Hee Kue Kwag, Soo Hyung Kim

The Transactions of the Korea Information Processing Society (1994 ~ 2000), Vol. 6, No. 11, pp. 3140-3149, Nov. 1999
10.3745/KIPSTE.1999.6.11.3140,   PDF Download:

Abstract

Skew correction for document images can be done using a rotational transformation of pixel coordinates. In this paper we propose a method when corrects the document skew, by an amount of %u03B8 degrees, using block information, where the block is defined as a rectangular area containing adjacent black pixels. Processing speed of the proposed method is faster than that of the method using pixel transformation, since the number of floating-point operations can be reduced significantly. In the proposed method, we rotate only the four corner points of each block, and then identify the pixels inside the block. Two methods for inside pixel identification are proposed; the first method finds two points intersecting the boundary of the rotated block in each raw, and determines the pixels between the two intersection points as the inside pixel. The second method finds boundary points based on Bresenham´s line drawing algorithm, using fixed-point operation, and fills the region surrounded by these boundaries as black pixels. We have measured the performance of the proposed method by experimenting it with 2,16 images of various English and Korean documents. We have also proven the superiority of our algorithm through performance comparison with respect to existing methods based on pixel transformation.

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