Probably you mean opening *.png
files, mime type x-apple-ios-png
with gnome commander.
The answer is there: http://gcmd.github.io/doc.html. Create three files in ~/.local/share/applications
directory:
mimeapps.list
[Default Applications]
image/x-apple-ios-png=eog-usercreated.desktop
eog-usercreated.desktop
[Desktop Entry]
Name=eog
MimeType=image/x-apple-ios-png;
Exec='/usr/bin/eog'
Type=Application
Terminal=false
NoDisplay=true
mimeinfo.cache
[MIME Cache]
image/x-apple-ios-png=eog-usercreated.desktop
It works under Ubuntu 14.04.1, Gnome Commander 1.2.8.17
[shared-mime-info]
(askubuntu.com/q/486404/58950), to no avail.