畸变汽车牌照图像的空间校正

首先针对我国汽车版照的常规模式，提出了用Hough变换提取牌照边框参数的方法，进而求得汽车牌照四边形区域4个顶点的坐标，并且给出了利用对极坐标参数表示的直线进行Hough变换的具体途径。然后，根据畸变牌照的4个顶点和归一化汽车牌照图像的4个顶点之间的一一对应关系，求解双线性空间变换方程，进而对畸变图像进行校正。最后给出了一种图像毛刺的剔除方法。实验表明，本文介绍了的方法对畸变牌照图像的归一化可以取得良好的效果。

Spatial Correction of the Distorted License Plate Image of Automobiles

According to the general style of automobile license plates in China, a method based on Hough transformation is proposed to acquire the parameters of four borders of the license plates. The coordinates of the four vertices of the quadrilateral plate are obtained, and a way to perform Hough transformation for lines in the polar coordinate system is also presented in detail. Then, the bilinear spatial transformation equations are solved according to the mapping between the four vertices of a distorted plate image and its normalized vertices, so as to correct the distorted plate image. Finally some smoothing procedures are used to erase the burrs of characters in the plate image. Experiment results show that with the method introduced in this paper the distorted license plate images can be well normalized.