͏ Thanks for mentioning.
͏ ----
͏ Matters most:
͏ ffmpeg -v debug -hide_banner -nostdin -nostats -i "W020170309545700135684.jpg" -i "W020170309545700291313.jpg" -lavfi "hstack,format=rgb24" -sws_flags gauss+accurate_rnd+print_info -lossless 1 -q 100 -compression_level 6 "gauss-full_chroma_int.webp"
͏ Per the doc "format" doesn't support "flags":
͏ https://ffmpeg.org/ffmpeg-filters.html#format
͏ Hacky workaround required:
͏ ffmpeg -v debug -hide_banner -nostdin -nostats -i "W020170309545700135684.jpg" -i "W020170309545700291313.jpg" -lavfi "sws_flags=gauss+accurate_rnd+print_info; hstack,format=rgb24" -lossless 1 -q 100 -compression_level 6 "gauss-full_chroma_int.webp"
͏ (per [ https://ffmpeg.org/ffmpeg-filters.html#Filtergraph-syntax ])
͏ And there seems to be no solution for "-sws_dither", "-param0", "-param1": which may matter at times.
