[Gimp-user] invert not working

[remadepreacher <forums gimpusers com>]

New to Gimp. I have 2.8.22. I have two projects. 1. I simply want to invert a
photo. I was given it by a book designer for my book cover. I had no problem
cropping an edge for the spine in Photos and now want to invert it to match the
front cover. I tried selecting all and then 3 different ways to invert. None
have any effect, except to add "remove invert" to edit. I exported the  photo,
just to be sure — not inverted. Next, I tried adding a layer, then invert — no
effect.
2. I wanted to try Liquid rescale to extend a background. As I'm using OS X,
Wikidots says it should be already in my layer menu — it's not.

Closing gimp, opening and trying again for either — no effect.

-- 
remadepreacher (via www.gimpusers.com/forums)