diff --git a/advanced/license_plate_recog/image_operations.py b/advanced/license_plate_recog/image_operations.py new file mode 100644 index 0000000..9844067 --- /dev/null +++ b/advanced/license_plate_recog/image_operations.py @@ -0,0 +1,160 @@ +import cv2 +import os +import numpy as np +import pytesseract + + +def locate_license_plate(image_path): + if not os.path.isfile(image_path): + print(f"Error: File '{image_path}' does not exist.") + return None + + """ + 根据输入的图像路径,定位蓝色车牌并返回裁剪出的车牌区域 + """ + # 读取图像 + car = cv2.imread(image_path, 1) + + if car is None: + print(f"Error: Unable to read image '{image_path}'") + return None + + # 定义蓝色所对应的色彩空间范围 + lower_blue = np.array([100, 110, 110]) + upper_blue = np.array([130, 255, 255]) + + # 将图像转换到HSV颜色空间 + hsv = cv2.cvtColor(car, cv2.COLOR_BGR2HSV) + + # 获取蓝色区域的掩模 + mask_blue = cv2.inRange(hsv, lower_blue, upper_blue) + + # 将掩模转换为灰度图像 + mask = mask_blue + + # 形态学处理,开运算和闭运算 + matrix = np.ones((20, 20), np.uint8) + mask = cv2.morphologyEx(mask, cv2.MORPH_CLOSE, matrix) + mask = cv2.morphologyEx(mask, cv2.MORPH_OPEN, matrix) + + # 二值化 + ret, mask = cv2.threshold(mask, 0, 255, cv2.THRESH_BINARY) + + # 查找轮廓 + contours, hierarchy = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE) + + # 寻找最大轮廓并定位车牌 + max_area = 0 + best_contour = None + for contour in contours: + area = cv2.contourArea(contour) + if area > max_area: + max_area = area + best_contour = contour + + # 获取定位车牌的外接矩形框 + rect = cv2.minAreaRect(best_contour) + box = cv2.boxPoints(rect) + box = np.int32(box) + + # 获取旋转矩阵 + angle = rect[2] + flag = 0 + print(angle) + if angle < -45: + angle += 90 + flag = 1 + if angle > 45: + angle -= 90 + flag = 1 + print(angle) + center = (rect[0][0], rect[0][1]) + size = (int(rect[1][0]), int(rect[1][1])) + M = cv2.getRotationMatrix2D(center, angle, 1.0) + + # 旋转图像 + height, width = car.shape[:2] + rotated = cv2.warpAffine(car, M, (width, height)) + + # 获取旋转后矩形框的坐标 + if flag == 0: + box = cv2.boxPoints(((center[0], center[1]), (size[0], size[1]), 0.0)) + box = np.int32(box) + + # 裁剪车牌区域 + xs = [box[0, 0], box[1, 0], box[2, 0], box[3, 0]] + ys = [box[0, 1], box[1, 1], box[2, 1], box[3, 1]] + x1, x2 = min(xs), max(xs) + y1, y2 = min(ys), max(ys) + ROI_plate = rotated[y1:y2, x1:x2] + + return ROI_plate + + +def preprocess_image_for_ocr(image): + """ + 预处理图像以提高 OCR 识别率 + """ + # 去除左右上下各3个像素的边框 + height, width = image.shape[:2] + image = image[3:height - 3, 3:width - 3] + + # 调整图像大小到 165x40 + image = cv2.resize(image, (165, 40), interpolation=cv2.INTER_AREA) + + # 转换为灰度图像 + gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY) + + # 二值化 + _, binary = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY + cv2.THRESH_OTSU) + + # 去噪 + denoised = cv2.medianBlur(binary, 3) + + return denoised + + +def find_split_line(image): + """ + 在宽度15-30像素之间查找分割线 + """ + height, width = image.shape + column_sums = np.sum(image[3:height - 3, 15:30], axis=0) # 忽略顶部和底部的像素 + + zero_columns = np.where(column_sums == 0)[0] # 找到像素和为0的列 + if len(zero_columns) == 0: + # 如果没有找到和为0的列,返回默认分割线为22 + split_line = 22 + else: + # 计算零列的中值作为分割线 + split_line = int(np.median(zero_columns)) + 15 # 加上偏移量15 + print(split_line) + return split_line + + +def recognize_characters(image): + """ + 使用OCR技术识别车牌上的字符 + """ + preprocessed_image = preprocess_image_for_ocr(image) + + # 找到分割线 + split_line = find_split_line(preprocessed_image) + + # 切割图像为两部分 + part1 = preprocessed_image[:, :split_line] # 宽度0-split_line部分 + part2 = preprocessed_image[:, split_line:] # 剩余部分 + + # 调用 Tesseract OCR 识别宽度0-24部分 + custom_config_chi_sim = r'--oem 3 --psm 6 -l chi_sim' + result_chi_sim = pytesseract.image_to_string(part1, config=custom_config_chi_sim) + + # 调用 Tesseract OCR 识别剩余部分 + custom_config_default = r'--oem 3 --psm 6' + result_default = pytesseract.image_to_string(part2, config=custom_config_default) + + # 合并两个部分的识别结果 + recognized_characters = result_chi_sim.strip() + result_default.strip() + + return recognized_characters +