Ok, to update, I worked on this pixel art scaling, so HQnX not good results, I found the scalenX family MMPX which is really interesting. But the best with some fixes is the omniScale (which is even better than rotsprite sometimes while rotsprite is not a real time algo).
Maybe I can add an other fix on the lines but should be quite hard if the line is more complexe.
So I will add this on the next release too.
I was going to open another thread to ask for pixel art scaling options, but I had a "deja vu", so I searched here, and yeah, as usual, you made what I wanted even before I knew it XD
I have been trying the omniscale option to scale up pixel art and it's amazing! :D 
Why are you not telling people that PixelOver have this feature on the main page? Seriously, this is great! :D
Having said that, would it be possible in the future to add also some other scaling algorithms? Not all of them act the same and some ones could be better for certain specific art than others. Maybe you could use even Rotsprite (even if it's not a real time algorithm, you could put a warning maybe?).
Just in case it's useful, some examples and interesting info here (you'd probably know them already though):
https://en.wikipedia.org/wiki/Pixel-art_scaling_algorithms
https://www.datagenetics.com/blog/december32013/index.html
Edit: I have just seen it, you have it announced on the main page with "Transformation/Deformation. Stay pixel-perfect when rescale, rotate or deform an object.". Nice ^^
2 years ago(+1)
I didn't find another really better than omniscale, do you want some particularly ? Rotsprite I can try but yes I need to apply it async may be problematic with animation and export, I need to check
Not any one in particular, I'd just like to have some of them to be able to test them (apart from the emulators I don't know any other software that let you choose many pixel art scaling algorithms, so I cannot really experiment with them).
This's a very low priority request though. I'm already superhappy with having omniscale and nearest neighbour in PixelOver :)