buildRgbSolveMatrixFromQ16()

bool fl::buildRgbSolveMatrixFromQ16	(	const EmitterChromaticitiesQ16 &	profile,
		EmitterSolveMatrixQ16 *	out )

Build the inverse emitter matrix from a Q16 profile, without floats.

The float-free counterpart of buildRgbSolveMatrixQ16, and the second half of P9 item 2: that one converts float chromaticities through xyY_to_XYZ and invert3x3 before quantising, so a target that never wants a float symbol cannot use it.

ci/color_fixed_profile_study.py prices what this costs against the float derivation: worst 0.1085 dE2000 on BT.2020, against A1's 0.5 and the ~0.35 the derivation has once the gamut mapper's 0.15 is counted.

False on the same profiles buildRgbSolveMatrixQ16 refuses – a non-positive or degenerate chromaticity, a non-positive luminance, or a matrix the inverse cannot represent – with one addition the float path has no equivalent of: a y small enough to quantise to zero, which would otherwise be divided by.

Definition at line 265 of file device_solve.cpp.hpp.

                                                                         {
    if (out == nullptr) {
        return false;
    }
    i64 red[3];
    i64 green[3];
    i64 blue[3];
    if (!emitterColumnQ16(profile.xy_r, profile.lum_r, red) ||
        !emitterColumnQ16(profile.xy_g, profile.lum_g, green) ||
        !emitterColumnQ16(profile.xy_b, profile.lum_b, blue)) {
        return false;
    }
 
    // Columns are the emitters' XYZ contributions at full drive, the same
    // arrangement `buildRgbSolveMatrixQ16` builds in float.
    const i32 emitter[3][3] = {
        {static_cast<i32>(red[0]), static_cast<i32>(green[0]),
         static_cast<i32>(blue[0])},
        {static_cast<i32>(red[1]), static_cast<i32>(green[1]),
         static_cast<i32>(blue[1])},
        {static_cast<i32>(red[2]), static_cast<i32>(green[2]),
         static_cast<i32>(blue[2])},
    };
    return invert3x3Q16(emitter, out->m);
}

References FL_NO_EXCEPT, and invert3x3Q16().

Referenced by buildRgbSolveMatrixQ16().

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