[PATCH 2/3] ipa: libipa: Add MatrixInterpolator class

[Paul Elder]

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.

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
---
 src/ipa/libipa/matrix_interpolator.cpp | 54 +++++++++++++++
 src/ipa/libipa/matrix_interpolator.h   | 94 ++++++++++++++++++++++++++
 src/ipa/libipa/meson.build             |  2 +
 3 files changed, 150 insertions(+)
 create mode 100644 src/ipa/libipa/matrix_interpolator.cpp
 create mode 100644 src/ipa/libipa/matrix_interpolator.h

diff --git a/src/ipa/libipa/matrix_interpolator.cpp b/src/ipa/libipa/matrix_interpolator.cpp
new file mode 100644
index 00000000..394633b5
--- /dev/null
+++ b/src/ipa/libipa/matrix_interpolator.cpp
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi Ltd
+ * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
+ *
+ * matrix_interpolator.cpp - 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 ccm.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
+ */
+
+/**
+ * \fn int MatrixInterpolator<T, R, C>::readYaml(const libcamera::YamlObject &yaml)
+ * \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
+ * \return Zero on success, negative error code otherwise
+ */
+
+/**
+ * \fn Matrix<T> 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..2cd4ff75
--- /dev/null
+++ b/src/ipa/libipa/matrix_interpolator.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi Ltd
+ * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
+ *
+ * matrix_interpolator.h - 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 {
+
+template<typename T, unsigned int R, unsigned int C>
+class MatrixInterpolator
+{
+public:
+	MatrixInterpolator(){};
+	~MatrixInterpolator(){};
+
+	int readYaml(const libcamera::YamlObject &yaml)
+	{
+		int ret;
+
+		if (!yaml.isDictionary()) {
+			LOG(MatrixInterpolator, Error) << "yaml object must be a dictionary";
+			return -EINVAL;
+		}
+
+		for (const auto &[ctStr, value] : yaml.asDict()) {
+			unsigned int ct = std::stoul(ctStr);
+			Matrix<T> matrix;
+			if ((ret = matrix.readYaml(R, C, value)) < 0) {
+				LOG(MatrixInterpolator, Error) << "Failed to read matrix";
+				return ret;
+			}
+
+			matrices_[ct] = matrix;
+
+			LOG(MatrixInterpolator, Debug)
+				<< "Read matrix for key " << ct << ": "
+				<< matrices_[ct].toString();
+		}
+
+		if (matrices_.size() < 1) {
+			LOG(MatrixInterpolator, Error) << "Need at least one matrix";
+			return -EINVAL;
+		}
+
+		return 0;
+	}
+
+	Matrix<T> get(unsigned int ct)
+	{
+		if (matrices_.size() == 1 ||
+		    ct <= matrices_.begin()->first)
+			return matrices_.begin()->second;
+
+		if (ct >= matrices_.rbegin()->first)
+			return matrices_.rbegin()->second;
+
+		if (matrices_.count(ct))
+			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) / (ctUpper - ctLower);
+		return lambda * matrices_[ctUpper] + (1.0 - lambda) * matrices_[ctLower];
+	}
+
+private:
+	std::map<unsigned int, Matrix<T>> matrices_;
+};
+
+} /* namespace ipa */
+
+} /* namespace libcamera */
diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
index 5d5ba5e5..128de712 100644
--- a/src/ipa/libipa/meson.build
+++ b/src/ipa/libipa/meson.build
@@ -3,6 +3,7 @@
 libipa_headers = files([
     'algorithm.h',
     'camera_sensor_helper.h',
+    'matrix_interpolator.h',
     'exposure_mode_helper.h',
     'fc_queue.h',
     'histogram.h',
@@ -14,6 +15,7 @@ libipa_headers = files([
 libipa_sources = files([
     'algorithm.cpp',
     'camera_sensor_helper.cpp',
+    'matrix_interpolator.cpp',
     'exposure_mode_helper.cpp',
     'fc_queue.cpp',
     'histogram.cpp',
-- 
2.39.2