Imaging's functionality can be extended by so called extensions. These provide additional file format support, interaction between Imaging and various graphics APIs and libraries (OpenGL, Direct3D, SDL) and other functionality.
Extensions can be divided into two categories. One that is used automatically by Imaging core like image file format extensions. Imaging will register all these extensions on startup.
Second category extensions provide user interface to some extended functions like OpenGL texture creation. These extensions are ordinary Pascal units. If you want to use them simply add these units to your project's uses list and call their functions. Those extensions are currently not accessible using DLL/SO interface.
There is also another extension classification.
Extensions that meet Imaging's crossplatform and/or other requirements are
Source directory (core extensions).
Extensions that do not meet them are located in