new file mode 100644
@@ -0,0 +1,157 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Paul Elder <paul.elder@ideasonboard.com>
+ *
+ * Helper class for interpolating objects
+ */
+#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 an empty interpolator
+ */
+
+/**
+ * \fn Interpolator::Interpolator(const std::map<unsigned int, T> &data)
+ * \brief Construct an interpolator from a map of objects
+ * \param data Map from which to construct the interpolator
+ */
+
+/**
+ * \fn Interpolator::Interpolator(std::map<unsigned int, T> &&data)
+ * \brief Construct an 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 value 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 Interpolator<T>::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
+ * updates 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 Interpolator<T>::setData(std::map<unsigned int, T> &&data)
+ * \brief Set the internal map
+ *
+ * Overwrites the internal map using move semantics.
+ */
+
+/**
+ * \fn const T& Interpolator<T>::getInterpolated()
+ * \brief Retrieve an 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.
+ */
+
+/**
+ * \fn void Interpolator<T>::interpolate(const T &a, const T &b, T &dest, double
+ * lambda)
+ * \brief Interpolate between two instances of T
+ * \param a The first value to interpolate
+ * \param b The second value to interpolate
+ * \param dest The destination for the interpolated value
+ * \param lambda The interpolation factor (0..1)
+ *
+ * Interpolates between \a a and \a b according to \a lambda. It calculates
+ * dest = a * (1.0 - lambda) + b * lambda;
+ *
+ * If T supports multiplication with double and addition, this function can be
+ * used as is. For other types this function can be overwritten using partial
+ * template specialization.
+ */
+
+} /* namespace ipa */
+
+} /* namespace libcamera */
new file mode 100644
@@ -0,0 +1,131 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Paul Elder <paul.elder@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() = default;
+ Interpolator(const std::map<unsigned int, T> &data)
+ : data_(data)
+ {
+ }
+ Interpolator(std::map<unsigned int, T> &&data)
+ : data_(std::move(data))
+ {
+ }
+
+ ~Interpolator() = default;
+
+ int readYaml(const libcamera::YamlObject &yaml,
+ const std::string &key_name,
+ const std::string &value_name)
+ {
+ data_.clear();
+ lastInterpolatedKey_.reset();
+
+ 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);
+ lastInterpolatedKey_.reset();
+ }
+
+ 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_;
+
+ 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);
+ interpolate(it2->second, it->second, lastInterpolatedValue_, lambda);
+ lastInterpolatedKey_ = key;
+
+ 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_ = 0;
+};
+
+} /* namespace ipa */
+
+} /* namespace libcamera */
@@ -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',