关键词: 车牌识别, 二值化, 阈值, 最大类间方差法, 最大熵法, 图像直方图

Abstract: During the research for the license plate recognition based on the Digital Image Processing Technology, because the location and segmentation of license plate are usually based on the binarized image, the image binaryzation is a key step, and the results of the image binaryzation will impact the location and segmentation directly. The most important part of the image binaryzation is the determination of threshold. In this paper, several methods have been compared, and also the basic principles and computer simulation results of inter-class varimax and maximum entropy method have been analyzed. But we have found that these methods are not optional when used to process vehicle license plate images. Therefore, a new method has been put forward, which is the arithmetic of license plate image binarization based on image histogram. Experiments have proven that this arithmetic is optimal when used to process vehicle license plate images.

Key words: license plate recognition, binaryzation, threshold, interclass varimax, maximum entropy method, image histogram