ImageMagick 7
darktable is an open source photography workflow application
Library to encode and decode images in WebP format
A fast image processing library with low memory needs
Swiss army knife of image processing
Scanning probe microscopy data visualisation and analysis
Lynkeos is an astronomical webcam image processing software for OS X.
ProStack - a platform for image processing and analysis
Image processing library in C/C++
Astronomical object/structure detection from 1D and 2D data sets.
Tools to access streams in PDF-files at the object level.
Collection GIMP plugins by zvezdochiot
Easy converting pgm and ppm to (MASK+FG+BG)-djvu.
Improved JPEG encoder
Libraries and command line tools for medical image processing.
Graphic Live Mixer
Digital image processing programs for Windows and Linux systems.
Some image processing tools
A small C library for building user interfaces with C, XML and CSS.
Tools to train Image Operators automatically from a set of samples.
Advanced image processing toolbox for Scilab on Unix/Linux/Mac OS