[josephg]

Yes. I wanted to do that, but I couldn't find a png library on npm that supports encoding 4 bit paletted pngs. Fixing that was on my todo list from day 1.

Although now that I think about it, I could probably get close by using an 8bit greyscale image and then apply the palette in the client. That would probably halve the image size.

[Drdrdrq]

Cool project! Optipng does many other optimisations but could be taxing on CPU. It should be very easy to put it in the stack for test though.