Skew angle estimation for printed and handwritten documents using the Wigner–Ville distribution

摘要

A skew estimation algorithm for printed and handwritten documents, based on the document's horizontal projection profile and its Wigner–Ville distribution, is presented. The proposed algorithm is able to correct skew angles that range between −89 and +89° detecting the right oriented position of the page by the alternations of the horizontal projection profile. It is able of processing successfully handwritten documents, even if they consist of non-parallel text lines. It deals with the presence of graphics, while a few text lines suffice for the application of the algorithm. Furthermore, the latter permits the use of only a part of the page for the skew estimation minimizing the computational complexity. The proposed algorithm was evaluated on a wide variety of pages (i.e. printed, handwritten, multi-column, application forms etc.) achieving a success rate of 100% within a confidence range of ±0.3°.