Debug) << "exposureMSV " << exposureMSV
>>  			    << " exp " << exposure_ << " again " << again_
>> -			    << " gain R/B " << gainR << "/" << gainB
>> +			    << " gain R/B " << context_.activeState.gains.red
>> +			    << "/" << context_.activeState.gains.blue
>
> That's already printed in Awb::process(), does it need to be duplicated
> here ?

I don't think so, I'll remove it here.

>>  			    << " black level " << static_cast<unsigned int>(blackLevel);
>>  }
>>

On Fri, Sep 06, 2024 at 12:41:07PM +0200, Milan Zamazal wrote:
> Laurent Pinchart writes:
> > On Fri, Aug 30, 2024 at 09:25:50AM +0200, Milan Zamazal wrote:
> >> After black level handling has been moved to an algorithm module, white
> >> balance and the construction of color tables can be moved to algorithm
> >> modules too.
> >> 
> >> This time, the moved code is split between stats processing and
> >> parameter construction methods.  It is also split to three algorithm
> >> modules:
> >> 
> >> - Gamma table computation.  This is actually independent of color
> >>   handling.
> >> 
> >> - White balance computation.
> >> 
> >> - Color lookup tables construction.  While this applies the color gains
> >>   computed by the white balance algorithm, it is not directly related to
> >>   white balance.  We may want to modify the color lookup tables in
> >>   future according to other parameters than just gamma and white balance
> >>   gains.
> >> 
> >> This is the only part of the software ISP algorithms that sets the
> >> parameters so emitting setIspParams can be moved to prepare() method.
> >> 
> >> A more natural representation of the gains (and black level) would be
> >> floating point numbers.  This is not done here in order to minimize
> >> changes in code movements.  It will be addressed in a followup patch.
> >> 
> >> Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
> >> ---
> >>  src/ipa/simple/algorithms/awb.cpp     | 70 +++++++++++++++++++++++++++
> >>  src/ipa/simple/algorithms/awb.h       | 38 +++++++++++++++
> >>  src/ipa/simple/algorithms/gamma.cpp   | 64 ++++++++++++++++++++++++
> >>  src/ipa/simple/algorithms/gamma.h     | 42 ++++++++++++++++
> >>  src/ipa/simple/algorithms/lut.cpp     | 57 ++++++++++++++++++++++
> >>  src/ipa/simple/algorithms/lut.h       | 37 ++++++++++++++
> >>  src/ipa/simple/algorithms/meson.build |  3 ++
> >>  src/ipa/simple/data/uncalibrated.yaml |  3 ++
> >>  src/ipa/simple/ipa_context.cpp        | 30 ++++++++++++
> >>  src/ipa/simple/ipa_context.h          | 12 +++++
> >>  src/ipa/simple/soft_simple.cpp        | 66 ++-----------------------
> >>  11 files changed, 360 insertions(+), 62 deletions(-)
> >>  create mode 100644 src/ipa/simple/algorithms/awb.cpp
> >>  create mode 100644 src/ipa/simple/algorithms/awb.h
> >>  create mode 100644 src/ipa/simple/algorithms/gamma.cpp
> >>  create mode 100644 src/ipa/simple/algorithms/gamma.h
> >>  create mode 100644 src/ipa/simple/algorithms/lut.cpp
> >>  create mode 100644 src/ipa/simple/algorithms/lut.h
> >> 
> >> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
> >> new file mode 100644
> >> index 00000000..4b49996a
> >> --- /dev/null
> >> +++ b/src/ipa/simple/algorithms/awb.cpp
> >> @@ -0,0 +1,70 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2024, Red Hat Inc.
