Well, how about the plugins and Harry's filters used in XnView? They're written for Win-32, not Win-64, I think, so they may need to be rewritten to be used in 64-bit edition of XnView.
會利用媒體,他就是英雄。
(If one can utilize the media, he is the hero.)
The separate download worked for me, see links posted by XnTriq. Maybe x64 users
should stay away from "full" editions for the moment, and get what they need in
pieces known to be good for x64. Plus the then missing plugins, notably WebP