ipa: libipa: Copy pwl from rpi, and clean it up to match libcamera

Copy the piecewise linear function code from Raspberry Pi,
and clean it up to align it more with the libcamera style.

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

1 files changed, 86 insertions, 0 deletions

diff --git a/src/ipa/libipa/pwl.h b/src/ipa/libipa/pwl.h
new file mode 100644
index 00000000..4cc257f9
--- /dev/null
+++ b/src/ipa/libipa/pwl.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi Ltd
+ *
+ * Piecewise linear functions interface
+ */
+#pragma once
+
+#include <algorithm>
+#include <cmath>
+#include <functional>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "libcamera/internal/yaml_parser.h"
+
+#include "vector.h"
+
+namespace libcamera {
+
+namespace ipa {
+
+class Pwl
+{
+public:
+	using Point = Vector<double, 2>;
+
+	struct Interval {
+		Interval(double _start, double _end)
+			: start(_start), end(_end) {}
+
+		bool contains(double value)
+		{
+			return value >= start && value <= end;
+		}
+
+		double clamp(double value)
+		{
+			return std::clamp(value, start, end);
+		}
+
+		double length() const { return end - start; }
+
+		double start, end;
+	};
+
+	Pwl();
+	Pwl(const std::vector<Point> &points);
+	int readYaml(const libcamera::YamlObject &params);
+
+	void append(double x, double y, double eps = 1e-6);
+
+	bool empty() const;
+	Interval domain() const;
+	Interval range() const;
+
+	double eval(double x, int *span = nullptr,
+		    bool updateSpan = true) const;
+
+	std::pair<Pwl, bool> inverse(double eps = 1e-6) const;
+	Pwl compose(const Pwl &other, double eps = 1e-6) const;
+
+	void map(std::function<void(double x, double y)> f) const;
+
+	static Pwl
+	combine(const Pwl &pwl0, const Pwl &pwl1,
+		std::function<double(double x, double y0, double y1)> f,
+		double eps = 1e-6);
+
+	Pwl &operator*=(double d);
+
+	std::string toString() const;
+
+private:
+	static void map2(const Pwl &pwl0, const Pwl &pwl1,
+			 std::function<void(double x, double y0, double y1)> f);
+	void prepend(double x, double y, double eps = 1e-6);
+	int findSpan(double x, int span) const;
+
+	std::vector<Point> points_;
+};
+
+} /* namespace ipa */
+
+} /* namespace libcamera */