For certain TrueType fonts, extracting emojis to PNG files is quite easy. This is because of something called the sbix table contains the emojis as PNG files. Using the fonttools package and Python, it’s almost trivial:
This seems to work great for e.g.
AppleColorEmoji.ttf. The output is a bit
obscure, since you have to look it up via Unicode codepoint, but this is just a proof-of-concept.