Gwenview is by far the most popular image viewer for KDE, and it comes with all the features a well-thought image viewing application should have: it provides a file browser, previews, resizeable thumbnails, and a wealth of plug-ins for basic image manipulation. The sidebar will display image information, together with shortcuts to several useful file operations, like left/right rotation, resize or red eye reduction. You can also insert ratings for your images, up to five stars (handled the same way Amarok 2.0.2 handles ratings for audio files).
Gwenview 2.2.2 - file browser with thumbnail previews
Gwenview is very fast and the port for KDE 4 has a redesigned interface, including the configuration window which is now cleaner (however it lacks several options from the KDE 3, but they will probably be implemented in the versions to come). It supports various image formats, including the popular PNG, JPG, BMP, TGA or XPM formats.
Simply put, Gwenview should be the number one image viewer choice for KDE3 and KDE4 users.
sudo apt-get install gwenview
Eye of GNOME
Well, Eye of GNOME is a simple image viewer for the GNOME desktop environment, but although it has a basic interface it supports many formats. EoG thrives for simplicity, and it comes with a basic, easy-to-use interface, it allows images to be displayed as a slideshow, and it offers basic image manipulation functions like rotate image, zoom in/out, or set as desktop background (works in GNOME).
sudo apt-get install eog
Eye of GNOME 2.26.0
QIV is the acronym for Quick Image Viewer, a very basic image viewer for the X Window System. Although the interface is the most basic there could be, QIV features image zoom, scale, slideshow, rotate image, and even gamma, contrast or brightness correction. However, you will need to know the keyboard shortcuts in order to use those features, which you can find by using the man qiv command.
sudo apt-get install qiv
QIV 2.1 - a viewer with a minimalist interface
Using KDE3 libraries, KuickShow is yet another image viewer, lighter and offering fewer features than Gwenview, but nevertheless, good enough for viewing images in a fast manner. It offers basic image manipulation functions like changing the brightness, contrast or gamma, rotate images, zoom, or save image as a different format.
KuickShow 0.8.13 - a good alternative to Gwenview on KDE 3.5.x
KuickShow is highly configurable and includes a file browser as well.
sudo apt-get install kuickshow
KuickShow - minimalist interface
GQview is a nice, GTK+ image viewer with a clean and intuitive interface with lots of features, including file browser or image manipulation tools. GQview is definitely a very good alternative to the default viewer in GNOME, Eye of GNOME.
sudo apt-get install gqview
This viewer is the default image viewer in LXDE (Lightweight X11 Desktop Environment) and it offers a minimal interface without menus but a toolbar located at the bottom of the application which includes the main buttons one needs to operate with it. GPicView is worth a look at, no matter what desktop environment you are using.
sudo apt-get install gpicview
GImageView, another GTK-based viewer offering pretty much the same features as the last two viewers. It includes a file manager and it opens images in a new, separate window.
You can run it as gimv in the Run dialogue or from a terminal.
sudo apt-get install gimageview
Also built in GTK, gThumb provides a clean interface and supports many image formats. gThumb is one of the most popular viewers in GNOME, being easy to use and configure.
sudo apt-get install gthumb
This article is part of a series of reviews I'm putting up. Here are the links to the other reviews of Linux applications I've recently published:
14 Most Popular Text Editors for Linux
10 File Managers for Linux
12 Popular Audio Players for Linux - An Overview
5 Best Applications to Rip and Transcode DVDs in Linux