[adzm]

Do you mean lossless? PNGs are not lossy. A large photo with alpha channel in a lossless png could easily be 20x the size of a lossy webp

[archerx]

No I meant lossy. This is the library I use; https://pngquant.org/

[thunderfork]

Pre-processing does not a codec make (this is why .gif is considered lossless even though you lose all that 24-bit colour goodness)

[archerx]

Fair enough but it gets the job done well none the less.

[Semaphor]

PNG of course can be lossy. They aren’t great at it, but depending on the image can be good enough.