Nomacs is an open-source image viewer, working on Linux and Mac OS X, under the GNU General Public Licence v3. Nomacs is lightweight and fast and has support for all the popular image formats, like JPEG, PNG, GIF, ICO, BMP and RAW.
The latest version available is Nomacs 3.12.0, coming with changes.
Installation instructions:
Up to date packages are available via some third party PPA, so installing the software on Ubuntu systems is easy. Add the PPA to your system, update the local repository index and install the nomacs package:
$ sudo add-apt-repository ppa:dhor/myway
$ sudo apt-get update
$ sudo apt-get install nomacs
Optional, to remove nomacs, do:
$ sudo apt-get remove nomacs
The installation instructions work for Ubuntu 18.10 Cosmic Cuttlefish, Ubuntu 18.04 Bionic Beaver, Linux Mint, Elementary OS and other Ubuntu derivative systems.