 Digital topology

Digital topology deals with properties and features of two-dimensional (2D) or three-dimensional (3D) digital images
that correspond to topological properties (e.g., connectedness) or topological features (e.g., boundaries) of objects.Concepts and results of digital topology are used to specify and justify important (low-level) image analysis algorithms, 
including algorithms for thinning, border or surface tracing, counting of components or tunnels, or region-filling.