gamma.hpp

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//
// Created by spak on 9/23/21.
//
 
#ifndef NEO_GAMMA_H
#define NEO_GAMMA_H
 
#include <array>
#include <map>
#include <memory>
#include <mutex>
 
namespace neo {
    struct gamma_table {
        using lut_table_t = std::array<std::uint8_t, std::numeric_limits<std::uint8_t>::max() + 1>;
        lut_table_t lut = {};
 
        gamma_table() = default;
        inline explicit gamma_table(lut_table_t lut_);
 
        [[nodiscard]] inline std::uint8_t operator[](std::uint8_t v) const;
 
        [[nodiscard]] std::uint8_t reverse_lookup(std::uint8_t v) const;
 
        [[nodiscard]] static gamma_table build(float gamma);
    };
 
    class gamma_table_cache {
        std::map<signed, std::unique_ptr<gamma_table>> _gamma_to_table;
        float _gamma_multiplier;
        std::mutex _lookup_mutex;
 
        [[nodiscard]] signed gamma_to_key(float gamma) const;
 
    public:
        static constexpr unsigned default_precision = 2;
 
        explicit gamma_table_cache(unsigned precision = default_precision);
 
        [[nodiscard]] gamma_table const &operator[](float gamma);
    };
 
    [[nodiscard]] gamma_table const &get_cached_gamma_table(float gamma);
 
}// namespace neo
 
namespace neo {
    gamma_table::gamma_table(lut_table_t lut_) : lut{lut_} {}
 
    std::uint8_t gamma_table::operator[](std::uint8_t v) const {
        return lut[v];
    }
}// namespace neo
 
#endif//NEO_GAMMA_H