Signature features represent magnitudes that are extracted from digitized signature samples, with the aim of describing each signature as a vector of values. The extraction and selection of optimum signature features is a crucial step when designing a verification system. Features must allow each signature to be described in a way that the discriminative power between signatures produced by different users is maximized while allowing variability among signatures from the same user.
Online signature features can be divided into two main types. Global features model the signature as a holistic multidimensional vector and represent magnitudes such as average speed, total duration, and aspect ratio. On the other hand, local features are time functions derived from the signals, such as the pen-position coordinate sequence or pressure signals, captured with digitizing tablets or touch screens.
In off-line signature verification systems, features...
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