Feature suggestion: Tell me which of the 4 compressors gave the best result.
Also, since the point of testing 4 png compressors is to get the smallest size possible, why not use "smallest" as the default setting?
This is a good idea, but I can't technically do this currently. The compressors are run one after another (it's essentially like "pngcrush infile outfile && optipng outfile && advpng outfile && pngout outfile"), so there is no real "best result", it just gets a bit smaller each time.
Also, since the point of testing 4 png compressors is to get the smallest size possible, why not use "smallest" as the default setting?
That's a good point, I've just committed the change :)
Thanks for the suggestions!