Nonparametric Illumination and Skew Correction for Scanned Document Images

A scanned image of an document page most often suffers from various scanning artifacts known as scanning shading and dark borders noises. These artifacts will degrade the qualities of the scanned images and causes problems to the subsequent process of document image analysis. My research work is based on effective method to rectify these scanning artifacts. This method comes from two observations: that the shading surface of most scanned book pages is quasi-concave and that the document contents are usually printed on a sheet of plain and bright paper. Based on these observations, a shading image can be accurately extracted via convex hulls-based image reconstruction. The proposed method proves to be surprisingly effective for image shading correction, dark borders removal and also for skew correction. It can restore a desired shading-free image and meanwhile yield an illumination surface of high quality. The performance will be evaluated by comparing all other state of art algorithms.