> >> + *
> >> + * Auto white balance
> >> + */
> >> +
> >> +#include "awb.h"
> >> +
> >> +#include <numeric>
> >> +#include <stdint.h>
> >> +
> >> +#include <libcamera/base/log.h>
> >> +
> >> +#include "simple/ipa_context.h"
> >> +
> >> +namespace libcamera {
> >> +
> >> +LOG_DEFINE_CATEGORY(IPASoftAwb)
> >> +
> >> +namespace ipa::soft::algorithms {
> >> +
> >> +int Awb::init(IPAContext &context,
> >> +	      [[maybe_unused]] const YamlObject &tuningData)
> >> +{
> >> +	auto &gains = context.activeState.gains;
> >> +	gains.red = gains.green = gains.blue = 256;
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +void Awb::process(IPAContext &context,
> >> +		  [[maybe_unused]] const uint32_t frame,
> >> +		  [[maybe_unused]] IPAFrameContext &frameContext,
> >> +		  const SwIspStats *stats,
> >> +		  [[maybe_unused]] ControlList &metadata)
> >> +{
> >> +	const SwIspStats::Histogram &histogram = stats->yHistogram;
> >> +	const uint8_t blackLevel = context.activeState.black.level;
> >> +
> >> +	/*
> >> +	 * Black level must be subtracted to get the correct AWB ratios, they
> >> +	 * would be off if they were computed from the whole brightness range
> >> +	 * rather than from the sensor range.
> >> +	 */
> >> +	const uint64_t nPixels = std::accumulate(
> >> +		histogram.begin(), histogram.end(), 0);
> >> +	const uint64_t offset = blackLevel * nPixels;
> >> +	const uint64_t sumR = stats->sumR_ - offset / 4;
> >> +	const uint64_t sumG = stats->sumG_ - offset / 2;
> >> +	const uint64_t sumB = stats->sumB_ - offset / 4;
> >> +
> >> +	/*
> >> +	 * Calculate red and blue gains for AWB.
> >> +	 * Clamp max gain at 4.0, this also avoids 0 division.
> >> +	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
> >> +	 */
> >> +	auto &gains = context.activeState.gains;
> >> +	gains.red = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
> >> +	gains.blue = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
> >> +	/* Green gain is fixed to 256 */
> >> +
> >> +	LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
> >> +}
> >> +
> >> +REGISTER_IPA_ALGORITHM(Awb, "Awb")
> >> +
> >> +} /* namespace ipa::soft::algorithms */
> >> +
> >> +} /* namespace libcamera */
> >> diff --git a/src/ipa/simple/algorithms/awb.h b/src/ipa/simple/algorithms/awb.h
> >> new file mode 100644
> >> index 00000000..c0b88bec
> >> --- /dev/null
> >> +++ b/src/ipa/simple/algorithms/awb.h
> >> @@ -0,0 +1,38 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2024, Red Hat Inc.
> >> + *
> >> + * Auto white balance
> >> + */
> >> +
> >> +#pragma once
> >> +
> >> +#include <libcamera/controls.h>
> >> +
> >> +#include "libcamera/internal/software_isp/swisp_stats.h"
> >> +
> >> +#include "algorithm.h"
> >> +#include "ipa_context.h"
> >
> > As with the previous patch, I think you can drop all the includes except
> > algorithm.h. Same for the other algorithms.
> >
> >> +
> >> +namespace libcamera {
> >> +
> >> +namespace ipa::soft::algorithms {
> >> +
> >> +class Awb : public Algorithm
> >> +{
> >> +public:
> >> +	Awb() = default;
> >> +	~Awb() = default;
> >> +
> >> +	int init(IPAContext &context, const YamlObject &tuningData)
> >> +		override;
> >
> > No need to split this on two lines. Same below.
> >
> >> +	void process(IPAContext &context,
> >> +		     const uint32_t frame,
> >> +		     IPAFrameContext &frameContext,
> >> +		     const SwIspStats *stats,
> >> +		     ControlList &metadata) override;
> >> +};
> >> +
> >> +} /* namespace ipa::soft::algorithms */
> >> +
> >> +} /* namespace libcamera */
> >> diff --git a/src/ipa/simple/algorithms/gamma.cpp b/src/ipa/simple/algorithms/gamma.cpp
> >> new file mode 100644
> >> index 00000000..0b8ec5ee
> >> --- /dev/null
> >> +++ b/src/ipa/simple/algorithms/gamma.cpp
> >> @@ -0,0 +1,64 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2024, Red Hat Inc.
