full-screen color playfield (was Re: [stella] Classic people in Next Generation mag)

Subject: full-screen color playfield (was Re: [stella] Classic people in Next Generation mag)
From: Eric Fischer <eric@xxxxxxxxxxxxxxxxxx>
Date: Fri, 17 Apr 1998 16:07:45 -0500 (CDT)
> From: Lee Seitz <lkseitz@xxxxxxxxxxxxxx>

> ObStellaProgramming:  Here's a question for the list.  We've seen that
> the 2600 can handle sampled sounds.  Everyone remember "Stella says,
> 'write a new game'"?  Would it be possible to display a digitally
> stored photograph?  Not necessarily as part of a game, just for the
> sake of doing it.  Like the sound demo.

OK, so doing this in black and white by brute force works decently...
but has anyone come up with a decent algorithm for convering a generic
*color* image into something that can be displayed on the playfield?

What I tried was doing a brute force search of the possible 2600 colors
to find the two best matches to the colors on each scanline (one for
the playfield, one for the background) and then doing a generic
diffusion dither to map the 40 actual pixels to one of those two
colors, figuring that over the course of a few scanlines the colors
that weren't too close to either of the best two would finally get
their turn.  It turns out to work half decently for some images (though
the 40-pixel horizontal resolution makes just about anything turn out
really fuzzy) but the two-color-per-scanline limitation turns out to
mean that anything that actually needs more than two colors fades into
complete gibberish.

After this, I tried alternating colors on different frames, but that
still looked awful, flickered horribly, and took up way too much
memory.  So does anyone have other ideas?  The only other thing I could
think of was to use the two players to add two more colors or more
detail, albeit only to selected vertical stripes, but there doesn't
seem to be enough CPU time to fiddle the playfield and the background
and the players and the colors of all of these on every scanline.


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