EmperorSteele, never mind, I found the files I needed.
Cyrus XIII, most likely something like S-Spline or maybe just simple bilinear interpolation, depends on the time I have. SaI and Eagle etc are only good algorithms for sprites with contrasting colours, not good for general purpose interpolations. Besides, it's not coming anytime soon till I iron out all other bugs first.
And yeah, I already know about the upper left hand corner glitch. It affects nearly all spells / summons. I have yet to find time to fix it.