A novel skew estimation approach using radon transform

Skew is the angle the image makes with the corner of the page. Skew estimation is a preprocessing step in document image analysis. It involves two steps skew detection and skew correction. Skew estimation is needed because while scanning the document image a little skew is unavoidable. If skew is present in the document then Optical Character Recognizer (OCR) will identify the script wrongly. In this paper an effective and reliable skew estimation technique using radon transform is proposed. Radon transform will take O(N2M) time to execute for a document image of size N X N and with the skew of M. The proposed technique is tested on 150 document images with skew varying from 1 to 25 degrees. The accuracy of identification is 100% and average time of execution is 2.23seconds.

[1]  Nanning Zheng,et al.  Skew Estimation of Document Images Using Bagging , 2010, IEEE Transactions on Image Processing.

[2]  Basanna V. Dhandra,et al.  Skew Detection in Binary Image Documents Based on Image Dilation and Region labeling Approach , 2006, 18th International Conference on Pattern Recognition (ICPR'06).

[3]  Robert M. Haralick,et al.  An automatic algorithm for text skew estimation in document images using recursive morphological transforms , 1994, Proceedings of 1st International Conference on Image Processing.

[4]  Neil W. Bergmann,et al.  Implementation of a statistical based Arabic character recognition system , 1997, TENCON '97 Brisbane - Australia. Proceedings of IEEE TENCON '97. IEEE Region 10 Annual Conference. Speech and Image Technologies for Computing and Telecommunications (Cat. No.97CH36162).

[5]  R. Bracewell.  Two-dimensional imaging , 1994 .

[6]  M. Sarfraz,et al.  Skew Estimation and Correction of Text Using Bounding Box , 2008, 2008 Fifth International Conference on Computer Graphics, Imaging and Visualisation.

[7]  Venu Govindaraju,et al.  Document image analysis: A primer , 2002 .

[8]  S. A. Shahab,et al.  A novel approach for skew estimation of document images in OCR system , 2005, International Conference on Computer Graphics, Imaging and Visualization (CGIV'05).

[9]  Jonathan J. Hull.  Document Image skew Detection: Survey and Annotated Bibliography , 1996, DAS.

[10]  Jorge Herbert de Lira,et al.  Two-Dimensional Signal and Image Processing , 1989 .