> >> + *
> >> + * Gamma table construction
> >> + */
> >> +
> >> +#include "gamma.h"
> >> +
> >> +#include <algorithm>
> >> +#include <cmath>
> >> +#include <stdint.h>
> >> +
> >> +#include <libcamera/base/log.h>
> >> +
> >> +#include "simple/ipa_context.h"
> >> +
> >> +namespace libcamera {
> >> +
> >> +namespace ipa::soft::algorithms {
> >> +
> >> +int Gamma::init(IPAContext &context,
> >> +		[[maybe_unused]] const YamlObject &tuningData)
> >> +{
> >> +	/* Gamma value is fixed */
> >> +	context.configuration.gamma = 0.5;
> >> +	updateGammaTable(context);
> >
> > Same question as before, does this belong to .init() ? Actually, given
> > that prepare() will always be called to calculate ISP parameters, do you
> > even need to initialize the gamme table ?
> 
> The update of the gamma table in prepare() is conditional and I wouldn't
> rely on the initial values of the variables used in the condition;
> making sure the table is initialized is safer and it doesn't harm to do
> it in init().  Once the gamma table is initialized, we can rely on the
> conditional update in prepare(), so there is no need to update the gamma
> table in configure() again.

Then I think it should be initialized in configure() instead, to avoid
retaining state between capture sessions.

> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +void Gamma::updateGammaTable(IPAContext &context)
> >> +{
> >> +	auto &gammaTable = context.activeState.gamma.gammaTable;
> >> +	auto blackLevel = context.activeState.black.level;
> >> +	const unsigned int blackIndex =
> >> +		blackLevel * IPAActiveState::kGammaLookupSize / 256;
> >
> > Use gammaTable.size() instead of kGammaLookupSize.
> >
> >> +	std::fill(gammaTable.begin(), gammaTable.begin() + blackIndex, 0);
> >> +	const float divisor = kGammaLookupSize - blackIndex - 1.0;
> >> +	for (unsigned int i = blackIndex; i < kGammaLookupSize; i++)
> >
> > Same here.
> >
> >> +		gammaTable[i] = UINT8_MAX * powf((i - blackIndex) / divisor,
> >
> > std::powf
> 
> std::pow actually, I suppose.

Yes.

> >> +						 context.configuration.gamma);
> >> +	context.activeState.gamma.blackLevel = blackLevel;
> >> +}
> >> +
> >> +void Gamma::prepare(IPAContext &context,
> >> +		    [[maybe_unused]] const uint32_t frame,
> >> +		    [[maybe_unused]] IPAFrameContext &frameContext,
> >> +		    [[maybe_unused]] DebayerParams *params)
> >> +{
> >> +	/*
> >> +	 * Update the gamma table if needed. This means if black level changes and
> >> +	 * since the black level gets updated only if a lower value is observed,
> >> +	 * it's not permanently prone to minor fluctuations or rounding errors.
> >
> > Please reflow to 80 columns.
> >
> >> +	 */
> >> +	if (context.activeState.gamma.blackLevel != context.activeState.black.level)
> >> +		updateGammaTable(context);
> >> +}
> >> +
> >> +REGISTER_IPA_ALGORITHM(Gamma, "Gamma")
> >> +
> >> +} /* namespace ipa::soft::algorithms */
> >> +
> >> +} /* namespace libcamera */
> >> diff --git a/src/ipa/simple/algorithms/gamma.h b/src/ipa/simple/algorithms/gamma.h
> >> new file mode 100644
> >> index 00000000..43e88e87
> >> --- /dev/null
> >> +++ b/src/ipa/simple/algorithms/gamma.h
> >> @@ -0,0 +1,42 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2024, Red Hat Inc.
