Re: Max colour output
Posted: Thu Sep 27, 2018 8:29 pm
Yeah, sorry, what I said was all jargon.93143 wrote:I understood some of those words... I'm still very userspace on this topic, but I'm sure it would make more sense if I read up on those resources.lidnariq wrote:On the other hand, coming back to this after another 3 years I can see trivially how to do subpalette generation more easily (namely, don't use ppmquant, instead use pnmcolormap on the colorspace-reduced reference, and use pnmremap from the highcolor original, with floyd-steinberg dithering)
subpalette = the 16-color palette I'm using on each scanline
tools from the "netpbm" software suite:
ppmquant = tools that generate a colormap, remaps colors, and handles dithering all in one program.
pnmcolormap = a tool that just generates that colormap
pnmremap = a tool that just remaps colors and handles dithering
pnmquant= a convenience wrapper that runs both pnmcolormap and pnmremap. Doesn't handle pipes.
pertinently, my previous attempt:
1- Started with the original image
2- Converted it to X bpp (X=9 for TG16, 15 for SNES)
3- divided this depth-reduced version into single-scanline high bits
4- converted each depth-reduced scanline on its own into the final result (without dithering)
5- combined all of those slices.
This time, I instead
4a- only used the depth-reduced scanline for its resulting palette.
4b- I go back to the original image, extract the corresponding full-depth single scanline
4c- and reconvert that slice of the full-depth scanline using the palette generated in 4a (with dithering)
Using Floyd-Steinberg dithering (or any other error propagating type) is really limited by only being able to propagate error within its own scanline, as is happening here. Positional dither might be an easier way to get better results.
But I can't see any way to apply these techniques to something where the palettes across scanlines have to have some correlation, which makes CypherSignal's idea so interesting.