Using the Median Distance to Compare Object Shapes in Content-Based Image Retrieval

Turning Angles (TAs) representation is considered one of the most interesting methods for representing object shapes in content-based image retrieval systems. Nevertheless, the distance commonly used to measure the similarity between shapes represented by TAs, the Euclidean one, is generally too sensitive to small variations in shapes.In this paper we present a new distance between shapes represented by TA, namely the Median distance, specially devised to minimize the effects of small variations in shapes. Its analytical properties are discussed and experimental results are provided and compared with those obtained by applying traditional techniques based on Euclidean distance. The Median distance has been implemented in the Automatic Image Storage and Retrieval (AISR) system, which allows storage and content-based retrieval of 2D images.