Hyung-soo Ohk

A restoration method for distorted image scanned from a bound book

When a bound document such as a book is scanned or copied with a flat-bed scanner, there are two kinds of defects in the scanned image; the geometric and photometric distortion. The root cause of the defects is the imperfect contact between the book to be scanned and the scanner glass plate. The long gap between the book center and the glass plate causes the optical path from the surface of the book and the imaging unit(CCD/CIS) to be different from the optimal condition. In this paper, we propose a method for restoring bound document scan images without any additional information or sensor. We correct the bound document images based on the estimation of the boundary feature and background profile. Boundary Feature is obtained after calculating and analyzing the Minimum Boundary Rectangle which encloses the whole foreground contents with minimum size and the extracted feature is used for correcting geometric distortion; de-skew, warping, and page separation. Background profile is estimated from the gradient map and it is utilized to correct photometric distortion; exposure problem. Experimental results show effectiveness of our proposed method.