Class alpha8

src/fl/math/alpha.h:42–78

Unsigned 8-bit alpha / brightness — UNORM8. Represents values in [0.0, 1.0] inclusive. Interpretation: raw / 255 raw 0 = 0.0 raw 128 = 128/255 ~ 0.502 raw 255 = 255/255 = 1.0 FastLED's scale8() uses the (scale+1)>>8 approximation for efficient UNORM scaling: scale8(x, 255) == x (exact identity). Implicit conversion to/from unsigned char preserves full backward compatibility with code that tre

/// Implicit conversion to/from unsigned char preserves full backward
/// compatibility with code that treats this as a plain u8.
struct alpha8 {
    unsigned char value;

    constexpr alpha8() FL_NOEXCEPT : value(0) {}

    // Accept any non-bool integer type (signed or unsigned, any width).
    template <typename IntT, alpha_detail::enable_if_integer_t<IntT> = 0>
    constexpr alpha8(IntT v) FL_NOEXCEPT : value(static_cast<unsigned char>(v)) {}  // NOLINT — implicit by design

    explicit constexpr alpha8(float f) FL_NOEXCEPT : value(_clamp(f)) {}
    explicit constexpr alpha8(double f) FL_NOEXCEPT : value(_clamp(static_cast<float>(f))) {}
    constexpr operator unsigned char() const FL_NOEXCEPT { return value; }

    constexpr unsigned char raw() const FL_NOEXCEPT { return value; }
    constexpr float to_float() const FL_NOEXCEPT { return value / 255.0f; }

    static constexpr alpha8 from_float(float f) FL_NOEXCEPT {
        return alpha8(static_cast<unsigned char>(_clamp(f)));
    }

    alpha8& operator+=(unsigned char rhs) FL_NOEXCEPT { value += rhs; return *this; }
    alpha8& operator-=(unsigned char rhs) FL_NOEXCEPT { value -= rhs; return *this; }
    alpha8& operator*=(unsigned char rhs) FL_NOEXCEPT { value *= rhs; return *this; }
    alpha8& operator/=(unsigned char rhs) FL_NOEXCEPT { value /= rhs; return *this; }
    alpha8& operator>>=(int rhs) FL_NOEXCEPT { value >>= rhs; return *this; }
    alpha8& operator<<=(int rhs) FL_NOEXCEPT { value <<= rhs; return *this; }
    alpha8& operator++() FL_NOEXCEPT { ++value; return *this; }
    alpha8 operator++(int) FL_NOEXCEPT { alpha8 t = *this; ++value; return t; }
    alpha8& operator--() FL_NOEXCEPT { --value; return *this; }
    alpha8 operator--(int) FL_NOEXCEPT { alpha8 t = *this; --value; return t; }

  private:
    static constexpr unsigned char _clamp(float f) FL_NOEXCEPT {
        return static_cast<unsigned char>(
            f <= 0.0f ? 0 : (f >= 1.0f ? 255 : static_cast<unsigned char>(f * 255.0f + 0.5f)));
    }
};

/// Unsigned 16-bit alpha / brightness — UNORM16.
/// Represents values in [0.0, 1.0] inclusive.