unit_color_utility.hpp

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/*
 * SPDX-FileCopyrightText: 2025 M5Stack Technology CO LTD
 *
 * SPDX-License-Identifier: MIT
 */
#ifndef M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_HPP
#define M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_HPP
 
#include "../unit/unit_TCS3472x_data.hpp"
#include <algorithm>
#include <cmath>
#include <tuple>
#include <cassert>
#include <type_traits>
 
namespace m5 {
namespace unit {
namespace tcs3472x {
 
// GA = 1.08 when the sensor is placed behind clear glass (pass it via dgf)
constexpr float GA{1.0f};           
constexpr float DF{310.f};          
constexpr float DGF{GA * DF};       
constexpr float R_Coef{0.136f};     
constexpr float G_Coef{1.0f};       
constexpr float B_Coef{-0.444f};    
constexpr float CT_Coef{3810.f};    
constexpr float CT_Offset{1391.f};  
 
constexpr float AT_NORMAL_FACTOR{2.4f};                 
constexpr float AT_NORMAL_MIN{AT_NORMAL_FACTOR};        
constexpr float AT_NORMAL_MAX{256 * AT_NORMAL_FACTOR};  
constexpr float WT_NORMAL_FACTOR{AT_NORMAL_FACTOR};     
constexpr float WT_NORMAL_MIN{WT_NORMAL_FACTOR};        
constexpr float WT_NORMAL_MAX{256 * WT_NORMAL_FACTOR};  
constexpr float WT_LONG_FACTOR{2.4f * 12.f};            
constexpr float WT_LONG_MIN{WT_LONG_FACTOR};            
constexpr float WT_LONG_MAX{256 * WT_LONG_FACTOR};      
 
struct Calibration {
    Calibration(const uint16_t br, const uint16_t wr, const uint16_t bg, const uint16_t wg, const uint16_t bb,
                const uint16_t wb)
        : blackR{br}, whiteR{wr}, blackG{bg}, whiteG{wg}, blackB{bb}, whiteB{wb}
    {
        assert(wr > br && "White must be greater than black");
        assert(wg > bg && "White must be greater than black");
        assert(wb > bb && "White must be greater than black");
    }
 
    uint16_t blackR{};  
    uint16_t whiteR{};  
    uint16_t blackG{};  
    uint16_t whiteG{};  
    uint16_t blackB{};  
    uint16_t whiteB{};  
 
    inline uint8_t R8(const Data& d) const
    {
        return linear(d.RnoIR16(), blackR, whiteR);
    }
    inline uint8_t G8(const Data& d) const
    {
        return linear(d.GnoIR16(), blackG, whiteG);
    }
    inline uint8_t B8(const Data& d) const
    {
        return linear(d.BnoIR16(), blackB, whiteB);
    }
 
    inline static uint8_t linear(const uint16_t raw, const uint16_t low, const uint16_t high)
    {
        if (raw <= low) {
            return 0U;
        }
        if (raw >= high) {
            return 255U;
        }
        return static_cast<uint8_t>(
            std::round((static_cast<float>(raw) - static_cast<float>(low)) / (static_cast<float>(high - low)) * 255.f));
    }
};
 
inline float atime_to_ms(const uint8_t a)
{
    return 2.4f * (256 - a);
}
 
inline float wtime_to_ms(const uint8_t w, const bool wlong)
{
    return atime_to_ms(w) * (wlong ? 12 : 1);
}
 
inline uint8_t ms_to_atime(const float ms)
{
    int tmp = 256 - std::round(ms / 2.4f);
    return static_cast<uint8_t>(std::max(std::min(tmp, 0xFF), 0x00));
}
 
std::tuple<uint8_t, bool> ms_to_wtime(const float ms);
 
float calculateLux(const uint16_t rawR, const uint16_t rawG, const uint16_t rawB, const uint16_t rawC,
                   const float atime_ms, const Gain gc, const float dgf = DGF, const float coefR = R_Coef,
                   const float coefG = G_Coef, const float coefB = B_Coef);
 
float calculateColorTemperature(const uint16_t rawR, const uint16_t rawG, const uint16_t rawB, const uint16_t rawC,
                                const float coefCT = CT_Coef, const float offsetCT = CT_Offset);
 
uint16_t calculateSaturation(const uint8_t atime);
 
inline uint16_t calculateSaturation(const float atime_ms)
{
    return calculateSaturation(ms_to_atime(atime_ms));
}
 
template <typename T, typename std::enable_if<std::is_integral<T>::value && !std::is_same<T, uint8_t>::value,
                                              std::nullptr_t>::type = nullptr>
inline uint16_t calculateSaturation(const T atime)
{
    return calculateSaturation(static_cast<uint8_t>(atime));
}
 
float calculateCRATIO(const uint16_t rawR, const uint16_t rawG, const uint16_t rawB, const uint16_t rawC);
 
float calculateCPL(const float atime_ms, const Gain gc, const float dgf = DGF);
 
inline float calculateMaxLux(const float atime_ms, const Gain gc, const float dgf = DGF)
{
    return 65535.0f / (3.0f * calculateCPL(atime_ms, gc, dgf));
}
 
template <typename T, T... Ints>
struct integer_sequence {
    typedef T value_type;
    static constexpr std::size_t size()
    {
        return sizeof...(Ints);
    }
};
 
// Porting C++14 features to C++11
// clang-format off
template <size_t... Ints>
using index_sequence = integer_sequence<size_t, Ints...>;
 
template <typename T, size_t N, T... Is>
struct make_integer_sequence : make_integer_sequence<T, N - 1, N - 1, Is...> {};
 
template <typename T, T... Is>
struct make_integer_sequence<T, 0, Is...> : integer_sequence<T, Is...> {};
 
template <size_t N>
using make_index_sequence = make_integer_sequence<size_t, N>;
// clang-format on
 
// constexpr version of std::pow is GCC4.6.1 or higher
#if __GNUC__ > 4 || (__GNUC__ == 4 && (__GNUC_MINOR__ > 6 || (__GNUC_MINOR__ == 6 && __GNUC_PATCHLEVEL__ > 0)))
#define M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_CAN_CONSTEXPR_MAKE_GAMMA_TABLE
#define M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_CONSTEXPR constexpr
#else
#define M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_CONSTEXPR
#endif
 
inline M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_CONSTEXPR uint8_t calculate_gamma(const float x, const float gamma)
{
    return static_cast<uint8_t>(std::pow(x, gamma) * 255 + 0.5f);  // Rounded
}
 
template <size_t... Indices>
M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_CONSTEXPR std::array<uint8_t, sizeof...(Indices)> make_gamma_table_impl(
    const float gamma, index_sequence<Indices...>)
{
    return {calculate_gamma(static_cast<float>(Indices) / 255.0f, gamma)...};
}
 
template <size_t Size = 256>
M5_UNIT_COLOR_UTILITY_UNIT_COLOR_UTILITY_CONSTEXPR std::array<uint8_t, Size> make_gamma_table(const float gamma = 2.2f)
{
    return make_gamma_table_impl(gamma, make_index_sequence<Size>{});
}
 
}  // namespace tcs3472x
}  // namespace unit
}  // namespace m5
#endif