Webpgoy from umi here: What does /g/ think of lossless Webp? To clarify I'm not the site owner, I'm just another image codec autist.
>Relative to lossless JXL filesize, how close in compression does a given lossless image codec get?
That's what I'm trying to answer here. A dozen common type 1920x1080 PNG images were used.
4chan still doesn't support lossless Webp but umi does, so I'll post the oxiPNG files here and lossless Webp ones in umi.
https://umigalaxy.com/explore/general/785-lossless-webp
JXL KB = 100% and BMP KB = 0%. Lossless JXL/Webp/AVIF/oxiPNG/QOI tested. Anything above 100% means JXL was defeated.
cjxl in.png out.jxl -d 0.0 -e 10 --brotli_effort=11
cwebp -lossless -m 6 -q 100 in.png -o out.webp
avifenc -l -s 0 --cicp 1/13/16 in.png out.avif
oxipng -o 6 in.png
qoi "...\in.png" "...\out.qoi"