five_bit_hd_solve16() [2/2]

void fl::detail::five_bit_hd_solve16	(	u16	r16,
		u16	g16,
		u16	b16,
		u8	min_field,
		CRGB *	out,
		u8 *	out_field )

Definition at line 184 of file five_bit_hd_gamma.cpp.hpp.

                                                     {
    // Target light per channel, in code x field units with eight fraction
    // bits: a drive of 65535 is 255 x 31. The legacy solve's field rule is
    // not monotonic at 16-bit resolution -- a one-step rise can move it to a
    // field whose rounding lands lower -- so this uses its own: the smallest
    // field f with T < 255.5 f, and codes rounded at that field. Within a
    // field, rounding is monotonic; across a transition the new field's light
    // is at least T - (f + 1) / 2 > 255 f, which is at least the old field's
    // maximum. So emitted light never falls as a drive rises.
    if (min_field < 1) {
        min_field = 1;
    }
    if (min_field > 31) {
        min_field = 31;
    }
    const u16 drives[3] = {r16, g16, b16};
    u32 target[3];
    u32 brightest = 0;
    for (int i = 0; i < 3; ++i) {
        target[i] = static_cast<u32>(
            (static_cast<u64>(drives[i]) * 7905u * 256u) / 65535u);  // 7905 = 255 x 31; u64 throughout (AVR int is 16 bits)
        if (target[i] > brightest) {
            brightest = target[i];
        }
    }
    // 255.5 in eight fraction bits is 65408.
    u32 field = brightest / 65408u + 1u;
    if (field < min_field) {
        field = min_field;
    }
    if (field > 31u) {
        field = 31u;
    }
    const u32 unit = field * 256u;
    for (int i = 0; i < 3; ++i) {
        const u32 code = (target[i] + unit / 2u) / unit;
        out->raw[i] = static_cast<u8>(code > 255u ? 255u : code);
    }
    *out_field = static_cast<u8>(field);
}

References fl::FL_NO_EXCEPT.