Bottom line, with the possible exception of multilayer/page tiffs
(depending on what kind of support Gimp is supposed to have - import
seems good, export not), Gimp png, jpeg, and tiff file formats all
look/work just fine.
Thank you, Elle. I updated the GEGL porting matrix with your findings.
Pngs, tiffs, jpegs:
I did some more testing. I tried opening an assortment of pngs, jpegs,
and tiffs created by a variety of image editing programs (recent
versions of krita, cinepaint, showfoto, an older version of Photoshop,
and test images downloaded from the web), and Gimp opened them all
with
