Vic 20 dithering support added (preliminary)

robin-raymond commented 11 months ago

The Vic 20 has some unique attributes that are similar but different than the Commodore 64. The Vic 20 doesn't have a true graphics mode but instead relies on character re-imaging and color choices to make a pseudo bitmap. Combined with the Vic 20's flexible screen sizes, this makes an interesting target.

Some key differences added:

In multi mode, the Vic 20 has the choice of 4 color options just like the C64, except three of the choices are the background, border, and auxiliary color. These are global colors, and then each block gets the choice of its own foreground color.
In hires mode, the choice is the background or a foreground color for the block
In multi-mode the palette is fully available for the background, and aux color but a palette subset is used for the aux color and the foreground color.
In hires mode, the palette is restricted for the background and the foreground color.

Code changes (some refactoring):

The global color selection is improved, because the choice of global colors is so critical for the vic, the background, aux, and border colors are selected by pixels, whereas commodore 64 only uses the background (at times), the logic now first uses histogram usage to pick the top N colors based on usage if the color is useable by the image's pixels. The remaining colors that are needed to have compatible colors are based on the intensity and are selected for palette compatibility to the image rather than overall usage.
the palette options got a lot more complex in the settings so those got split out into their own dithering settings with appropriate defaults that would mean the rest of the settings don't need to specify anything and they will still work
the pixel color choices now respect the palette subset that can happen in the case of the Vic 20
added VIC 20 palette colors (there are some differences between systems but this is true of the C64 as well)
added export bin routines for the Vic 20 which are likely to produce nothing much of useful value given they aren't tested against working code
misc typos and a few inconsistencies in the code (code could use a good auto-format tool as I find the editors liking to do it the way they think the code should be not how the code is)

robin-raymond commented 11 months ago

sehugg commented 11 months ago

VIC-20! It's getting serious now! :) This ought to be cool.

BTW, it might take me a little while to merge because I'm refactoring into proper TypeScript modules, so some files will be moved around. But it should be a little more manageable, and no major API changes.

robin-raymond commented 11 months ago

Oh yes! This is an up-and-coming platform, I just know it! In all seriousness, the Vic 20 needs some love. I couldn't let this platform be neglected with such a useful tool given I knew most of the Commodore code would be able to also handle the Vic 20 with small tweaks. Then I discovered Vic 20's 10-color choice graphics ;-). See images below for a sneak peak!

Understood about the merge. Since I am not a typescript expert, I'll leave that up to you because I honestly don't know what is "proper".

robin-raymond commented 11 months ago

BTW, the display on the UI that says "WWW x HHH, N colors, WxH" probably needs an asterisk when it comes to the Vic-20! While the Vic technically has 16 colors, the actual palette gets restricted to 8 for some of the colors (depending on context) despite the wider palette being present. It's a bit a bit weird but you can tell the Commodore engineers were trying to squeeze every bit of power out of that machine despite its cost reduce form.

sehugg commented 11 months ago

Wow that looks great! I agree the VIC-20 needs a little love, I hope i can get the emulator working one day, at least with cartridges.

I pushed the Typescript refactoring, and I'm pretty sure it broke the PR, sorry. Don't want to break your momentum. The files are reorganized, but you ought to be able to cut-and-paste your changes and add a few exports and imports here and there. I did find a way to bundle the .asm files as plain text files, so that's nice. Let me know if you need help with the new structure.

robin-raymond commented 11 months ago

Wonderful news! I'll sync the code up and fix the PR in the coming day(s).

robin-raymond commented 11 months ago

Replacement PR is up. You may reject this one.

sehugg / dithertron

Vic 20 dithering support added (preliminary) #19