Skew detection using wavelet decomposition and projection profile analysis

In this paper, a novel document skew detection algorithm based on wavelet decompositions and projection profile analysis is proposed. First, the skewed document images are decomposed by the wavelet transform. The matrix containing the absolute values of the horizontal sub-band coefficients, which preserves the text’s horizontal structure, is then rotated through a range of angles. A projection profile is computed at each angle, and the angle that maximizes a criterion function is regarded as the skew angle. Experimental results show that this algorithm performs well on document images of various layouts and is also robust to different languages. The effects of various wavelet basis, number of decomposition levels, and parameters of the criterion function are investigated too.