TensorFlow如何实现车牌识别功能

这篇文章主要为大家展示了"TensorFlow如何实现车牌识别功能"，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下"TensorFlow如何实现车牌识别功能"这篇文章吧。

如何使用TensorFlow进行车牌识别，但是，当时采用的数据集是MNIST数字手写体，只能分类0-9共10个数字，无法分类省份简称和字母，局限性较大，无实际意义。

经过图像定位分割处理，博主收集了相关省份简称和26个字母的图片数据集，结合前述博文中贴出的python+TensorFlow代码，实现了完整的车牌识别功能。本着分享精神，在此送上全部代码和车牌数据集。

车牌数据集下载地址（约4000张图片）：tf_car_license_dataset_jb51.rar

省份简称训练+识别代码（保存文件名为train-license-province.py）（拷贝代码请务必注意python文本缩进，只要有一处缩进错误，就无法得到正确结果，或者出现异常）：

#!/usr/bin/python3.5# -*- coding: utf-8 -*-  import sysimport osimport timeimport random import numpy as npimport tensorflow as tf from PIL import Image  SIZE = 1280WIDTH = 32HEIGHT = 40NUM_CLASSES = 6iterations = 300 SAVER_DIR = "train-saver/province/" PROVINCES = ("京","闽","粤","苏","沪","浙")nProvinceIndex = 0 time_begin = time.time()  # 定义输入节点，对应于图片像素值矩阵集合和图片标签(即所代表的数字)x = tf.placeholder(tf.float32, shape=[None, SIZE])y_ = tf.placeholder(tf.float32, shape=[None, NUM_CLASSES]) x_image = tf.reshape(x, [-1, WIDTH, HEIGHT, 1])  # 定义卷积函数def conv_layer(inputs, W, b, conv_strides, kernel_size, pool_strides, padding):  L1_conv = tf.nn.conv2d(inputs, W, strides=conv_strides, padding=padding)  L1_relu = tf.nn.relu(L1_conv + b)  return tf.nn.max_pool(L1_relu, ksize=kernel_size, strides=pool_strides, padding='SAME') # 定义全连接层函数def full_connect(inputs, W, b):  return tf.nn.relu(tf.matmul(inputs, W) + b)  if __name__ =='__main__' and sys.argv[1]=='train':  # 第一次遍历图片目录是为了获取图片总数  input_count = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/training-set/chinese-characters/%s/' % i      # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        input_count += 1   # 定义对应维数和各维长度的数组  input_images = np.array([[0]*SIZE for i in range(input_count)])  input_labels = np.array([[0]*NUM_CLASSES for i in range(input_count)])   # 第二次遍历图片目录是为了生成图片数据和标签  index = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/training-set/chinese-characters/%s/' % i     # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        filename = dir + filename        img = Image.open(filename)        width = img.size[0]        height = img.size[1]        for h in range(0, height):          for w in range(0, width):            # 通过这样的处理，使数字的线条变细，有利于提高识别准确率            if img.getpixel((w, h)) > 230:              input_images[index][w+h*width] = 0            else:              input_images[index][w+h*width] = 1        input_labels[index][i] = 1        index += 1   # 第一次遍历图片目录是为了获取图片总数  val_count = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/validation-set/chinese-characters/%s/' % i      # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        val_count += 1   # 定义对应维数和各维长度的数组  val_images = np.array([[0]*SIZE for i in range(val_count)])  val_labels = np.array([[0]*NUM_CLASSES for i in range(val_count)])   # 第二次遍历图片目录是为了生成图片数据和标签  index = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/validation-set/chinese-characters/%s/' % i     # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        filename = dir + filename        img = Image.open(filename)        width = img.size[0]        height = img.size[1]        for h in range(0, height):          for w in range(0, width):            # 通过这样的处理，使数字的线条变细，有利于提高识别准确率            if img.getpixel((w, h)) > 230:              val_images[index][w+h*width] = 0            else:              val_images[index][w+h*width] = 1        val_labels[index][i] = 1        index += 1    with tf.Session() as sess:    # 第一个卷积层    W_conv1 = tf.Variable(tf.truncated_normal([8, 8, 1, 16], stddev=0.1), name="W_conv1")    b_conv1 = tf.Variable(tf.constant(0.1, shape=[16]), name="b_conv1")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 2, 2, 1]    pool_strides = [1, 2, 2, 1]    L1_pool = conv_layer(x_image, W_conv1, b_conv1, conv_strides, kernel_size, pool_strides, padding='SAME')     # 第二个卷积层    W_conv2 = tf.Variable(tf.truncated_normal([5, 5, 16, 32], stddev=0.1), name="W_conv2")    b_conv2 = tf.Variable(tf.constant(0.1, shape=[32]), name="b_conv2")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 1, 1, 1]    pool_strides = [1, 1, 1, 1]    L2_pool = conv_layer(L1_pool, W_conv2, b_conv2, conv_strides, kernel_size, pool_strides, padding='SAME')      # 全连接层    W_fc1 = tf.Variable(tf.truncated_normal([16 * 20 * 32, 512], stddev=0.1), name="W_fc1")    b_fc1 = tf.Variable(tf.constant(0.1, shape=[512]), name="b_fc1")    h_pool2_flat = tf.reshape(L2_pool, [-1, 16 * 20*32])    h_fc1 = full_connect(h_pool2_flat, W_fc1, b_fc1)      # dropout    keep_prob = tf.placeholder(tf.float32)     h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)      # readout层    W_fc2 = tf.Variable(tf.truncated_normal([512, NUM_CLASSES], stddev=0.1), name="W_fc2")    b_fc2 = tf.Variable(tf.constant(0.1, shape=[NUM_CLASSES]), name="b_fc2")     # 定义优化器和训练op    y_conv = tf.matmul(h_fc1_drop, W_fc2) + b_fc2    cross_entropy = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(labels=y_, logits=y_conv))    train_step = tf.train.AdamOptimizer((1e-4)).minimize(cross_entropy)     correct_prediction = tf.equal(tf.argmax(y_conv, 1), tf.argmax(y_, 1))    accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))     # 初始化saver    saver = tf.train.Saver()     sess.run(tf.global_variables_initializer())     time_elapsed = time.time() - time_begin    print("读取图片文件耗费时间：%d秒" % time_elapsed)    time_begin = time.time()     print ("一共读取了 %s 个训练图像， %s 个标签" % (input_count, input_count))     # 设置每次训练op的输入个数和迭代次数，这里为了支持任意图片总数，定义了一个余数remainder，譬如，如果每次训练op的输入个数为60，图片总数为150张，则前面两次各输入60张，最后一次输入30张（余数30）    batch_size = 60    iterations = iterations    batches_count = int(input_count / batch_size)    remainder = input_count % batch_size    print ("训练数据集分成 %s 批, 前面每批 %s 个数据，最后一批 %s 个数据" % (batches_count+1, batch_size, remainder))     # 执行训练迭代    for it in range(iterations):      # 这里的关键是要把输入数组转为np.array      for n in range(batches_count):        train_step.run(feed_dict={x: input_images[n*batch_size:(n+1)*batch_size], y_: input_labels[n*batch_size:(n+1)*batch_size], keep_prob: 0.5})      if remainder > 0:        start_index = batches_count * batch_size;        train_step.run(feed_dict={x: input_images[start_index:input_count-1], y_: input_labels[start_index:input_count-1], keep_prob: 0.5})       # 每完成五次迭代，判断准确度是否已达到100%，达到则退出迭代循环      iterate_accuracy = 0      if it%5 == 0:        iterate_accuracy = accuracy.eval(feed_dict={x: val_images, y_: val_labels, keep_prob: 1.0})        print ('第 %d 次训练迭代: 准确率 %0.5f%%' % (it, iterate_accuracy*100))        if iterate_accuracy >= 0.9999 and it >= 150:          break;     print ('完成训练!')    time_elapsed = time.time() - time_begin    print ("训练耗费时间：%d秒" % time_elapsed)    time_begin = time.time()     # 保存训练结果    if not os.path.exists(SAVER_DIR):      print ('不存在训练数据保存目录，现在创建保存目录')      os.makedirs(SAVER_DIR)    saver_path = saver.save(sess, "%smodel.ckpt"%(SAVER_DIR))   if __name__ =='__main__' and sys.argv[1]=='predict':  saver = tf.train.import_meta_graph("%smodel.ckpt.meta"%(SAVER_DIR))  with tf.Session() as sess:    model_file=tf.train.latest_checkpoint(SAVER_DIR)    saver.restore(sess, model_file)     # 第一个卷积层    W_conv1 = sess.graph.get_tensor_by_name("W_conv1:0")    b_conv1 = sess.graph.get_tensor_by_name("b_conv1:0")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 2, 2, 1]    pool_strides = [1, 2, 2, 1]    L1_pool = conv_layer(x_image, W_conv1, b_conv1, conv_strides, kernel_size, pool_strides, padding='SAME')     # 第二个卷积层    W_conv2 = sess.graph.get_tensor_by_name("W_conv2:0")    b_conv2 = sess.graph.get_tensor_by_name("b_conv2:0")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 1, 1, 1]    pool_strides = [1, 1, 1, 1]    L2_pool = conv_layer(L1_pool, W_conv2, b_conv2, conv_strides, kernel_size, pool_strides, padding='SAME')      # 全连接层    W_fc1 = sess.graph.get_tensor_by_name("W_fc1:0")    b_fc1 = sess.graph.get_tensor_by_name("b_fc1:0")    h_pool2_flat = tf.reshape(L2_pool, [-1, 16 * 20*32])    h_fc1 = full_connect(h_pool2_flat, W_fc1, b_fc1)      # dropout    keep_prob = tf.placeholder(tf.float32)     h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)      # readout层    W_fc2 = sess.graph.get_tensor_by_name("W_fc2:0")    b_fc2 = sess.graph.get_tensor_by_name("b_fc2:0")     # 定义优化器和训练op    conv = tf.nn.softmax(tf.matmul(h_fc1_drop, W_fc2) + b_fc2)     for n in range(1,2):      path = "test_images/%s.bmp" % (n)      img = Image.open(path)      width = img.size[0]      height = img.size[1]       img_data = [[0]*SIZE for i in range(1)]      for h in range(0, height):        for w in range(0, width):          if img.getpixel((w, h)) < 190:            img_data[0][w+h*width] = 1          else:            img_data[0][w+h*width] = 0            result = sess.run(conv, feed_dict = {x: np.array(img_data), keep_prob: 1.0})      max1 = 0      max2 = 0      max3 = 0      max1_index = 0      max2_index = 0      max3_index = 0      for j in range(NUM_CLASSES):        if result[0][j] > max1:          max1 = result[0][j]          max1_index = j          continue        if (result[0][j]>max2) and (result[0][j]<=max1):          max2 = result[0][j]          max2_index = j          continue        if (result[0][j]>max3) and (result[0][j]<=max2):          max3 = result[0][j]          max3_index = j          continue            nProvinceIndex = max1_index      print ("概率： [%s %0.2f%%]  [%s %0.2f%%]  [%s %0.2f%%]" % (PROVINCES[max1_index],max1*100, PROVINCES[max2_index],max2*100, PROVINCES[max3_index],max3*100))          print ("省份简称是: %s" % PROVINCES[nProvinceIndex])

