[PATCH v1 1/8] ipa: libipa: Add generic Interpolator class

[Barnabás Pőcze]

Hi


2024. augusztus 26., hétfő 18:21 keltezéssel, Stefan Klug <stefan.klug at ideasonboard.com> írta:

> The MatrixInterpolator is great for interpolation of matrices for different
> color temperatures. It has however one limitation - it can only handle
> matrices. For LSC it would be great to interpolate the LSC tables (or even
> polynomials) using the same approach. Add a generic Interpolator class based on
> the existing MatrixInterpolator. This calss can be adapted to any other type
> using partial template specialization.
> 
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
>  src/ipa/libipa/interpolator.cpp | 139 ++++++++++++++++++++++++++++++++
>  src/ipa/libipa/interpolator.h   | 139 ++++++++++++++++++++++++++++++++
>  src/ipa/libipa/meson.build      |   2 +
>  3 files changed, 280 insertions(+)
>  create mode 100644 src/ipa/libipa/interpolator.cpp
>  create mode 100644 src/ipa/libipa/interpolator.h
> 
> diff --git a/src/ipa/libipa/interpolator.cpp b/src/ipa/libipa/interpolator.cpp
> new file mode 100644
> index 000000000000..98462d1509da
> --- /dev/null
> +++ b/src/ipa/libipa/interpolator.cpp
> @@ -0,0 +1,139 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> + *
> + * Helper class for interpolating maps of matrices
> + */
> +#include "interpolator.h"
> +
> +#include <algorithm>
> +#include <string>
> +
> +#include <libcamera/base/log.h>
> +
> +#include "libcamera/internal/yaml_parser.h"
> +
> +#include "interpolator.h"
> +
> +/**
> + * \file interpolator.h
> + * \brief Helper class for linear interpolating a set of objects
> + */
> +
> +namespace libcamera {
> +
> +LOG_DEFINE_CATEGORY(Interpolator)
> +
> +namespace ipa {
> +
> +/**
> + * \class Interpolator
> + * \brief Class for storing, retrieving, and interpolating objects
> + * \tparam T Type of objects stored in the interpolator
> + *
> + * The main use case is to pass a map from color temperatures to corresponding
> + * objects (eg. matrices for color correction), and then requesting a
> + * interpolated object for a specific color temperature. This class will
> + * abstract away the interpolation portion.
> + */
> +
> +/**
> + * \fn Interpolator::Interpolator()
> + * \brief Construct a empty interpolator
> + */
> +
> +/**
> + * \fn Interpolator::Interpolator(const std::map<unsigned int, T> &data)
> + * \brief Construct a interpolator from a map of objects
> + * \param data Map from which to construct the interpolator
> + */
> +
> +/**
> + * \fn Interpolator::Interpolator(const std::map<unsigned int, T> &&data)
> + * \brief Construct a interpolator from a map of objects
> + * \param data Map from which to construct the interpolator
> + */
> +
> +/**
> + * \fn int Interpolator<T>::readYaml(const libcamera::YamlObject &yaml,
> +		                     const std::string &key_name,
> +		                     const std::string &value_name)
> + * \brief Initialize an Interpolator instance from yaml
> + * \tparam T Type of data stored in the interpolator
> + * \param[in] yaml The yaml object that contains the map of unsigned integers to objects
> + * \param[in] key_name The name of the key in the yaml object
> + * \param[in] value_name The name of the matrix in the yaml object
> + *
> + * The yaml object is expected to be a list of maps. Each map has two or more
> + * pairs: one of \a key_name to the key value (usually color temperature), and
> + * one or more of \a value_name to the object. This is a bit difficult to
