Alright so since we don't know when sharty will enable jpeg xl on 4chan I started looking for alternatives and it surprised me that one was hiding right in the libjxl folder: jpegli, which practically speaking is the biggest threat to webp right now because it can make backwards compatible JPG images that have lower file sizes which mozjpeg couldn't do. As far as I understand JPG images encoded from say the 90s required around 2-3 BPP for high quality while those encoded with jpegli now only require 1-2 BPP so the file size reductions are pretty huge even for personal use.
Anyway for those interested I made a windows batch script that not only lets you select what quality level you want but also gives you a ssimulacra2 score and if the score isn't good enough, you can retry again without launching the script again. There's a lot of disagreement on what this should be but I've personally found diminishing returns around 85 so that's what I'm going to stick with.
@echo off
:loop
echo:
set /p q="Por favor quality: "
FOR /R %%G IN (*.png) DO cjpegli "%%~G" "%%~dpnG.jpg" ^
-q %q% --chroma_subsampling=444 -p 0 --fixed_code &&^
echo: && echo SSIMU2 = &&^
ssimulacra2 "%%~G" "%%~dpnG.jpg" && echo:
set /p retry="Test again? YES or NO?: "
if /i "%retry%"=="YES" goto loop
if /i "%retry%"=="yes" goto loop
if /i "%retry%"=="Yes" goto loop
Another really interesting thing I almost forgot to point out is one of the big reasons why most people hate webp is the fact that it only supports 4:2:0 chroma sub-sampling which IMHO is like a huge step backwards compared to JPG. Literally 75% of all color information is permanently destroyed when you use 4:2:0.