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>

1 files changed, 122 insertions, 0 deletions

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 */