ImLib3D is a C++ library and visualization system for 3D (volumetric) image processing. It contains most basic image processing algorithms, as well as some more sophisticated ones. Its images are STL-compliant templated containers. It inculdes a viewer that features multiplanar views, interactive image processing, animations, vector field views, and 3D (OpenGL) multiplanar. Its main application is medical image processing.
Moron (Method for Object Recognition of Obscure Nature) is a tool to classify given images based on their content. Technically, it combines feature extraction and machine learning. The classes recognized depend on the version. A typical Moron version tries at least to separate drawn content from photographs (pron) and thus could be adapted as a spam filter for cartoon newsgroups.
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.
Engauge Digitizer is digitizing software that converts an image showing a graph or map into numbers. The image file can come from a scanner, digital camera, or screenshot. The numbers can be read on the screen, and written or copied to a spreadsheet. Highlights for beginners include an intuitive interface and extensive context-sensitive documentation. Highlights for experts include compensation for image distortion, cartesian and polar coordinates, linear and logarithmic coordinates, automatic scanning, graphical previews, and browser help.
Kognition is an omnifont OCR software for KDE. It is the result of two diploma theses about omnifont optical character recognition which are included as documentation (in German). Due to the fact that each step of the OCR process can be visualized you can get a quick idea of how OCR works and where the problems lie. However the program may be of minor/no use for end users in its current state.