> >> + *
> >> + * Gamma table construction
> >> + */
> >> +
> >> +#pragma once
> >> +
> >> +#include <libcamera/controls.h>
> >> +
> >> +#include "libcamera/internal/software_isp/debayer_params.h"
> >> +
> >> +#include "algorithm.h"
> >> +#include "ipa_context.h"
> >> +
> >> +namespace libcamera {
> >> +
> >> +namespace ipa::soft::algorithms {
> >> +
> >> +static constexpr unsigned int kGammaLookupSize = 1024;
> >> +
> >> +class Gamma : public Algorithm
> >> +{
> >> +public:
> >> +	Gamma() = default;
> >> +	~Gamma() = default;
> >> +
> >> +	int init(IPAContext &context, const YamlObject &tuningData)
> >> +		override;
> >> +	void prepare(IPAContext &context,
> >> +		     const uint32_t frame,
> >> +		     IPAFrameContext &frameContext,
> >> +		     DebayerParams *params) override;
> >> +
> >> +private:
> >> +	void updateGammaTable(IPAContext &context);
> >> +};
> >> +
> >> +} /* namespace ipa::soft::algorithms */
> >> +
> >> +} /* namespace libcamera */
> >> diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
> >> new file mode 100644
> >> index 00000000..748f10aa
> >> --- /dev/null
> >> +++ b/src/ipa/simple/algorithms/lut.cpp
> >> @@ -0,0 +1,57 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2024, Red Hat Inc.
> >> + *
> >> + * Lookup table construction
> >> + */
> >> +
> >> +#include "lut.h"
> >> +
> >> +#include <algorithm>
> >> +#include <stdint.h>
> >> +
> >> +#include <libcamera/base/log.h>
> >> +
> >> +#include "simple/ipa_context.h"
> >> +
> >> +#include "gamma.h"
> >> +
> >> +namespace libcamera {
> >> +
> >> +namespace ipa::soft::algorithms {
> >> +
> >> +int Lut::init(IPAContext &context,
> >> +	      [[maybe_unused]] const YamlObject &tuningData)
> >> +{
> >> +	auto &gains = context.activeState.gains;
> >> +	gains.red = gains.green = gains.blue = 1.0;
> >
> > That looks wrong, the Awb algorithm does this already.
> 
> Indeed, it doesn't belong here.
> 
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +void Lut::prepare(IPAContext &context,
> >> +		  [[maybe_unused]] const uint32_t frame,
> >> +		  [[maybe_unused]] IPAFrameContext &frameContext,
> >> +		  DebayerParams *params)
> >> +{
> >> +	auto &gains = context.activeState.gains;
> >> +	auto &gammaTable = context.activeState.gamma.gammaTable;
> >> +	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
> >> +		constexpr unsigned int div =
> >> +			static_cast<double>(DebayerParams::kRGBLookupSize) * 256 / kGammaLookupSize;
> >> +		/* Apply gamma after gain! */
> >> +		unsigned int idx;
> >> +		idx = std::min({ i * gains.red / div, kGammaLookupSize - 1 });
> >> +		params->red[i] = gammaTable[idx];
> >> +		idx = std::min({ i * gains.green / div, kGammaLookupSize - 1 });
> >> +		params->green[i] = gammaTable[idx];
> >> +		idx = std::min({ i * gains.blue / div, kGammaLookupSize - 1 });
> >> +		params->blue[i] = gammaTable[idx];
> >> +	}
> >
> > Why is this a separate algorithm, why isn't it part of Gamma ?
> 
> Well, constructing the gamma table and the color lookup tables are two
> different things.  While the gammaTable looks like a utility just for
> the color lookup tables here, it may not always be the case, for
> instance contrast adjustment may be implemented by modifying the gamma
> table. 
> 
> But I don't have a strong opinion on this and I can merge the two.

I'd start simple and merge the two, and split them later if needed.

