flat-level RMS error (8-bit levels) through the painterly pass; no dither: 0.2887
dither                               pixel ratio 1   pixel ratio 2   pixel ratio 3
white noise                                 0.0896          0.0896          0.0896
Bayer 16x16                                 0.0700          0.3552          0.0700
blue noise (64x64 void-and-cluster)          0.0702          0.0907          0.0905
blue noise, one tile per coset              0.0702          0.0702          0.0702
interleaved gradient noise                  0.0687          0.0674          0.0665
R2                                          0.0726          0.0718          0.0703
best lattice for this pass                  0.0580          0.0583          0.0584