This is the code I used on "hand flip" 10,000 CryptoPunks into V3 CryptoPhunks to enable the V3 Phunk launch and 50 eth MAPS charity donation.
The code takes as its input the original 24x24 CryptoPunk images and outputs 1200x1200 flipped Phunks with the sea green background color.
The flipping logic is written using a Ruby library called `MiniMagick`, which is a wrapper around the famous `ImageMagick` command line tool. It's pretty straightforward to convert this to an ImageMagick command if you don't use Ruby.
Notably, in ImageMagic, the "flip" command is called "flop." Paradox?
I used the Ruby `Parallel` library to process as many images simultaneously as I have CPU cores (I think eight). This is crucial: even with max parallelism slowing my computer to a crawl, this still took over 10 mins. Without Parallelization it would have taken over an hour.
Code license: MIT. Use it for free! But: you have to buy this NFT first! KIDDING!