Export graphic suitable for thermal printer

[rawles]

Raquel has requested an additional export option which produces a graphic optimised for output on a mini thermal ('receipt') printer, for example https://www.adafruit.com/product/597 - this could be used at events to allow people to take their work home.

The output would minimise massive blocks of black as is often seen in teletext frames, and maybe convert the other colours to some appropriate level of grey.

[ZXGuesser]

Why minimising black particularly? Just because the contrast isn't very high, or some technical consideration?

[rawles]

I think because it looks better. It was a request from Raquel, who has produced things like this.