Straightening warped text lines using polynomial regression

Perspective distortion always occurs while scanning thick, bound documents, resulting in two problems in the scanned grayscale image: (i) shadow along the 'spine' of the book; (ii) warping of words in the shadow area. In our previous paper, we proposed a restoration system to solve these two problems (see Zheng Zhang and Chew Lim Tan, Int. Conf. on Image Proc., p.1074-7, 2001). However the shape of the warped words was not fully restored, since we simply shifted and rotated the warped word. We now propose a better method to straighten a warped text line using polynomial regression. The implementation results comparing with those of the old system show a marked improvement in the restoration of the image.