This can be done much faster. The problem is memory/disk bound. Decoding the PNGs should be most of the work if written properly. Edit: Yes, this is more reas

This can be done much faster. The problem is memory/disk bound. Decoding the PNGs should be most of the work if written properly. Edit: Yes, this is more reasonable: https://news.ycombinator.com/item?id=25405595 https://news.ycombinator.com/item?id=25405595