ZX81: Printing in Colour using the Chroma Interface

ZX80, ZX 81, ZX Spectrum, TS2068 and other clones
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RobertK
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Posts: 215
Joined: Mon Feb 26, 2018 12:58 pm

ZX81: Printing in Colour using the Chroma Interface

Post by RobertK »

The Chroma Interface is a little special: you can't freely display colour, but you can define background and foreground colours for each character of the ZX81 character set, and this still can be very effective. The ZX81 emulator "EightyOne" can emulate the Chroma Interface, you can activate it in the Options menu in the "Hardware" settings.

I am working on a little game that I could easily colourize using the "Chroma Program Enhancement Creator", but I would prefer to add native Chroma support. However, I am a little lost. I had a look at z8048.c which natively supports Chroma, but I don't entirely unterstand what's happening there.

Can any of you please write a hello world program that
- inverts all characters to get a white on black screen, and
- e.g. displays each "h" letter in a specific background and foreground colour, and each "l" letter in another
?

Here is the Chroma documentation (archived versions because Paul is currently having some web hosting problems):

https://web.archive.org/web/20190909071 ... erface.htm
https://web.archive.org/web/20160321174 ... iption.txt
https://web.archive.org/web/20160828065 ... mBASIC.htm
stefano
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Posts: 1628
Joined: Mon Jul 16, 2007 7:39 pm

Post by stefano »

The Chroma interface does even more, it's able to produce a colour screen in graphics mode.
Please have a look at the wall.c demo, it deals with screen attributes directly for different targets including the MSX.
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