ipa: libipa: Add MatrixInterpolator class

Add a class to encapsulate the functionality of fetching a matrix based
on an integer key, and interpolating if there is no exact match. This is
expected to be used by both color correction matrices / crosstalk
correction as well as lens shading correction.

A cache is included only for exact matches of the key. The caller is
expected to decide the tolererance for rounding.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

3 files changed, 234 insertions, 0 deletions

diff --git a/src/ipa/libipa/matrix_interpolator.cpp b/src/ipa/libipa/matrix_interpolator.cpp
new file mode 100644
index 00000000..04ca177f
--- /dev/null
+++ b/src/ipa/libipa/matrix_interpolator.cpp
@@ -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 */
diff --git a/src/ipa/libipa/matrix_interpolator.h b/src/ipa/libipa/matrix_interpolator.h
new file mode 100644
index 00000000..087c4fd1
--- /dev/null
+++ b/src/ipa/libipa/matrix_interpolator.h
@@ -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 */
diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
index 1952dccf..eff8ce26 100644
--- a/src/ipa/libipa/meson.build
+++ b/src/ipa/libipa/meson.build
@@ -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',