Method for correcting geometric distortion of text image

Abstract

The invention provides a method for correcting geometric distortion of a text image. The method comprises the following steps of: extracting a text row, in a horizontal direction, of the text image, fitting the text row by using a B-spline curve to obtain a text row curve; estimating a vanishing point of a cylindrical surface straight bus, a text row tangent convergence line and a focal length parameter of a camera by using the tangent convergence symmetry of the text row curve; constructing latitude lines of an isometric grid for the fit text row curve by adopting a crossratio interpolation value; estimating a directrix of the cylindrical surface by using similar perspective projection transformation of the text row curve and constructing longitude lines of the isometric grid; estimatinga length-to-width ratio of the isometric grid by using the text row curves at the top end and the bottom end of the image; and mapping meshes of each isometric grid into a square grid through a deformation technology based on the grid to finish the correction of the geometric distortion of the text image. By the method, the problem that perspective distortion, nonlinear deformation distortion andcompound distortion of the perspective distortion and the nonlinear deformation distortion cannot be corrected at the same time in the prior art can be solved; therefore, total correction of the geometric distortion of the text image shot by the camera can be realized.

Description

technical field [0001] The invention belongs to the technical fields of digital image processing and computer vision, and in particular relates to a technology for completely correcting perspective distortion and geometric distortion of a text image captured by a camera. Background technique [0002] Compared with flatbed scanners, digital cameras have many unique advantages in acquiring text images, such as easy portability, fast response, and the ability to photograph documents from any angle. Due to these characteristics, digital cameras have been widely used in the construction of digital libraries, digitization of literature and classics, and text recognition. However, due to the perspective imaging principle of the camera, geometric deformations such as perspective distortion often exist in the captured text images. In addition, when a book page is photographed with a camera, the image is also geometrically distorted due to deformation of the page. These two distorti...

AI Technical Summary

Problems solved by technology

However, due to unavoidable estimation errors, defects such as cracks and overlaps often exist in the stitched images.

These defects greatly affect the visual effect of image correction

In addition, due to the combination of perspective distortion and nonlinear geometric deformation distortion, this technology cannot completely correct the geometric distortion existing in the image, and has the disadvantages of large correction residual error and complex algorithm.

[0010] To sum up, the existing text image geometric distortion correction technology is far from mature, and it is impossible to completely correct various types of distortions such as perspective distortion, nonlinear geometric distortion and the combination of the two in the image at the same time. In specific cases, distortion correction is performed under very strict prerequisites

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