Shape processing and analysis using the calypter
Éric Pirard · Journal of Microscopy · 1994
Summary After presenting some elementary criteria that should be respected by any automatic shape analysis technique, this paper focuses on the importance of the binary image encoding method. Most image analysers simply use a raster image to represent a binary object. If, occasionally, a vectorial description is available, it is merely chosen for its performances in data compression. Data compression and shape analysis have different goals and usual methods cannot satisfy both. The calypter is a new descriptor vectorizing the shape as a set of maximal inscribed discs. It is the most efficient means of accomplishing Euclidean mathematical morphology transformations and allows for further developments in binary shape processing. A simple adaptive contour filtering technique is presented. The calypter offers local and global perception of shape characteristics. It permits complete automation of the morphometric roundness charts used in many laboratories and also generates new shape parameters. A case study of three sand populations is presented to show the pertinence of a new ‘equivalent roundness' parameter.