Swiss army knife of image processing
itom - an Open Source Measurement, Automation and Evaluation Software
Emgu CV is a cross platform .Net wrapper for OpenCV
Advanced image processing toolbox for Scilab on Unix/Linux/Mac OS
Graphical Interface for Medical Image Analysis and Simulation
A Multi-functional GUI-based Program for Image Processing and Analysis
TurboSphere is an easy to learn and powerful JS based game engine.
A Library for Interactive Modelling and Visualisation
Computer vision and image processing library for Qt.
Siril is an astronomical image processing software for Linux.