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.
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.
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.
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.
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.
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.
Grafx2 is a bitmap paint program that allows you to draw in more than 60 video resolutions (from 320x200 to 1024x768, including most of the standard Amiga resolutions: 320x256, 320x512, 640x256, 640x512, and more, provided your video card knows how to handle them). Its layout is not very different from the famous Deluxe Paint or Brilliance, so it will be quite easy to handle it if you know at least one of these programs.
Raster3D is a set of powerful tools for generating high quality raster images of proteins or other molecules. The core program renders spheres, triangles, cylinders, and quadric surfaces with specular highlighting, Phong shading, and shadowing. It uses an efficient software Z-buffer algorithm that is independent of any graphics hardware.