Camera-based document digitization using multiple images

Recently, there have been some attempts to use a portable digital camera for the document digitization. But unlike the conventional flatbed scanners, the document images taken by digital cameras suffer from the perspective distortion and the geometric distortion. These problems deteriorate not only the subjective quality but also the character recognition rate. In this paper, a new document dewarping algorithm that utilizes two input images is presented. The proposed algorithm requires neither auxiliary hardwares such that measure the 3D shape nor the impractical assumptions on the pose of books and cameras. Instead, the 3D shape of the book (document) surface is reconstructed from the geometric correspondence of two images and some post-processings. Contrast to the conventional works, the proposed algorithm do not need to find textlines. So it can be applied to not only text regions but also pictures, tables and mathematical equations. That is, we can rectify distorted images irrespective of languages or contents without auxiliary hardwares.