new file mode 100644
@@ -0,0 +1,110 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Paul Elder <paul.elder@ideasonboard.com>
+ *
+ * Helper class for interpolating maps of matrices
+ */
+#include "matrix_interpolator.h"
+
+#include <algorithm>
+#include <string>
+
+#include <libcamera/base/log.h>
+
+#include "libcamera/internal/yaml_parser.h"
+
+#include "matrix.h"
+
+/**
+ * \file matrix_interpolator.h
+ * \brief Helper class for interpolating maps of matrices
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(MatrixInterpolator)
+
+namespace ipa {
+
+/**
+ * \class MatrixInterpolator
+ * \brief Class for storing, retrieving, and interpolating matrices
+ * \tparam T Type of numerical values to be stored in the matrices
+ * \tparam R Number of rows in the matrices
+ * \tparam C Number of columns in the matrices
+ *
+ * The main use case is to pass a map from color temperatures to corresponding
+ * matrices (eg. color correction), and then requesting a matrix for a specific
+ * color temperature. This class will abstract away the interpolation portion.
+ */
+
+/**
+ * \fn MatrixInterpolator::MatrixInterpolator(const std::map<unsigned int, Matrix<T, R, C>> &matrices)
+ * \brief Construct a matrix interpolator from a map of matrices
+ * \param matrices Map from which to construct the matrix interpolator
+ */
+
+/**
+ * \fn MatrixInterpolator::reset()
+ * \brief Reset the matrix interpolator content to a single identity matrix
+ */
+
+/**
+ * \fn int MatrixInterpolator<T, R, C>::readYaml()
+ * \brief Initialize an MatrixInterpolator instance from yaml
+ * \tparam T Type of data stored in the matrices
+ * \tparam R Number of rows of the matrices
+ * \tparam C Number of columns of the matrices
+ * \param[in] yaml The yaml object that contains the map of unsigned integers to matrices
+ * \param[in] key_name The name of the key in the yaml object
+ * \param[in] matrix_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 matrix_name to the matrix. 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 matrix_name can be either
+ * 'ccm' or 'offsets'. This way multiple matrix interpolators can be defined in
+ * one set of color temperature ranges in the tuning file, and they can be
+ * retrieved separately with the \a matrix_name parameter.
+ *
+ * \return Zero on success, negative error code otherwise
+ */
+
+/**
+ * \fn Matrix<T, R, C> MatrixInterpolator<T, R, C>::get(unsigned int key)
+ * \brief Retrieve a matrix from the list of matrices, interpolating if necessary
+ * \param[in] key The unsigned integer key of the matrix to retrieve
+ * \return The matrix corresponding to the color temperature
+ */
+
+} /* namespace ipa */
+
+} /* namespace libcamera */
new file mode 100644
@@ -0,0 +1,122 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Paul Elder <paul.elder@ideasonboard.com>
+ *
+ * Helper class for interpolating maps of matrices
+ */
+
+#pragma once
+
+#include <algorithm>
+#include <map>
+#include <string>
+#include <tuple>
+
+#include <libcamera/base/log.h>
+
+#include "libcamera/internal/yaml_parser.h"
+
+#include "matrix.h"
+
+namespace libcamera {
+
+LOG_DECLARE_CATEGORY(MatrixInterpolator)
+
+namespace ipa {
+
+#ifndef __DOXYGEN__
+template<typename T, unsigned int R, unsigned int C,
+ std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
+#else
+template<typename T, unsigned int R, unsigned int C>
+#endif /* __DOXYGEN__ */
+class MatrixInterpolator
+{
+public:
+ MatrixInterpolator()
+ {
+ reset();
+ }
+
+ MatrixInterpolator(const std::map<unsigned int, Matrix<T, R, C>> &matrices)
+ {
+ for (const auto &pair : matrices)
+ matrices_[pair.first] = pair.second;
+ }
+
+ ~MatrixInterpolator() {}
+
+ void reset()
+ {
+ matrices_.clear();
+ matrices_[0] = Matrix<T, R, C>::identity();
+ }
+
+ int readYaml(const libcamera::YamlObject &yaml,
+ const std::string &key_name,
+ const std::string &matrix_name)
+ {
+ matrices_.clear();
+
+ if (!yaml.isList()) {
+ LOG(MatrixInterpolator, 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<Matrix<T, R, C>> matrix =
+ value[matrix_name].get<Matrix<T, R, C>>();
+ if (!matrix) {
+ LOG(MatrixInterpolator, Error) << "Failed to read matrix";
+ return -EINVAL;
+ }
+
+ matrices_[ct] = *matrix;
+
+ LOG(MatrixInterpolator, Debug)
+ << "Read matrix '" << matrix_name << "' for key '"
+ << key_name << "' " << ct << ": "
+ << matrices_[ct].toString();
+ }
+
+ if (matrices_.size() < 1) {
+ LOG(MatrixInterpolator, Error) << "Need at least one matrix";
+ return -EINVAL;
+ }
+
+ return 0;
+ }
+
+ Matrix<T, R, C> get(unsigned int ct)
+ {
+ ASSERT(matrices_.size() > 0);
+
+ if (matrices_.size() == 1 ||
+ ct <= matrices_.begin()->first)
+ return matrices_.begin()->second;
+
+ if (ct >= matrices_.rbegin()->first)
+ return matrices_.rbegin()->second;
+
+ if (matrices_.find(ct) != matrices_.end())
+ return matrices_[ct];
+
+ /* The above four guarantee that this will succeed */
+ auto iter = matrices_.upper_bound(ct);
+ unsigned int ctUpper = iter->first;
+ unsigned int ctLower = (--iter)->first;
+
+ double lambda = (ct - ctLower) / static_cast<double>(ctUpper - ctLower);
+ Matrix<T, R, C> ret =
+ lambda * matrices_[ctUpper] + (1.0 - lambda) * matrices_[ctLower];
+ return ret;
+ }
+
+private:
+ std::map<unsigned int, Matrix<T, R, C>> matrices_;
+};
+
+} /* namespace ipa */
+
+} /* namespace libcamera */
@@ -8,6 +8,7 @@ libipa_headers = files([
'fc_queue.h',
'histogram.h',
'matrix.h',
+ 'matrix_interpolator.h',
'module.h',
'pwl.h',
'vector.h',
@@ -21,6 +22,7 @@ libipa_sources = files([
'fc_queue.cpp',
'histogram.cpp',
'matrix.cpp',
+ 'matrix_interpolator.cpp',
'module.cpp',
'pwl.cpp',
'vector.cpp',