In this tutorial, we will see how to crop a picture with Gwenview on Ubuntu. Gwenview is a free image viewer for KDE and it can be installed under Ubuntu. If you still haven't installed Gwenview on Ubuntu (11.04/10.10/10.04), launch the terminal and issue this command:
sudo apt-get install gwenview
To crop a picture with Gwenview, right-click on any picture you have and select Open With > Gwenview.
In the right vertical toolbar, click Crop.
A resizable window will appear in the same dimensions as your picture. Using your mouse cursor, resize and move this window until you get it fit with the desired part on your picture you want to crop, then click Crop.
You have now cropped the picture, press Ctrl + S to save it. That's it!