Subject: Re: [stella] Optimized color reduction approaches From: "Andrew Davie" <atari2600@xxxxxxxxxxxxx> Date: Wed, 12 Feb 2003 20:07:32 +1100 |
> I think this is how the COLRVIEW technique as used with GR8 on the > Atari8-bit. Is that what you are trying to emulate? It just like a 1-bit > version of COLRVIEW. It may be similar, though I am not specifically trying to emulate this. I've been interested for a long time in ways of improving the colour capability of '2600 bitmap screens - as far back as my PUSH demo in '98 or '99 I was experimenting with time-based interlacing to give more colours onscreen. As with many things in technology, sometime it's simply the right TIME for something to happen - and several people may independantly be working on the same thing without knowing about each others' efforts. In this case, I was attempting colour imagery with 6-sprite routines before I became aware of the "high resolution bitmap" thread on AtariAge which asked if such a thing were possible. I contributed to that thread for a while, but am rather annoyed at the moment with how it degenerated to a personal thing. It's highly likely that I got some of my ideas from that thread - but bear in mind that I was already thinking of techniques and discussing the same with others. My efforts did not flow as a direct attempt to copy the techniques mentioned in those discussions - I just did what I thought might work. In particular, the separation to separate colour planes and the stippled 2-colour reduction of each is probably something anyone tackling the problem would eventually decide to do. Likewise, the multiplexing/interlacing of the RGB lines isn't a particularly tricky technique - just a few lines of code - and something just about anyone would eventually try. I don't claim to have invented the technique - but nor do I admit to copying it. Probably among the many bits of information I picked up during my thinking about the problem lead to my solution/technique. It's rather pointless saying who invented it, or who deserves credit. Look, for example, at the recent "interlacing" triumph. Many of us had a significant hand in the development of that technique. Only one person ACTUALLY produced the first demo showing the technique. > Another thing you might want to emulate is GED on the Atari8. GED involves And with my efforts to date, my interest in this technique is now completed. I have *absolutely no* interest in the sort of GED techniques - and I'll happily leave THAT challenge to Thomas :) Cheers A ----- Original Message ----- From: "Glenn Saunders" <mos6507@xxxxxxxxxxx> To: <stella@xxxxxxxxxxx> Sent: Wednesday, February 12, 2003 6:17 PM Subject: [stella] Optimized color reduction approaches > At 05:06 PM 2/12/2003 +1100, you wrote: > > > Looks great. I really like to weird look of the very wide pixels. The > > > interlacing looks nice and really reduces the flicker. It just kinda > >shimmers. > > > >It's not actually interlaced - at least, it's not an interlaced TV frame. > > I knew something didn't look quite right about it ;) > > >It's kind of double-interlaced in that each individual scanline > >alternatively displays RGB, GBR, BRG... and the lines are out-of-synch with > >each other, so consecutive lines display RGBRGBRGB etc.... That is, while > >one line is displaying the red values for that line, the next line is > >displaying it's green values, and the one after that displaying blue values. > > > I think this is how the COLRVIEW technique as used with GR8 on the > Atari8-bit. Is that what you are trying to emulate? It just like a 1-bit > version of COLRVIEW. > > Another thing you might want to emulate is GED on the Atari8. GED involves > blocking out zones of color on the horizontal and doing color register > changes in mid screen almost like HAM on the Amiga, but obviously you can > only change registers a few times. On the Atari you might only be able to > change it once or twice per line. But this tends to work well for cartoon > style artwork where you might have one character on one end that is mostly > blue, let's say, and the other character on the right being mostly > red. They could both use the same playfield color register if you changed > it in mid screen over black. > > The other thing you should do is come up with a routine that will optimize > the RGB triad. Like let's say the top part of the screen was generally > darker than the rest. Instead of relying on dithering alone (over black > which is rather flickery to begin with) you could reduce the luminance of > the red green and blue frames. And if the top of the screen is, let's say, > a sky, you could optimize the RGB triad to be 3 shades of blue instead of R > G and B. And as the sky gets generally lighter or darker, you can adjust > the 3 shades of blue to approximate this and try to minimize the dithering. > > This approach wouldn't work well unless the image naturally had zones where > each zone strip had a somewhat dominant, monochromatic color scheme. I'd > really like to see a landscape like a beach scene or something using this > method, or a photo of a real sunset rather than the usual Activision one ;) > > > > > > > -------------------------------------------------------------------------- -------------------- > Archives (includes files) at http://www.biglist.com/lists/stella/archives/ > Unsub & more at http://www.biglist.com/lists/stella/ > > > ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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