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本文基于机器学习的车牌识别系统的工作主要是运用SVM算法实现了对车牌的识别,支持上传本地图片和调用摄像头进行拍摄两种识别的途径。并用tkinter做了一个客户端界面。
该算法主要的思想是先使用图像边缘和车牌颜色定位车牌,再用SVM算法识别字符。车牌定位在predict方法中,为说明清楚,完成代码和测试后,加了很多注释,请参看源码。车牌字符识别也在predict方法中,请参看源码中的注释,需要说明的是,车牌字符识别使用的算法是opencv的SVM, opencv的SVM使用代码来自于opencv附带的sample,StatModel类和SVM类都是sample中的代码。SVM训练使用的训练样本来自于github上的EasyPR的c++版本。源码中,上传了EasyPR中的训练样本,在train\目录下,如果要重新训练请解压在当前目录下,并删除原始训练数据文件svm.dat和svmchinese.dat。#以上为车牌定位 #以下为识别车牌中的字符 predict_result = [] roi = None card_color = None for i, color in enumerate(colors): if color in ("blue", "yello", "green"): card_img = card_imgs[i] gray_img = cv2.cvtColor(card_img, cv2.COLOR_BGR2GRAY) #黄、绿车牌字符比背景暗、与蓝车牌刚好相反,所以黄、绿车牌需要反向 if color == "green" or color == "yello": gray_img = cv2.bitwise_not(gray_img) ret, gray_img = cv2.threshold(gray_img, 0, 255, cv2.THRESH_BINARY + cv2.THRESH_OTSU) #查找水平直方图波峰 x_histogram = np.sum(gray_img, axis=1) x_min = np.min(x_histogram) x_average = np.sum(x_histogram)/x_histogram.shape[0] x_threshold = (x_min + x_average)/2 wave_peaks = find_waves(x_threshold, x_histogram) if len(wave_peaks) == 0: print("peak less 0:") continue #认为水平方向,最大的波峰为车牌区域 wave = max(wave_peaks, key=lambda x:x[1]-x[0]) gray_img = gray_img[wave[0]:wave[1]] #查找垂直直方图波峰 row_num, col_num= gray_img.shape[:2] #去掉车牌上下边缘1个像素,避免白边影响阈值判断 gray_img = gray_img[1:row_num-1] y_histogram = np.sum(gray_img, axis=0) y_min = np.min(y_histogram) y_average = np.sum(y_histogram)/y_histogram.shape[0] y_threshold = (y_min + y_average)/5#U和0要求阈值偏小,否则U和0会被分成两半 wave_peaks = find_waves(y_threshold, y_histogram) #for wave in wave_peaks: # cv2.line(card_img, pt1=(wave[0], 5), pt2=(wave[1], 5), color=(0, 0, 255), thickness=2) #车牌字符数应大于6 if len(wave_peaks) <= 6: print("peak less 1:", len(wave_peaks)) continue wave = max(wave_peaks, key=lambda x:x[1]-x[0]) max_wave_dis = wave[1] - wave[0] #判断是否是左侧车牌边缘 if wave_peaks[0][1] - wave_peaks[0][0] < max_wave_dis/3 and wave_peaks[0][0] == 0: wave_peaks.pop(0) #组合分离汉字 cur_dis = 0 for i,wave in enumerate(wave_peaks): if wave[1] - wave[0] + cur_dis > max_wave_dis * 0.6: break else: cur_dis += wave[1] - wave[0] if i > 0: wave = (wave_peaks[0][0], wave_peaks[i][1]) wave_peaks = wave_peaks[i+1:] wave_peaks.insert(0, wave) #去除车牌上的分隔点 point = wave_peaks[2] if point[1] - point[0] < max_wave_dis/3: point_img = gray_img[:,point[0]:point[1]] if np.mean(point_img) < 255/5: wave_peaks.pop(2) if len(wave_peaks) <= 6: print("peak less 2:", len(wave_peaks)) continue part_cards = seperate_card(gray_img, wave_peaks) for i, part_card in enumerate(part_cards): #可能是固定车牌的铆钉 if np.mean(part_card) < 255/5: print("a point") continue part_card_old = part_card #w = abs(part_card.shape[1] - SZ)//2 w = part_card.shape[1] // 3 part_card = cv2.copyMakeBorder(part_card, 0, 0, w, w, cv2.BORDER_CONSTANT, value = [0,0,0]) part_card = cv2.resize(part_card, (SZ, SZ), interpolation=cv2.INTER_AREA) #cv2.imshow("part", part_card_old) #cv2.waitKey(0) #cv2.imwrite("u.jpg", part_card) #part_card = deskew(part_card) part_card = preprocess_hog([part_card]) if i == 0: resp = self.modelchinese.predict(part_card) charactor = provinces[int(resp[0]) - PROVINCE_START] else: resp = self.model.predict(part_card) charactor = chr(resp[0]) #判断最后一个数是否是车牌边缘,假设车牌边缘被认为是1 if charactor == "1" and i == len(part_cards)-1: if part_card_old.shape[0]/part_card_old.shape[1] >= 8:#1太细,认为是边缘 print(part_card_old.shape) continue predict_result.append(charactor) roi = card_img card_color = color break return predict_result, roi, card_color#识别到的字符、定位的车牌图像、车牌颜色
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