Geometric Distortion Correction of Camera Document Images using Skew Feature of Characters

D.G. Jang, Y.K. Chung, S.Y. Chi, and J. Soh (Korea)


Camera based document image, character recognition,geometric distortion, correction of distortion


When capturing a document image through a camera, a geometric distortion occurs because of deviation from an orthogonal and centered pose between the camera and a picturing document. This distortion makes a fatal problem in character recognition. Most of optical character recognition (OCR) systems are trained using orthogonal character images. Therefore, character features from the document images should be extracted from a recovered orthogonal rectangular shape of document images via some steps of image correction processes. Otherwise, the OCR systems do not correctly work. In this paper, we propose a method that can increase the performance of character recognition by correcting the geometric distortion of document images by using a bilinear transform. The proposed method can correct the geometric distortion using an only software method without a hardware device. Slopes of slanted characters and characteristics of a document image are used to recover the skewed images. After recovering an image, we can see the improved performance of character recognition in the experiments.

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