Optimizing pik against ssimulacra

[khavishbhundoo]

maxerror,filesize,butteraugli,ssimulacra
1.0,117241,0.999972,0.02952750

Its clear that pik is optimizing against butteraugli but it would be nice to see it optimized for ssimulacra as well

[jyrkialakuijala]

Ssimulacra is mostly a L2 norm based distance. Before guiding compression with it, one would need to make it local, for example maximum based, otherwise an optimization could compensate an error on left side of image by making the right side more accurate.

https://encode.ru/threads/2814-Psychovisual-analysis-on-modern-lossy-image-codecs?p=54071&viewfull=1#post54071 demonstrates the issue.