> >> +}
> >> +
> >> +REGISTER_IPA_ALGORITHM(Lut, "Lut")
> >> +
> >> +} /* namespace ipa::soft::algorithms */
> >> +
> >> +} /* namespace libcamera */
> >> diff --git a/src/ipa/simple/algorithms/lut.h b/src/ipa/simple/algorithms/lut.h
> >> new file mode 100644
> >> index 00000000..5b5e554e
> >> --- /dev/null
> >> +++ b/src/ipa/simple/algorithms/lut.h
> >> @@ -0,0 +1,37 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2024, Red Hat Inc.
> >> + *
> >> + * Lookup table construction
> >> + */
> >> +
> >> +#pragma once
> >> +
> >> +#include <libcamera/controls.h>
> >> +
> >> +#include "libcamera/internal/software_isp/debayer_params.h"
> >> +
> >> +#include "algorithm.h"
> >> +#include "ipa_context.h"
> >> +
> >> +namespace libcamera {
> >> +
> >> +namespace ipa::soft::algorithms {
> >> +
> >> +class Lut : public Algorithm
> >> +{
> >> +public:
> >> +	Lut() = default;
> >> +	~Lut() = default;
> >> +
> >> +	int init(IPAContext &context, const YamlObject &tuningData)
> >> +		override;
> >> +	void prepare(IPAContext &context,
> >> +		     const uint32_t frame,
> >> +		     IPAFrameContext &frameContext,
> >> +		     DebayerParams *params) override;
> >> +};
> >> +
> >> +} /* namespace ipa::soft::algorithms */
> >> +
> >> +} /* namespace libcamera */
> >> diff --git a/src/ipa/simple/algorithms/meson.build b/src/ipa/simple/algorithms/meson.build
> >> index 1f63c220..68e5aa58 100644
> >> --- a/src/ipa/simple/algorithms/meson.build
> >> +++ b/src/ipa/simple/algorithms/meson.build
> >> @@ -1,5 +1,8 @@
> >>  # SPDX-License-Identifier: CC0-1.0
> >>  
> >>  soft_simple_ipa_algorithms = files([
> >> +    'awb.cpp',
> >>      'blc.cpp',
> >> +    'gamma.cpp',
> >> +    'lut.cpp',
> >>  ])
> >> diff --git a/src/ipa/simple/data/uncalibrated.yaml b/src/ipa/simple/data/uncalibrated.yaml
> >> index e0d03d96..deaea6b1 100644
> >> --- a/src/ipa/simple/data/uncalibrated.yaml
> >> +++ b/src/ipa/simple/data/uncalibrated.yaml
> >> @@ -4,4 +4,7 @@
> >>  version: 1
> >>  algorithms:
> >>    - BlackLevel:
> >> +  - Gamma:
> >> +  - Awb:
> >> +  - Lut:
> >>  ...
> >> diff --git a/src/ipa/simple/ipa_context.cpp b/src/ipa/simple/ipa_context.cpp
> >> index 268cff32..5fa492cb 100644
> >> --- a/src/ipa/simple/ipa_context.cpp
> >> +++ b/src/ipa/simple/ipa_context.cpp
> >> @@ -50,6 +50,11 @@ namespace libcamera::ipa::soft {
> >>   * \brief The current state of IPA algorithms
> >>   */
> >>  
> >> +/**
> >> + * \var IPASessionConfiguration::gamma
> >> + * \brief Gamma value to be used in the raw image processing
> >> + */
> >> +
> >>  /**
> >>   * \var IPAActiveState::black
> >>   * \brief Context for the Black Level algorithm
> >> @@ -58,4 +63,29 @@ namespace libcamera::ipa::soft {
> >>   * \brief Current determined black level
> >>   */
> >>  
> >> +/**
> >> + * \var IPAActiveState::gains
> >> + * \brief Context for gains in the Colors algorithm
> >> + *
> >> + * \var IPAActiveState::gains.red
> >> + * \brief Gain of red color
> >> + *
> >> + * \var IPAActiveState::gains.green
> >> + * \brief Gain of green color
> >> + *
> >> + * \var IPAActiveState::gains.blue
> >> + * \brief Gain of blue color
> >> + */
> >> +
> >> +/**
> >> + * \var IPAActiveState::gamma
