When a document is fed to a scanner for digitization, it suffers from some degrees of skew. This skew has a detrimental effect on character recognition. In this paper we present two novel skew estimation methods for scanned Persian documents that estimates skew angles based on the wavelet decompositions and projection profile analysis. In the first algorithm, one row of the skewed document images is selected and is decomposed by the wavelet transform and in the second algorithm the whole document image is decomposed. Then, in both algorithms the matrix containing the absolute values of the horizontal sub-band coefficients, is then rotated through a range of angles. A projection profile is computed at each angle, and the angle that maximizes the maximum projection profile is regarded as the skew angle. The first algorithm is used for limited angle but second algorithm is used for wide angles.

Date Published: 8 July 2011
PDF: 5 pages
Proc. SPIE 8009, Third International Conference on Digital Image Processing (ICDIP 2011), 80091A (8 July 2011); doi: 10.1117/12.896301

Published in SPIE Proceedings Vol. 8009:
Third International Conference on Digital Image Processing (ICDIP 2011)
Ting Zhang, Editor(s)