pwl.h

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/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * Copyright (C) 2019, Raspberry Pi Ltd
 *
 * Piecewise linear functions interface
 */
#pragma once

#include <algorithm>
#include <functional>
#include <string>
#include <utility>
#include <vector>

#include "libcamera/internal/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);
    Pwl(std::vector<Point> &&points);

    void append(double x, double y, double eps = 1e-6);

    bool empty() const { return points_.empty(); }
    void clear() { points_.clear(); }
    size_t size() const { return points_.size(); }

    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 */