The 
data flow programming environment, developed by
Logical Vision Ltd., has been used to implement all the image
processing algorithms presented in this thesis [3]. WiT
programs are called igraphs. An example igraph is shown in
Figure 1.1. This example low pass filters, then displays
the image stored in the file, ``saturn.wit''.
Figure 1.1: An example WiT igraph.
An igraph consists of a set of operators connected by flows. In Figure 1.1, rdObj, lopass2d, and display are operators. Operators are procedures that operate on the data objects that flow into them. The procedural parameters for each operator are listed below that operator. WiT comes with several libraries that include a rich set of ``standard'' image processing operators. Igraphs can be hierarchical and any igraph can be converted into a hierarchical operator which can then be used by another igraph. Therefore, a hierarchical operator can be thought of as a procedure which encapsulates the functionality of an igraph. Custom libraries, objects, and operators can be added to WiT using the provided definition languages. The definition languages describe the customizations to the WiT environment. Objects and operators are implemented using the C programming language.
WiT igraphs provide an intuitive visual framework for describing algorithms and are therefore used to outline the algorithms developed in this thesis. Custom operators, not included with the standard WiT libraries, are prefixed with ``mri''.