 A recursive definition of the digital k-manifold was proposed intuitively by Chen and Zhang in 1993.Many applications were found in image processing and computer vision.A basic (early) result in digital topology says that 2D binary images require the alternative use of 4- or 8-adjacency or "pixel connectivity" (for "object" or "non-object"
pixels) to ensure the basic topological duality of separation and connectedness.