There are a myriad of PNG (and in general DEFLATE) optimizers and pingo hosts its own benchmark [1]. I believe ECT [2] is the only tool comparable to pingo in terms of compression ratio and speed. But pingo still lacks a license statement and it's even unclear whether you can use this for any purpose at all, probably because it is still "experimental", so if you don't like that you can try ECT instead.
> One thing I didn't check is that you might pay that in decoding time, I've never seen anybody talking about that though.
PNG and in general DEFLATE-based formats are mostly free from this concern because they are comparably simple. The maximum "overhead" you can intentionally trigger is a very large LZ77 window and a very deep prefix code tree; the former is however capped to 32 KB in DEFLATE, and the latter will mostly result in an inferior compression (a longer prefix code means a larger file).
Yes. I have no idea why ECT gets left off of lists so often, because it's almost always within 1% of the best tools on size, and at least several times faster than them on speed.
As far as I can tell, pingo isn't cross platform or open source, in addition to the issue you mention with the license statement, which makes it extremely limiting for e.g. automated processing of images on a server. I think ECT is absolutely a reasonable choice for most use cases.
I didn't know about ECT even after searching for a while. Maybe it's lacking in visibility? I'll give it a try.
As for pingo, I can run it without issues with wine. I would personally prefer an open source tool though, so if ECT is really around 1% of pingo and not too much slower, I would prefer it.
> One thing I didn't check is that you might pay that in decoding time, I've never seen anybody talking about that though.
PNG and in general DEFLATE-based formats are mostly free from this concern because they are comparably simple. The maximum "overhead" you can intentionally trigger is a very large LZ77 window and a very deep prefix code tree; the former is however capped to 32 KB in DEFLATE, and the latter will mostly result in an inferior compression (a longer prefix code means a larger file).
[1] https://css-ig.net/benchmark/png-lossless
[2] https://github.com/fhanau/Efficient-Compression-Tool