computeBandShift()

void fl::gfx::detail::computeBandShift ( fl::i32 band, fl::u8 & shift_out, fl::u16 & inv_out )

inline

Precompute right-shift and reciprocal multiplier for AA division.

Converts 32-bit AA division: (diff * 255u) / band (~60 cycles on AVR) into a multiply-by-reciprocal: ((diff >> shift) * inv) >> 8 (~14 cycles on AVR) where inv = round(255 * 256 / scaled).

Definition at line 211 of file primitives.h.

                                                                                       {
    fl::u8 sh = 0;
    fl::u32 tmp = static_cast<fl::u32>(band);
    while (tmp > 255u) { tmp >>= 1; ++sh; }
    shift_out = sh;
    // Reciprocal: (255 * 256 + scaled/2) / scaled — rounds to nearest
    fl::u8 scaled = static_cast<fl::u8>(tmp);
    inv_out = static_cast<fl::u16>((65280u + (scaled >> 1)) / scaled);
}

References computeBandShift(), and fl::FL_NO_EXCEPT.

Referenced by computeBandShift(), drawDiscCore(), drawRingCore(), and drawStrokeLineCore().

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