Skeletal structures

Shape Descriptors are compact and expressive representations of objects suitable for solving problems like recognition, classification, or retrieval of shapes, tasks that are computationally expensive if performed on huge data sets. Skeletal structures are a particular class of shape descriptors, which attempt to quantify shapes in ways that agree with human intuition. In fact, they represent the essential structure of objects and the way basic components connect to form a whole. In the large amount of literature devoted to a wide variety of skeletal structures, this Chapter provides a concise and non-exhaustive introduction to the subject: indeed the first structural descriptor, the medial axis, dates back to 1967, which means forty years of literature on the topic.