Support high resolution graphics / artwork upscale

[alula]

The issue is basically as the title suggests - SuperTux right now looks somewhat blurry when the magnification isn't set to 100% and the engine doesn't even have support for HD graphics.

I did some research on that topic and evaluated various automatic solutions for artwork upscaling - so far waifu2x yielded most promising results:

Upscale results (zero manual edits)

Command line used: waifu2x-ncnn-vulkan -i $f -o upscaled/$f -n -1 -s 2

Applied in-game, quickly hacked together (I plan to push a PoC on my fork later):

Obviously, it's not 100% perfect and needs some minor manual edits - notably by fixing the seams, however it's WAY less effort than redrawing the sprites from scratch.
The results seem to mostly depend on quality of source graphics - the tool prefers hand-drawn, non-blurry graphics - any blurriness or mix of hand drawn and pixel perfect lines drastically reduce the quality.

[HybridDog]

I did some research on that topic and evaluated various automatic solutions for artwork upscaling

Which ones have you tried? Does it give better results than RealSR and Real-ESRGAN?

[alula]

I think that Real-ESRGAN is the best bet. Needs some extra tools to deal with seams and transparent edges and manual editing for perfect results.