> + * explain, so here is an example (in python, as it is easier to parse than
> + * yaml):
> + *       [
> + *               {
> + *                   'ct': 2860,
> + *                   'ccm': [ 2.12089, -0.52461, -0.59629,
> + *                           -0.85342,  2.80445, -0.95103,
> + *                           -0.26897, -1.14788,  2.41685 ],
> + *                   'offsets': [ 0, 0, 0 ]
> + *               },
> + *
> + *               {
> + *                   'ct': 2960,
> + *                   'ccm': [ 2.26962, -0.54174, -0.72789,
> + *                           -0.77008,  2.60271, -0.83262,
> + *                           -0.26036, -1.51254,  2.77289 ],
> + *                   'offsets': [ 0, 0, 0 ]
> + *               },
> + *
> + *               {
> + *                   'ct': 3603,
> + *                   'ccm': [ 2.18644, -0.66148, -0.52496,
> + *                           -0.77828,  2.69474, -0.91645,
> + *                           -0.25239, -0.83059,  2.08298 ],
> + *                   'offsets': [ 0, 0, 0 ]
> + *               },
> + *       ]
> + *
> + * In this case, \a key_name would be 'ct', and \a value_name can be either
> + * 'ccm' or 'offsets'. This way multiple interpolators can be defined in
> + * one set of color temperature ranges in the tuning file, and they can be
> + * retrieved separately with the \a value_name parameter.
> + *
> + * \return Zero on success, negative error code otherwise
> + */
> +
> +/**
> + * \fn void setQuantization(const unsigned int q)
> + * \brief Set the quantization value
> + * \param[in] q The quantization value
> + *
> + * Sets the quantization value. When this is set key gets quantized to this size,
> + * before doing the interpolation. This can help in reducing the number of
> + * updated pushed to the hardware.
> + *
> + * Note that normally a threshold needs to be combined with quantization.
> + * Otherwise a value that swings around the edge of the quantization step will
> + * lead to constant updates.
> + */
> +
> +/**
> + * \fn void setData(std::map<unsigned int, T> &&data)
> + * \brief Set the internal map
> + *
> + * Overwrites the internal map using move semantics.
> + */
> +
> +/**
> + * \fn const T &getInterpolated(unsigned int key, unsigned int *quantizedKey = nullptr)
> + * \brief Retrieve a a interpolated value for the given key
> + * \param[in] key The unsigned integer key of the object to retrieve
> + * \param[out] quantizedKey If provided, the key value after quantization
> + * \return The object corresponding to the key. The object is cached internally,
> + * so on successive calls with the same key (after quantization) interpolation
> + * is not recalculated.
> + */
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/interpolator.h b/src/ipa/libipa/interpolator.h
> new file mode 100644
> index 000000000000..b0241c35bbab
> --- /dev/null
> +++ b/src/ipa/libipa/interpolator.h
> @@ -0,0 +1,139 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> + *
> + * Helper class for interpolating maps of objects
> + */
> +
> +#pragma once
> +
> +#include <algorithm>
> +#include <cmath>
> +#include <map>
> +#include <string>
> +#include <tuple>
> +
> +#include <libcamera/base/log.h>
> +
> +#include "libcamera/internal/yaml_parser.h"
> +
> +namespace libcamera {
> +
> +LOG_DECLARE_CATEGORY(Interpolator)
> +
> +namespace ipa {
> +
> +template<typename T>
> +class Interpolator
> +{
> +public:
> +	Interpolator()
> +	{
> +		quantization_ = 0;
> +	}

