http://waifu2x.udp.jp/
^ THIS IS SOME GOOD STUFF (just pretend it's called something else)
drawn at 100%!
and then upscaled x2 in waifu
THEN AGAIN
but if i do it in sai..
notcool
WORKS ON TRANSPARENT LINEARTS TOO
and for colored images. it's said that it doesn't work quite as well with anything soft shaded or
painterly BUT IMO, still works
pretty damn great. borderline flawless on hard, smooth linearts. I used the marker tool which has some opacity which explains the slight fading in the resized example images!
I HOPE YOU ENJOY