So here are my quality judgements. I'm leaving nip2vsqbs and standard Lanczos4 out of these judgements because nip2vsqbs is way too soft and Lanczos4 has way too many ringing artifacts.
Code:
black&white: NNEDI3 > ICBI > PR > EWA LanczosSharp > nonRingingLanczos4 > EWA Robidoux > LBB > LBB-Nohalo > Imagiris
parking: NNEDI3 > Imagiris = ICBI > nonRingingLanczos4 > PR > LBB-Nohalo > LBB > EWA LanczosSharp > EWA Robidoux
clown: NNEDI3 > Imagiris > ICBI > EWA LanczosSharp > nonRingingLanczos4 > PR > LBB-Nohalo > LBB > EWA Robidoux
lighthouse: NNEDI3 > ICBI > Imagiris > EWA LanczosSharp > nonRingingLanczos4 > EWA Robidoux > PR > LBB-Nohalo = LBB
castle: NNEDI3 > Imagiris > nonRingingLanczos4 > EWA LanczosSharp > PR > LBB = LBB-Nohalo > EWA Robidoux > ICBI
biglighthouse: NNEDI3 > Imagiris > ICBI > PR > EWA LanczosSharp > nonRingingLanczos4 > LBB-Nohalo > EWA Robidoux > LBB
Here comes my opinion about those scaling algorithms one by one, sorted for quality:
(1)
NNEDI3: clear winner for me. Not as sharp as Imagiris, but always artifact free, always aliasing free, always halo free, always smooth and pretty, big congrats to tritical
(2) Imagiris: best in sharpness, but too many artifacts to win, probably not a good choice for video, due to artifacts
(3) ICBI: somewhat comparable to NNEDI3 in looks, but a clear step down, also shows some minor artifacting sometimes
(4) EWA LanczosSharp + nonRingingLanczos4: EWA LanczosSharp has noticeably lower aliasing levels than nonRingingLanczos4, but has more halos and is a bit softer
(5) PR: weird algorithm, produces sometimes quite nice results, sometimes rather bad results, sometimes weird artifacts, no good choice for video, due to artifacts
(6) LBB-Nohalo: Too much aliasing for my taste. But on the positive side no halos (surprise!)
(7) LBB: In many cases almost identical to LBB-Nohalo. Sometimes a tiny bit worse.
(8) EWA Robidoux: Too much aliasing and softer than LBB(-Nohalo).
Of course that's just my personal opinion. Anyone else willing to do a detailed judgement?