Skew correction of business card images acquired in PDA

An efficient algorithm for rotational skew correction of business card images acquired in a PDA (personal digital assistant) camera is presented. The proposed method is composed of four parts: block adaptive binarisation (BAB), stripe generation, skew angle calculation and image rotation. In BAB, an input image is binarised block by block so as to lessen the effects of irregular illumination and shadow over the input image. In stripe generation, character string clusters are generated merging adjacent characters and their strings, and then only clusters useful for skew angle calculation are output as stripes. In skew angle calculation, the direction angles of the stripes are calculated using their central moments and then the skew angle of the input image is determined averaging the direction angles. In image rotation, the input image is rotated by the skew angle. Experimental results show that the proposed method yields root mean square error of 0.44° for test images of several types of business cards acquired by a PDA under various surrounding conditions.

[1]  Andreas Dengel,et al.  ANASTASIL: A System for Low-Level and High-Level Geometric Analysis of Printed Documents , 1992 .

[2]  Guangshun Shi,et al.  A system for automatic Chinese business card recognition , 2001, Proceedings of Sixth International Conference on Document Analysis and Recognition.

[3]  Jae S. Lim,et al.  Two-Dimensional Signal and Image Processing , 1989 .

[4]  Hong Yan,et al.  Skew Correction of Document Images Using Interline Cross-Correlation , 1993, CVGIP Graph. Model. Image Process..

[5]  S. Chaudhuri,et al.  Robust detection of skew in document images , 1997, IEEE Trans. Image Process..

[6]  Maurizio Pilu,et al.  Extraction of illusory linear clues in perspectively skewed documents , 2001, Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001.

[7]  Majid Mirmehdi,et al.  Rectifying perspective views of text in 3D scenes using vanishing points , 2003, Pattern Recognit..

[8]  Nam Chul Kim,et al.  Block adaptive binarization of business card images in PDA using modified quadratic filter , 2003, IS&T/SPIE Electronic Imaging.

[9]  N. Otsu.  A threshold selection method from gray level histograms , 1979 .

[10]  Harry Wechsler,et al.  Automated page orientation and skew angle detection for binary document images , 1994, Pattern Recognit..

[11]  Maurizio Pilu,et al.  A light-weight text image processing method for handheld embedded cameras , 2002, BMVC.

[12]  Linda G. Shapiro,et al.  Computer Vision , 2001 .

[13]  S. H. Kim,et al.  Efficient skew estimation and correction algorithm for document images , 2002, Image Vis. Comput..

[14]  Yang Cao,et al.  Skew detection and correction in document images bsed on straight-line fitting , 2003, Pattern Recognit. Lett..