[Gimp-user] Gimp 2.10 - Color to Alpha is greyed out

[MCBastos <forums gimpusers com>]

Further testing (and a hint from another forum) revealed the root of the
problem: the images didn't have an alpha channel. If I add an alpha channel
(can't find a convenient one-click option for that, so I'm making do with adding
a transparent layer and merging it to the main image), it works fine.

Still can't figure out why the portable version does not require this extra
step. Must be something in the settings, which probably have different defaults
in the portable... I'll have to dig further.

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