> >> + * \brief Context for gamma in the Colors algorithm
> >> + *
> >> + * \var IPAActiveState::gamma.gammaTable
> >> + * \brief Computed gamma table
> >> + *
> >> + * \var IPAActiveState::gamma.blackLevel
> >> + * \brief Black level used for the gamma table computation
> >> + */
> >> +
> >>  } /* namespace libcamera::ipa::soft */
> >> diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
> >> index 22156569..f8b8834d 100644
> >> --- a/src/ipa/simple/ipa_context.h
> >> +++ b/src/ipa/simple/ipa_context.h
> >> @@ -7,6 +7,7 @@
> >>  
> >>  #pragma once
> >>  
> >> +#include <array>
> >>  #include <stdint.h>
> >>  
> >>  #include <libipa/fc_queue.h>
> >> @@ -16,12 +17,23 @@ namespace libcamera {
> >>  namespace ipa::soft {
> >>  
> >>  struct IPASessionConfiguration {
> >> +	float gamma;
> >>  };
> >>  
> >>  struct IPAActiveState {
> >>  	struct {
> >>  		uint8_t level;
> >>  	} black;
> >
> > Blank line. Same below.
> >
> >> +	struct {
> >> +		unsigned int red;
> >> +		unsigned int green;
> >> +		unsigned int blue;
> >> +	} gains;
> >> +	static constexpr unsigned int kGammaLookupSize = 1024;
> >
> > This duplicates the kGammaLookupSize from
> > src/ipa/simple/algorithms/gamma.h. 
> 
> Yes.  The constant in gamma.h is actually not needed when replacing it
> with size() calls, I'll remove it.
> 
> >> +	struct {
> >> +		std::array<double, kGammaLookupSize> gammaTable;
> >> +		uint8_t blackLevel;
> >> +	} gamma;
> >>  };
> >>  
> >>  struct IPAFrameContext : public FrameContext {
> >> diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp
> >> index a1bd2f0c..8f01bf7d 100644
> >> --- a/src/ipa/simple/soft_simple.cpp
> >> +++ b/src/ipa/simple/soft_simple.cpp
> >> @@ -5,8 +5,6 @@
> >>   * Simple Software Image Processing Algorithm module
> >>   */
> >>  
> >> -#include <cmath>
> >> -#include <numeric>
> >>  #include <stdint.h>
> >>  #include <sys/mman.h>
> >>  
> >> @@ -93,9 +91,6 @@ private:
> >>  	std::unique_ptr<CameraSensorHelper> camHelper_;
> >>  	ControlInfoMap sensorInfoMap_;
> >>  
> >> -	static constexpr unsigned int kGammaLookupSize = 1024;
> >> -	std::array<uint8_t, kGammaLookupSize> gammaTable_;
> >> -	int lastBlackLevel_ = -1;
> >>  	/* Local parameter storage */
> >>  	struct IPAContext context_;
> >>  
> >> @@ -283,6 +278,7 @@ void IPASoftSimple::prepare(const uint32_t frame)
> >>  	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
> >>  	for (auto const &algo : algorithms())
> >>  		algo->prepare(context_, frame, frameContext, params_);
> >> +	setIspParams.emit();
> >>  }
> >>  
> >>  void IPASoftSimple::processStats(const uint32_t frame,
> >> @@ -300,62 +296,6 @@ void IPASoftSimple::processStats(const uint32_t frame,
> >>  	for (auto const &algo : algorithms())
> >>  		algo->process(context_, frame, frameContext, stats_, metadata);
> >>  
> >> -	SwIspStats::Histogram histogram = stats_->yHistogram;
> >> -	const uint8_t blackLevel = context_.activeState.black.level;
> >> -
> >> -	/*
> >> -	 * Black level must be subtracted to get the correct AWB ratios, they
> >> -	 * would be off if they were computed from the whole brightness range
> >> -	 * rather than from the sensor range.
