mapBrightness8to5()

u8 fl::mapBrightness8to5 ( u8 brightness_8bit )

inline

Map 8-bit brightness to 5-bit (0-31)

Parameters

brightness_8bit

Input brightness (0-255)

Returns

5-bit brightness (0-31)

Note

Ensures non-zero input maps to non-zero output (fixes issue #1908)

Uses bit-shift approximation on AVR to avoid expensive division

Definition at line 20 of file encoder_utils.h.

                                                            {
    #if defined(FL_IS_AVR)
    // AVR-specific: Use bit shifts to avoid expensive division
    // Approximation: (value * 31) / 255 ≈ (value * 31) >> 8
    // Add rounding: ((value * 31) + 128) >> 8
    u16 bri5 = ((u16)brightness_8bit * 31 + 128) >> 8;
 
    // Ensure non-zero input doesn't map to zero output
    if (bri5 == 0 && brightness_8bit != 0) {
        bri5 = 1;
    }
 
    return static_cast<u8>(bri5);
    #else
    // Non-AVR: Use accurate division
    u16 bri5 = ((u16)brightness_8bit * 31 + 128) / 255;
 
    // Ensure non-zero input doesn't map to zero output
    if (bri5 == 0 && brightness_8bit != 0) {
        bri5 = 1;
    }
 
    return static_cast<u8>(bri5);
    #endif
}

References FL_NOEXCEPT.

Referenced by encodeAPA102_HD(), and encodeSK9822_HD().

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