Gwenview, the image viewer for KDE, is the Cadillac of the bunch. As with the other viewers, you can use it to preview images (thumbnails) and their filenames on the left side of the screen, and see full-sized images in a larger window on the right.
The program has a host of batch file processing options. For instance, it can convert a bunch of .jpeg files that were taken using a digital camera to .png for Web site use. Gwenview can import and export the following formats: JPEG, PNG, PPM, BMP, and TGA. You can import TIFF, but can't export it.
Some of the other batch processing functions let you add borders to your images and normalize, solarize, or edge-detect your scenes. Edge detection can create line drawings from your scene elements.
Gwenview uses external graphics editors to change pictures. You can select a picture, then right-click on the External Tools menu item to pick your editor, or you can add your favorite editor under the Settings tab.
Slide shows are a strong point of Gwenview. You'll find the option under the Plug-in tab. Click Tools -> Slide shows for a setup screen. You'll see a multitude of transition effects. For instance, the Cube transition puts each image on a cube and spins it around to display it. Fading between slides is very smooth. The transition time is selectable in milliseconds and has a lower limit of 1 second. Since Gwenview supports looping, it would work well in a signage application, too.
Gwenview - click to enlarge
Gwenview has an HTML album creator, which you can find under the Plug-in tab. Click Export -> HTML Export to assemble albums from selected images or an entire directory. You can also select the number of images per row, the look of your borders, or the background colors. Click through the Selection, Look, Album, and Thumbnail screens to review options.
Gwenview also has a calendar creator. With it, you select your font style and 12 images. Press Next, and poof, the application creates a calendar using your images.
For a full featured thumbnail viewer package with a lot of options, Gwenview is my choice.
gThumb is a fast little viewer originally for the GNOME desktop. gThumb version 2.3.3-9 came bundled in the SUSE 9.2 Linux, and I used it with KDE. It displays a list of filenames on the left and shows each thumbnail image on the right. If you double-click on an image, gThumb replaces the thumbnails with a scrollable view of the selected image. It also offers various zoom, rotate, and single image format conversions.
gThumb - click to enlarge
If you fill in meta information for each image, such as comments and categories, gThumb has a search feature you can use to locate an image. Naturally, you can search by date or file name as well.
You can create a Web image album by selecting images and filling in a theme and HTML file name under the Tools -> Create Web Album menus. gThumb creates an index file you can upload (along with the images) to your server. The HTML file displays each image, the ones before and after, comments, and navigational arrows. The themes are limited but attractive.
For a good balance of speed and ease of use, you won't go wrong with gThumb.
GQview is simple and basic, and probably the fastest viewer on this list. When you select a thumbnail, the image appears immediately in the right window. Displayed images are of very high quality. All the usual functions are there, including image zooming, rotating, and flipping, but GQview lacks any format conversion functions.
GQview has an editable list of editors, too. You can use GQview to quickly move through your images, then click on your favorite industrial strength graphics editor to make changes. My default SUSE 9.2 configuration offered a selection of the Gimp, xv, and xpaint. This capability sure would have saved me some time on a recent book project.
GQview - click to enlarge
You can create slide shows and start them with a right click and Start Slide show selection. The default transition time is one second, but you can alter that under the Preferences tab. GQview can either go alphabetically down the filename list, or you can use Ctrl and left mouse clicks to select the images you want to include.
GQview is a good viewer for use on older hardware, when you hate to sit around waiting for things to load.
Finally, xzgv is just a simple viewer with a featherweight (653KB) footprint. If you just want to view images quickly, this is the program for you.
Qiv is a command-line viewer application that you can run in an Xterm window. It has the same zoom, rotate, and image manipulation capabilities of the GUI viewers, with all the rich capabilities of the command line.
For example, if you wanted to quickly produce a slide show of your .png images, gather them in a directory and in an Xterm type:
qiv -s -d 5 *.png
The images will appear, one by one, with a five-second delay between slides. Pressing Escape ends the slide show.
You can specify options such as contrast, maximum picture size, brightness, and image centering when starting the program. See the help menu or man pages for a lengthy list of options.
Qiv also functions in interactive mode, using the keyboard and mouse. Basic keyboard commands are intuitive, such as the plus/equal sign to zoom in and the minus sign to zoom out. The lower-case h flips an image horizontally, while the lower-case v flips an image vertically. Mastering functions beyond the basics requires a good memory or a cheat sheet.
This program is great for fast setup and display of your slides. Since it runs from the command line, you don't have to mess around with on-screen buttons or mouse clicking.
XV - click to enlarge
XV is really only a pseudo thumbnail viewer. It has been around for years and works well for viewing images. You have to load files from a file list tree, without a preview, and the images show up in a separate window. Once an image file is loaded, you can bring up each image by clicking on its filename. So, it sort of has thumbnail viewing capabilities.
XV has no slide show mode, but it can convert images to a different format; all you need do is change the extension and save. It works with all the major formats -- GIF, JPEG, PNG, and TIFF. Click on the Save button, then click and hold the Format button to see a complete list of export formats.
Even though XV is a little outdated in the user interface department, it is a solid viewer that you can use to quickly flip through a list of pictures.
As with everything else in the open source world, thumbnail viewers give users a variety of capabilities and features. There is sure to be one that meets your needs.
Rob Reilly is a consultant, writer, and commentator who advises clients on business and technology projects. His articles regularly appear in various Linux and business media.