> >> -	 */
> >> -	const uint64_t nPixels = std::accumulate(
> >> -		histogram.begin(), histogram.end(), 0);
> >> -	const uint64_t offset = blackLevel * nPixels;
> >> -	const uint64_t sumR = stats_->sumR_ - offset / 4;
> >> -	const uint64_t sumG = stats_->sumG_ - offset / 2;
> >> -	const uint64_t sumB = stats_->sumB_ - offset / 4;
> >> -
> >> -	/*
> >> -	 * Calculate red and blue gains for AWB.
> >> -	 * Clamp max gain at 4.0, this also avoids 0 division.
> >> -	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
> >> -	 */
> >> -	const unsigned int gainR = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
> >> -	const unsigned int gainB = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
> >> -	/* Green gain and gamma values are fixed */
> >> -	constexpr unsigned int gainG = 256;
> >> -
> >> -	/* Update the gamma table if needed */
> >> -	if (blackLevel != lastBlackLevel_) {
> >> -		constexpr float gamma = 0.5;
> >> -		const unsigned int blackIndex = blackLevel * kGammaLookupSize / 256;
> >> -		std::fill(gammaTable_.begin(), gammaTable_.begin() + blackIndex, 0);
> >> -		const float divisor = kGammaLookupSize - blackIndex - 1.0;
> >> -		for (unsigned int i = blackIndex; i < kGammaLookupSize; i++)
> >> -			gammaTable_[i] = UINT8_MAX *
> >> -					 std::pow((i - blackIndex) / divisor, gamma);
> >> -
> >> -		lastBlackLevel_ = blackLevel;
> >> -	}
> >> -
> >> -	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
> >> -		constexpr unsigned int div =
> >> -			DebayerParams::kRGBLookupSize * 256 / kGammaLookupSize;
> >> -		unsigned int idx;
> >> -
> >> -		/* Apply gamma after gain! */
> >> -		idx = std::min({ i * gainR / div, (kGammaLookupSize - 1) });
> >> -		params_->red[i] = gammaTable_[idx];
> >> -
> >> -		idx = std::min({ i * gainG / div, (kGammaLookupSize - 1) });
> >> -		params_->green[i] = gammaTable_[idx];
> >> -
> >> -		idx = std::min({ i * gainB / div, (kGammaLookupSize - 1) });
> >> -		params_->blue[i] = gammaTable_[idx];
> >> -	}
> >> -
> >> -	setIspParams.emit();
> >> -
> >>  	/* \todo Switch to the libipa/algorithm.h API someday. */
> >>  
> >>  	/*
> >> @@ -372,6 +312,7 @@ void IPASoftSimple::processStats(const uint32_t frame,
> >>  	 * Calculate Mean Sample Value (MSV) according to formula from:
> >>  	 * https://www.araa.asn.au/acra/acra2007/papers/paper84final.pdf
> >>  	 */
> >> +	const uint8_t blackLevel = context_.activeState.black.level;
> >>  	const unsigned int blackLevelHistIdx =
> >>  		blackLevel / (256 / SwIspStats::kYHistogramSize);
> >>  	const unsigned int histogramSize =
> >> @@ -421,7 +362,8 @@ void IPASoftSimple::processStats(const uint32_t frame,
> >>  
> >>  	LOG(IPASoft, Debug) << "exposureMSV " << exposureMSV
> >>  			    << " exp " << exposure_ << " again " << again_
> >> -			    << " gain R/B " << gainR << "/" << gainB
> >> +			    << " gain R/B " << context_.activeState.gains.red
> >> +			    << "/" << context_.activeState.gains.blue
> >
> > That's already printed in Awb::process(), does it need to be duplicated
> > here ?
> 
> I don't think so, I'll remove it here.
> 
> >>  			    << " black level " << static_cast<unsigned int>(blackLevel);
> >>  }
> >>