Vehicle license plate location using active learning AdaBoost algorithm and color feature
Article Text (Baidu Translation)
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摘要: 人工选取少量的车牌区域和非车牌区域, 采用积分图法快速提取Haar-like扩展特征, 构成初始训练样本。使用AdaBoost算法训练样本产生一个初始分类器, 经过主动学习过程, 产生一个用于车牌检测的强分类器。利用Cascade结构检测法进行车牌的粗定位, 通过提取边缘颜色对, 对候选区域进行验证, 实现车牌区域的精确定位。对不同光照条件及车牌污损等复杂情况下的车牌图像进行了定位测试。测试结果表明: 车牌的粗定位率和精确定位率分别为98.3%、97.1%, 平均定位时间小于0.1 s, 因此, 该方法有较好的车牌定位效果和定位准确率。Abstract: A small amount of license plate areas and non-license plate areas were selected, and Haar-like extended features were extracted by using the integration diagram method to obtain initial training samples. An initial classifier was generated by training the samples with AdaBoost algorithm. A strong classifier for license plate detection was obtained in the active learning procedure. The coarse location of license plate was implemented by using the cascade structure detection method. The candidate region was verified to get the precise location of license plate area by extracting edge-color pairs. The method was applied into the test of vehicle license plate location under different illumination and defaced circumstances. Test result indicates that the coarse location rate of license plate is 98.3%, the precise location rate is 97.1%, and the average location time is less than 0.1 s. A better license plate location effect and accuracy are achieved by the proposed method.
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表 1 车牌边缘颜色对
Table 1. Edge-color pairs of vehicle license plate
车牌 蓝牌 黄牌 白牌 黑牌 边缘颜色对 (1, 4) (2, 5) (3, 4)、(4, 5) (4, 5) -
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