NGI is a generic image processing and image analysis library.
Let us dissect the important terms of this definition.
Image processing is the global name for programming techniques that deal with images on input and recreate other images on output.
Image analysis goes a step further in that it tries to extract meaning from an image. Usually the output of an image analysis algorithm is not another image, but some different data, such as the number of objects in an image.
Library is the term for a piece of code that's available in the form of a toolbox. Software pieces to be assembled by a programmer to fulfill a task. The NGI library is a C++ library available in source code.
Generic is the opposite of specific.
Read more at http://code.google.com/p/ngi/