KDE4 users know Gwenview the default image viewer for KDE, but may not know that Gwenview is one of the best image viewers ever existed. It is fast, quick, modern, shiny, particularly in full-screen mode, and has basic photo editing functions.
Gwenview does not try to replace your favorite image editor, so it only features the most simple image manipulations: rotation and mirroring, resizing, cropping and exporting images to on-line albums.

Gwenview is a pretty straight forward program to use. In this post I'll try to review the main features of Gwenview.
As image viewer, Gwenview has three modes to achieve this goal: View mode, Browse mode, and Full Screen mode.
View mode is the default mode when you open an image. As shown in next screenshot, the left sidebar has three tabs:Meta information, Image Operations, and Folders tabs. Meta information tab is where you can add your comments, edit the tags, and rate the image.

view mode

 Image Operations gives you basic tools like: Rotate, Mirror, Flip, Resize, Crop, and Red Eye Reduction.

cropping

Also you can open any photo with another application like GIMP, showFoto

Open with

 The second sidebar is thumbnail bar which gives you a fast way to preview all photos.  The default configuration for thumbnail bar in OpenSUSE 11.2 is horizontal and one row. You can change them from Settings > configure Gwenview then Image View panel as shown in the next photo.

Image View settings

Second mode is Browse mode where you can easily navigate through your files and folders. The preview window shows thumbnails of the images in the current folder, as well as subfolders.
Browse mode gives you a wide view to all your photos that in one folder, It is particularly for photographs who want to get a glimpse of what they got.

Browse Mode

The Full Screen Mode shows a slideshow of your images. I love Gwenview because of this mode. It is fast and handy.

Full Screen Mode

You can change the Slideshow settings by clicking on Configure Full Screen Mode button. It gives you simple options like changing the size of thumbnails and the interval's time and type.

Full Screen Mode settings

Gwenview also comes with plugin support, but you'll have to install the kipi-plugins package in order to be able to use them. Kipi-plugins give Gwenview powerful tools like: fantastic Advanced Slideshow, Calender creator and Batch processing tools include border images, convert images, rename images and Image Effects.
By kipi-plugins, you can export and import your photos to a wide range of famous sites like Flickr, 23, picasa, and Facebook. 
If you have not used Gwenview before, why not give it a try. You will love it like me.