Agar provides a base GUI framework and a standard set of widgets from which graphical applications can be built which run natively under X11, Windows, MacOS, SDL and others. It takes advantage of texture and GPU acceleration wherever available. Agar can also attach to an existing framebuffer, SDL or OpenGL context and operate as a self-contained window-manager.
It includes a standard library of general-purpose widgets, and is also designed to be extended externally. New widgets can be...
Please see laidout.org for current code and download location.
Laidout is desktop publishing and imposition software for Linux, particularly for multipage, cut and folded booklets, with page sizes that don't even have to be rectangular. Bug reports welcome!
A powerful C++ class library for image manipulation
ImageStone is a powerful C++ class library for image manipulation. Its features include load, save, display, transformation, and nearly 100 special image effects. It can be used cross platform (includes Windows, Linux, Mac), and especially under windows it can be used as a DIB wrapper class.
lib2geom (2Geom in private life) is a library developed for inkscape to provide a robust computational geometry framework. It is not a rendering library, instead concentrating on high level algorithms such as computing arc length.
QtOPENCASCADE is a framework for integrating the OpenCascade Solids Modelling library with the Qt4 toolkit to enable the development of multi-platform CAD and CAE applications.