gPhoto is a program and library framework that lets users download pictures from their digital cameras. The libgphoto2 library gives you access to hundreds of models of digital cameras on several platforms. GIT repo and Issue tracker lives at https://github.com/gphoto/ these days.
GTK+ comic book viewer.
MComix is a user-friendly, customizable image viewer. It is specifically designed to handle comic books (both Western comics and manga) and supports a variety of container formats (including CBR, CBZ, CB7, CBT, LHA and PDF). MComix is a fork of Comix.
A full featured cross-platform image library
Developer's Image Library (DevIL) is a cross-platform image library utilizing a simple syntax to load, save, convert, manipulate, filter and display a variety of images with ease.
Comix is a user-friendly, customizable image viewer. It is specifically designed to handle comic books, but also serves as a generic viewer. It reads images in ZIP, RAR or tar archives (also gzip or bzip2 compressed) as well as plain image files.