The voxel data class is the central repository of all data relating to the 3D MRI’s, etc., and their segmentation. It contains the greylevel, segmented and color-label data, which it can read and write out as necessary. It also deals with requests for all aspects of this data such as dimensions, a slice, etc. This class acts as a passive server to all other classes, and will only respond to requests from other classes. It is the final repository of data for an iris process. All changes to it are final within a process, and can only be undone if the requesting module has some undo information, or if data is reloaded from a disk file.