GIMP (GNU Image Manipulation Program) is a freely distributed piece of software suitable for such tasks as photo retouching, image composition, and image authoring. It is a powerful piece of software with capabilities not found in any other free software product. It can be used as a simple paint program, an expert-quality photo-retouching program, an online batch-processing system, a mass production image renderer, or an image-format converter. GIMP is modular, expandable, and extensible. It is designed to be augmented with plug-ins and extensions to do just about anything. The advanced scripting interface allows everything from the simplest task to the most complex image-manipulation procedures to be easily scripted.
The file format support ranges from the common likes of JPEG (JFIF), GIF, PNG, TIFF to special use formats such as the multi-resolution and multi-color-depth Windows icon files. The architecture allows to extend GIMP’s format capabilities with a plug-in. You can find some rare format support in the GIMP plugin registry.
Thanks to the transparent virtual file system, it is possible to load and save files to from remote locations using protocols such as FTP, HTTP or even SMB (MS Windows shares) and SFTP/SSH.
To save disk space, any format can be saved with an archive extension such as ZIP, GZ or BZ2 and GIMP will transparently compress the file without you needing to do any extra steps.