Low-complexity arrays of patch signature for efficient ancient coin retrieval

We present a new recognition framework for ancient coins struck from the same die. It is called Low-complexity Arrays of Patch Signatures. To overcome the problem of illumination conditions we use multi-light energy maps which are a light-independent, 2.5D representation of the coin. The coin recognition is based on a local texture analysis of the energy maps. Descriptors of patches, tailored to coin images via the properties provided by the energy map, are matched against a database using a system of associative arrays. The system of associative arrays used for the matching is a generalization of the Low-complexity Arrays of Contour Signatures. Hence, the matching is very efficient and nearly at constant time. Due to the lack of available data, we present two new data sets of artificial and real ancient coins respectively. Theoretical insights for the framework are discussed and various experiments demonstrate the promising efficiency of our method.