Graphics remapping techniques?

[ccovell]

Okay, so everybody knows that the PCE's 9-bit colour space is pretty limited.  Especially when remapping photographs or high-colour art, you get banding, flat colours, or have to resort to a high amount of dithering.

Does anyone know of a paint program that can remap 24-bit -> 9-bit (or any other colour space in RGB (non-indexed)) and apply dithering at the same time?

One technique which I've toyed around with in the meantime:

(The images at the bottom have been posterized again into the PCE's 8-level colour space.)

Each combination of posterization levels gives a different dithering type, to high dither, dither in dark colours only, bright colours only, narrow dithering bands, etc.  There's no perfect balance that I've found, so one has to select the best-looking type for each picture:


Any other good ideas?

[Arkhan]

NeoPaint!

Has tons of dithering modes also.   Sierra is my favorite.

NeoPaint is my favorite Paint program, especially for PCX related things.

[ccovell]

With all due respect, NeoPaint is a step in the wrong direction.  Simplified options, 16- 256- colour indexed modes only: it's for kids.

What I asked about above is not about programs for dithering 24-bit down to 16 indexed colours.  There are plenty of those.  I'm looking for ways to remap 24-bit RGB down to, for example, 15-bit RGB, or 9-bit RGB non-indexed, and perhaps apply some picture voodoo during the conversion process.

[Arkhan]

Oh.  I read your post too fast because I was doing something else at the same time.

I'm not really an art person.  16 colors dithered is about all I can manage, so I have no idea.  Maybe sunteam_paul knows, hes smrt.

[sunteam_paul]

I dunno, I kind of went from Dpaint to Photoshop and am only just getting started on all this mysterious PCE palette stuff.

[Bonknuts]

Chris, that's a fantastic method you've got there. I take it that the posterization there is straight, right? How about a weighted conversion to each posterized level? I've toyed with that idea in the past (a non linear rounding scale). It'd be interesting to try that in conjunction with the method you described. Either way, nice job Have you tried out Orion's Magictreme?

[ParanoiaDragon]

Anyone tried asking Nod or Keranu?  Or what about Frag?  I saw him on IRC last nite, maybe he'd know?

[ccovell]

I take it that the posterization there is straight, right? How about a weighted conversion to each posterized level?

Bonknuts, that's it!!!  Regular posterization won't work, so a pair of colour biasing curves has to be created for each image.

Here's a set of curve maps for Photoshop that'll do regular 8-level and 15-level posterization... but also the two 8-level posterizations that'll dither into 15 levels:
http://www.chrismcovell.com/data/PCE_Remapping_Curves.zip

Here's a demonstration:

[esteban]

Can you use apply this technique on the same reference photo (of the SuperCD + CoreGrafx combo) for comparison purposes?

Thanks in advance

[ccovell]

Okay, here are the old methods next to the new (15-level dither) method:

[nodtveidt]

You would have a hell of a time getting that onto the real hardware though. The colors are correct but you'd have a murderous time trying to reduce 8x8 blocks to only sixteen 15+1 color palettes. 402 uniques in the entire image, and I couldn't get a 256x224 selection at any lower than around 260 uniques. Even with sprite mixing, you'd be at this for hours... and I know; I've been working with Black Tiger's highly colorful images, which are already designed for the PCE palette limitations, and it can take up to 3 hours to get a single image reduced enough to fit into 16 palettes.

Of course, if you can get this technique to work for actual pics you would use in a real game, it might be a different story. It really depends on the source, and whether or not you want to do color reduction blending (that is to say, combining similar colors without noticeable detail loss).

[ccovell]

Naah, this is just a reference pic.  And if I wanted to get that much colour in, I'd overlap sprites and BG.

[Bonknuts]

Chris, how do I use those files you posted?

[esteban]

Chris, thanks for posting the reference pics. Pretty damn nice, I say.

If only the cover art for the Ultra Box catalogs used some of these techniques

[ccovell]

Chris, how do I use those files you posted?

You'll need Adobe Photoshop.  Get your image, select Adjust->"Curves", click "load", and change the file extension in the load dialogue to *.amp.