No quality for png (oxipng)?

I am testing this library to replace imagemin, however I cannot find a quality setting for oxipng and level does not seem to effect the image size. In the issues I found that oxipng replaced optipng which may have had a quality setting?

What would be the way to actually compress a PNG?

I did some testing with quant’s numColors and this works:

   const preprocessOptions = {
                quant: {
                    // numColors: 128
                }
            };
            await image.preprocess(preprocessOptions);

but I am not sure if this is the prefered method to make PNG significantly smaller and wether other png libraries do the same thing (as in lowering the amount of colors) when they apply a lower quality.

I can imagine that an image with tons of colors would need a different numColors setting to still look okay, so it would be great if there is a quality setting that takes this into account.

[jakearchibald]

Here’s a version from Squoosh that’s only 80kb:

[jakearchibald]

Yep, this looks like palette reduction to me, which Squoosh can already do.