ON THE COMPUTATION OF THE DIGITAL CONVEX HULL AND CIRCULAR HULL OF A DIGITAL REGION

✍ Scribed by B.B. CHAUDHURI; A. ROSENFELD

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 250 KB
• Volume: 31
• Category: Article
• ISSN: 0031-3203
• DOI: 10.1016/s0031-3203(98)00065-x

✦ Synopsis

The problems of defining convexity and circularity of a digital region are considered. A new definition of digital convexity, called DL-(digital line) convexity, is proposed. A region is DL-convex if, for any two pixels belonging to it, there exists a digital straight line between them all of whose pixels belong to the region. DL-convexity is shown to be stronger that two other definitions, T-(triangle) convexity and L-(line) convexity. A digital region is T-convex if it is DL-convex, but the converse is not generally true. This is because a DL-convex region must be connected, but T-and L-convex regions can be disconnected. An algorithm to compute the DL-convex hull of a digital region is described. A related problem, the computation of the circular hull and its application to testing the circularity of a digital region, is also considered, and an algorithm is given that is computationally cheaper than a previous algorithm for testing circularity.