Skew Correction of Document Images Using Interline Cross-Correlation

An efficient algorithm is presented in this paper for correcting skew of text lines in scanned document images. In this method, the cross-correlation between two lines in the image with a fixed distance is calculated. The correlation functions for all pairs of lines in the image are accumulated. The shift for which the accumulated cross-correlation function takes the maximum is then used for determining the skew angle. The image is rotated in the opposite direction for skew correction. The correlation function can be calculated without multiplications for binary images, thus the algorithm can be very efficiently implemented. The method can be used directly for gray-scale and color images as well as binary images. It has been tested on scanned document images with good results.