The AVIF image format is quite nice.
* comte.png 83KiB → comte.avif 31KiB
* factotum.png 84KiB → factotum.avif 38KiB
* procureur.png 74KiB → procureur.avif 31KiB
A real page like https://mnt.io/series/reactive-programming-in-rust/observability/ decreases from 336KiB to 285KiB (-51KiB).
Not negligible at all.
Thanks @GIMP for native support :-].