Hey guys! Holy crap, I just discovered this filter and the latest scalefx-aa presets that @guest.r posted in August. This is nothing short of spectacular!!
@hunterk, will these make it to the repos?
I used to be excited about xBRZ und xBR-mlv4-multipass (still am), but your collective work here blows them out of the water. I’d seen “scalefx” before and thought, hey somebody should anti-alias that, not realizing you guys were already on it
I just spent 2 days reading through this thread and even though a lot of it is Klingon to me, I have some observations and I hope perhaps I can be of some value with them.
a) aa or rAA?
First, imho the scalefx-aa filter is superior to the scalefxx+rAA+aa one. It seems sharper to me:
I wasn’t quite sure if you guys originally considered / now consider the rAA version superior? If so, why? I didn’t quite glean that from the technicalities along this thread.
b) Faded colours
I noticed that in some cases, colours on scalefx-aa look less saturated than on “nearest” (i.e., original) or 6xBRZ. Check out the bright cyan pixels on the waterfall in Blackthorne or the top left square on the top left flag in Colonization:
I’m wondering if there’s a way to restore the lost saturation or luminance? I retouch photos a lot and I find that in Gimp or Darktable, the “local contrast” (aka “Unsharp Mask”) tools are able to do that. They’re intended to perceptually increase sharpness by increasing contrast between adjacent areas. I’m not sure… Just a thought?
c) Struggles with DOSBox’s “vgaonly” mode
Since the filters only work on unscaled images, they struggle with games like Commander Keen or Prehistorik 2, which require the “vga” mode in DOSBox to work (otherwise they crash).
That mode scales 320x200 up to 640x400 (which is by design), so then you end up with this when using the scalefx-aa filter:
With @hunterk’s help, I was able to work around this using the xbr-mlv4-multipass filter by adding an extra pass at the beginning that downscales the resolution to half before any of the other filter passes run. More info here:
When I do the same with scalefx-aa-fast (here’s the exact preset I concocted), this happens:
I’m wondering if you guys can think of a fix/workaround? I’ll be happy to implement it myself and then provide my preset here, assuming it’s not beyond my understanding.
d) Curves where there should be angles?
I’m pretty sure that’s a “no”, but I noticed that sometimes, the image suffers a bit when the scalefx-aa filter creates curves where there should be angles. For example, the t in “Nintendo”:
There’s probably no way to make these filters smart enough to work around this?
Anyway, so much from me for now.