Interpolator() = default;


> +
> +	Interpolator(const std::map<unsigned int, T> &data)
> +	{
> +		quantization_ = 0;
> +		data_ = data;
> +	}

Interpolator(const std::map<unsigned int, T> &data)
	: data_(data)
{ }


> +
> +	Interpolator(std::map<unsigned int, T> &&data)
> +	{
> +		quantization_ = 0;
> +		data_ = std::move(data);
> +	}

Interpolator(std::map<unsigned int, T> &&data)
	: data_(std::move(data))
{ }


> +
> +	~Interpolator() {}

~Interpolator() = default;


> +
> +	int readYaml(const libcamera::YamlObject &yaml,
> +		     const std::string &key_name,
> +		     const std::string &value_name)
> +	{
> +		data_.clear();
> +
> +		if (!yaml.isList()) {
> +			LOG(Interpolator, Error) << "yaml object must be a list";
> +			return -EINVAL;
> +		}
> +
> +		for (const auto &value : yaml.asList()) {
> +			unsigned int ct = std::stoul(value[key_name].get<std::string>(""));
> +			std::optional<T> data =
> +				value[value_name].get<T>();
> +			if (!data) {
> +				return -EINVAL;
> +			}
> +
> +			data_[ct] = *data;
> +		}
> +
> +		if (data_.size() < 1) {
> +			LOG(Interpolator, Error) << "Need at least one element";
> +			return -EINVAL;
> +		}
> +
> +		return 0;
> +	}
> +
> +	void setQuantization(const unsigned int q)
> +	{
> +		quantization_ = q;
> +	}
> +
> +	void setData(std::map<unsigned int, T> &&data)
> +	{
> +		data_ = std::move(data);
> +	}
> +
> +	const T &getInterpolated(unsigned int key, unsigned int *quantizedKey = nullptr)
> +	{
> +		ASSERT(data_.size() > 0);
> +
> +		if (quantization_ > 0)
> +			key = std::lround(key / static_cast<double>(quantization_)) * quantization_;
> +
> +		if (quantizedKey)
> +			*quantizedKey = key;
> +
> +		if (lastInterpolatedKey_.has_value() &&
> +		    *lastInterpolatedKey_ == key)
> +			return lastInterpolatedValue_;

setData() should reset the cache. By the way, is caching worth it?


> +
> +		if (data_.size() == 1 ||
> +		    key <= data_.begin()->first)
> +			return data_.begin()->second;
> +
> +		if (key >= data_.rbegin()->first)
> +			return data_.rbegin()->second;
> +
> +		if (data_.find(key) != data_.end())
> +			return data_[key];
> +
> +		/* The above four guarantee that this will succeed */
> +		auto iter = data_.upper_bound(key);
> +		unsigned int ctUpper = iter->first;
> +		unsigned int ctLower = (--iter)->first;
> +
> +		double lambda = (key - ctLower) / static_cast<double>(ctUpper - ctLower);
> +		interpolate(data_[ctLower], data_[ctUpper], lastInterpolatedValue_, lambda);
> +		lastInterpolatedKey_ = key;

The above has 5 separate map lookups, I am wondering if something like this could work:

  auto it = data_.lower_bound(key);

  if (it == data_.begin())
    return it->second;

  if (it == data_.end())
    return std::prev(it)->second;

  if (it->first == key)
    return it->second;

  auto it2 = std::prev(it);

  double lambda = (key - it2->first) / static_cast<double>(it->first - it2->first);
  T val = it2->second * (1 - lambda) + it->second * lambda;


> +
> +		return lastInterpolatedValue_;
> +	}
> +
> +	void interpolate(const T &a, const T &b, T &dest, double lambda)
> +	{
> +		dest = a * (1.0 - lambda) + b * lambda;
> +	}
> +
> +private:
> +	std::map<unsigned int, T> data_;
> +	T lastInterpolatedValue_;
> +	std::optional<unsigned int> lastInterpolatedKey_;
> +	unsigned int quantization_;

Since `quantization_` is initialized to 0 in all constructors, I think it might
be best to say ` = 0` here.


Regards,
Barnabás Pőcze


> +};
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> index eff8ce2660f1..2c2712a7d252 100644
> --- a/src/ipa/libipa/meson.build
> +++ b/src/ipa/libipa/meson.build
> @@ -7,6 +7,7 @@ libipa_headers = files([
>      'exposure_mode_helper.h',
>      'fc_queue.h',
>      'histogram.h',
> +    'interpolator.h',
>      'matrix.h',
>      'matrix_interpolator.h',
>      'module.h',
> @@ -21,6 +22,7 @@ libipa_sources = files([
>      'exposure_mode_helper.cpp',
>      'fc_queue.cpp',
>      'histogram.cpp',
> +    'interpolator.cpp',
>      'matrix.cpp',
>      'matrix_interpolator.cpp',
>      'module.cpp',
> --
> 2.43.0
> 
>