And just for kicks, since Calibre is also using ImageMagick, we can do it right
. [While I happen to like IM, note that it's not the only way, KCC happens to be doing it right w/ PIL
]
Slightly more involved patch, which remaps to the eInk palette & dithers, and does the letterboxing for fullscreen covers (provided I didn't bork my maths, looks okay on initial testing). It also happens to be dramatically faster than using quantize, so that's neat.
(This affects Calibre's magick Python/C module, so you'd need to build Calibre yourself to test this).