Exploiting Vector Fields for Geometric Rectification of Distorted Document Images

This paper proposes a segment-free method for geometric rectification of a distorted document image captured by a hand-held camera. The method can recover the 3D page shape by exploiting the intrinsic vector fields of the image. Based on the assumption that the curled page shape is a general cylindrical surface, we estimate the parameters related to the camera and the 3D shape model through weighted majority voting on the vector fields. Then the spatial directrix of the surface is recovered by solving an ordinary differential equation (ODE) through the Euler method. Finally, the geometric distortions in images can be rectified by flattening the estimated 3D page surface onto a plane. Our method can exploit diverse types of visual cues available in a distorted document image to estimate its vector fields for 3D page shape recovery. In comparison to the state-of-the-art methods, the great advantage is that it is a segment-free method and does not have to extract curved text lines or textual blocks, which is still a very challenging problem especially for a distorted document image. Our method can therefore be freely applied to document images with extremely complicated page layouts and severe image quality degradation. Extensive experiments are implemented to demonstrate the effectiveness of the proposed method.