GIMP is the GNU Image Manipulation Program. It is a freely distributed piece of software suitable for such tasks as photo retouching, image composition and image authoring. 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, a image format converter, etc.
Fotoxx navigates an image collection using a thumbnail browser to choose images to view or edit. Edit functions include brightness, contrast, color, gamma, white balance, tone mapping, red eyes, sharpen, blur, noise suppression, smart erase, trim (crop), resize, rotate, add text, bend/warp, many art effects, HDR, HDF, stack, and panorama. Edit functions use movable curves and sliders. Feedback is live using the whole image. RAW files can be edited and saved with deep color. Areas or objects can be selected using freehand draw, follow edge, and tone matching. Selections can be edited in place with adjustable blending. They can also be cut and pasted into other images. Any metadata can be edited, reported, and searched (filenames, tags, dates, geotags, comments, captions, ratings, etc.). Collections (arbitrary subsets) can be defined and viewed. Batch functions are available for rename, resize/export, RAW conversion, and more.
GraphicsMagick is a robust collection of tools and libraries which support reading, writing, and manipulating an image in over 90 major formats including popular formats like DPX, DICOM, BMP, GIF, JPEG, JPEG-2000, PDF, PNG, PNM, SVG, and TIFF. A high-quality 2D renderer is included, which provides a subset of SVG capabilities. C, C++, Perl, Tcl, and Ruby are supported. Originally based on ImageMagick, GraphicsMagick focuses on performance, minimizing bugs, and providing stable APIs and ABIs. It runs on all modern variants of Unix, Windows, and Mac OS X.
SIP provides image processing, pattern recognition, and computer vision routines for SciLab, a Matlab-like matrix-oriented programming environment. SIP is able to read/write images in almost 90 major formats, including JPEG, PNG, BMP, GIF, FITS, and TIFF. It includes routines for filtering, segmentation, edge detection, morphology, curvature, fractal dimension, distance transforms, multiscale skeletons, and more.
Tux Paint is a simple and entertaining drawing program geared towards young children. It has a simple interface, sound effects, and a cartoon character (Tux, the Linux penguin). Along with drawing brush strokes, lines and shapes, you can also enter text and place "rubber stamp" (or "sticker") images on the picture. Tux Paint is extensible, and could be useful in an educational environment (such as a grammar, elementary, or grade school). It's portable across numerous platforms, and runs well even on slower systems like the Pentium 133MHz.
Evolvotron is an interactive "generative art" application to evolve images/textures/patterns through an iterative process of random mutation and user-selection driven evolution. If you like lava lamps, and never got tired of the Mandelbrot set, this could be the software for you. It's implemented using Qt, and is multithreaded.
mtPaint is a simple GTK+1/2 painting program designed for creating icons and pixel-based artwork. It can edit indexed palette or 24 bit RGB images and offers basic painting and palette manipulation tools. Its main file format is PNG, although it can also handle JPEG, GIF, TIFF, BMP, TGA, XPM, and XBM files.
Barcode Studio is designed to quickly create high-quality barcode images. It is commonly used for pre-press requirements, postal bar-coding, desktop publishing applications, mobile tagging, print shops, and general barcode purposes. It supports all linear barcodes (like Code39, 2of5, EAN, UPC, Code39, Code128, and EAN/UCC128), 2D barcodes (like PDF417, QR-Code, Aztec Code, DataMatrix ECC200, and MaxiCode), GS1 DataBar, and HIBC codes. Barcode data can be entered manually or imported from external data sources. Serial numbers are created automatically on demand. It has a built-in quality preview. Single as well as batch barcode creation is supported via the command line or the graphical user interface. Barcodes can be printed directly, copied to the clipboard, generated as image files (BMP, GIF, JPG, TIFF, or PNG) or exported as vector graphics (EPS, EMF, WMF , PDF, or PostScript). The created barcodes are useable immediately: Just insert the barcode graphics into your artwork, database, form, or any document.
XPaint is an easy-to-use image editor which supports many standard and less standard paint procedures that demanding non-professional users would expect. It includes several advanced features like image processing algorithms, programmable C scripts, simultaneous editing of multiple images, and supports a wide variety of image formats.
GTKRawGallery is a workflow-oriented photo retouching program with the necessary tools to quickly process camera raw images. It brings together Dcraw, Imagemagick, and Exiftool. Important features include an image browser and manager for popular formats, a full-featured Dcraw GUI for fine-tuned raw image pre-processing, image modification tools for 16-bit/channel post-processing, batch conversion with single workflow applicable, a batch processor to speed up the workflow, fast tagging, an advanced metadata editor with EXIF, IPTC, and XMP write support, color management, and print support, Facebook, Flickr, and Picasa Web Albums publishers, and a Dropbox uploader.