I said “-reverse” instead of “-negate” to ImageMagick, so I got an image with the wrong polarity. I interrupted the printer and the thing to the right is the result.
I thought it was mildly interesting that the interrupted edge of the print doesn’t just stop, but kinda drops off. It’s supposed to be 100% black, so I guess this means that my Epson R3000 is printing every bit many, many times when printing “best quality”.
I mean, the printer takes forever, but the result is immaculate.