A Simple Approach Of Document Image Rectification

With the development of science and technology,people usually would like to digitize information printed on the paper.The most commons are books,newspapers,magazines which can be digitized by a scanner though the process of scanning.However,a scanner need manual operation and it is too large to carry.With cameras becoming more and more popular,digitize printed documents using a camera has become a trend.However document images scanned by a scanner are different from the ones captured by a camera.Camera captured document images have two types of distortions.One is physical distortion caused by the bending of document surface,and the other is perspective distortion caused by the formation of the image.These two types of distortions not only will affect the visual effect of the document image,but also influence the Optical Character Recognition result.Therefore it is important to rectify camera captured document images and to make it looks like the ones scanned by a scanner.This paper,based on a comprehensive inspection of related work,proposed a new method to rectify document image.Firstly,the proposed method does not need additional hardware,such as distance sensor or laser beam.The proposed method only need a sheet of paper with some patterns printed on it.Secondly,the proposed method does not need multiple images nor the lighting assumption nor the given boundaries.The proposed method which utilize the technique of active contour,only need the color of document paper is white.Finally,the proposed method is independent of document content and do not need texts.The proposed method extract document boundaries and rectify the image by projective transformation.The major work of this paper are:1.This paper design a pattern printed on a sheet of paper.On the top and bottom of the paper are checkerboards and on the middle of it is a grid.The users only need to put the book on some position of the grid.2.This paper proposed a coarse-to-fine method do extract document boundaries with the help of active contour.3.This paper proposed a height calculation method to calculate the height of document boundaries with the help of camera calibration.4.This paper proposed a method to refine document page and to delete unrelated parts of the document pages.5.This paper rectify document images to eliminate both physical distortion and perspective distortion and make the document images just like scanned ones.