城市代号训练+识别代码（保存文件名为train-license-letters.py）：

#!/usr/bin/python3.5# -*- coding: utf-8 -*-  import sysimport osimport timeimport random import numpy as npimport tensorflow as tf from PIL import Image  SIZE = 1280WIDTH = 32HEIGHT = 40NUM_CLASSES = 26iterations = 500 SAVER_DIR = "train-saver/letters/" LETTERS_DIGITS = ("A","B","C","D","E","F","G","H","J","K","L","M","N","P","Q","R","S","T","U","V","W","X","Y","Z","I","O")license_num = "" time_begin = time.time()  # 定义输入节点，对应于图片像素值矩阵集合和图片标签(即所代表的数字)x = tf.placeholder(tf.float32, shape=[None, SIZE])y_ = tf.placeholder(tf.float32, shape=[None, NUM_CLASSES]) x_image = tf.reshape(x, [-1, WIDTH, HEIGHT, 1])  # 定义卷积函数def conv_layer(inputs, W, b, conv_strides, kernel_size, pool_strides, padding):  L1_conv = tf.nn.conv2d(inputs, W, strides=conv_strides, padding=padding)  L1_relu = tf.nn.relu(L1_conv + b)  return tf.nn.max_pool(L1_relu, ksize=kernel_size, strides=pool_strides, padding='SAME') # 定义全连接层函数def full_connect(inputs, W, b):  return tf.nn.relu(tf.matmul(inputs, W) + b)  if __name__ =='__main__' and sys.argv[1]=='train':  # 第一次遍历图片目录是为了获取图片总数  input_count = 0  for i in range(0+10,NUM_CLASSES+10):    dir = './train_images/training-set/letters/%s/' % i      # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        input_count += 1   # 定义对应维数和各维长度的数组  input_images = np.array([[0]*SIZE for i in range(input_count)])  input_labels = np.array([[0]*NUM_CLASSES for i in range(input_count)])   # 第二次遍历图片目录是为了生成图片数据和标签  index = 0  for i in range(0+10,NUM_CLASSES+10):    dir = './train_images/training-set/letters/%s/' % i     # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        filename = dir + filename        img = Image.open(filename)        width = img.size[0]        height = img.size[1]        for h in range(0, height):          for w in range(0, width):            # 通过这样的处理，使数字的线条变细，有利于提高识别准确率            if img.getpixel((w, h)) > 230:              input_images[index][w+h*width] = 0            else:              input_images[index][w+h*width] = 1        #print ("i=%d, index=%d" % (i, index))        input_labels[index][i-10] = 1        index += 1   # 第一次遍历图片目录是为了获取图片总数  val_count = 0  for i in range(0+10,NUM_CLASSES+10):    dir = './train_images/validation-set/%s/' % i      # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        val_count += 1   # 定义对应维数和各维长度的数组  val_images = np.array([[0]*SIZE for i in range(val_count)])  val_labels = np.array([[0]*NUM_CLASSES for i in range(val_count)])   # 第二次遍历图片目录是为了生成图片数据和标签  index = 0  for i in range(0+10,NUM_CLASSES+10):    dir = './train_images/validation-set/%s/' % i     # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        filename = dir + filename        img = Image.open(filename)        width = img.size[0]        height = img.size[1]        for h in range(0, height):          for w in range(0, width):            # 通过这样的处理，使数字的线条变细，有利于提高识别准确率            if img.getpixel((w, h)) > 230:              val_images[index][w+h*width] = 0            else:              val_images[index][w+h*width] = 1        val_labels[index][i-10] = 1        index += 1    with tf.Session() as sess:    # 第一个卷积层    W_conv1 = tf.Variable(tf.truncated_normal([8, 8, 1, 16], stddev=0.1), name="W_conv1")    b_conv1 = tf.Variable(tf.constant(0.1, shape=[16]), name="b_conv1")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 2, 2, 1]    pool_strides = [1, 2, 2, 1]    L1_pool = conv_layer(x_image, W_conv1, b_conv1, conv_strides, kernel_size, pool_strides, padding='SAME')     # 第二个卷积层    W_conv2 = tf.Variable(tf.truncated_normal([5, 5, 16, 32], stddev=0.1), name="W_conv2")    b_conv2 = tf.Variable(tf.constant(0.1, shape=[32]), name="b_conv2")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 1, 1, 1]    pool_strides = [1, 1, 1, 1]    L2_pool = conv_layer(L1_pool, W_conv2, b_conv2, conv_strides, kernel_size, pool_strides, padding='SAME')      # 全连接层    W_fc1 = tf.Variable(tf.truncated_normal([16 * 20 * 32, 512], stddev=0.1), name="W_fc1")    b_fc1 = tf.Variable(tf.constant(0.1, shape=[512]), name="b_fc1")    h_pool2_flat = tf.reshape(L2_pool, [-1, 16 * 20*32])    h_fc1 = full_connect(h_pool2_flat, W_fc1, b_fc1)      # dropout    keep_prob = tf.placeholder(tf.float32)     h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)      # readout层    W_fc2 = tf.Variable(tf.truncated_normal([512, NUM_CLASSES], stddev=0.1), name="W_fc2")    b_fc2 = tf.Variable(tf.constant(0.1, shape=[NUM_CLASSES]), name="b_fc2")     # 定义优化器和训练op    y_conv = tf.matmul(h_fc1_drop, W_fc2) + b_fc2    cross_entropy = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(labels=y_, logits=y_conv))    train_step = tf.train.AdamOptimizer((1e-4)).minimize(cross_entropy)     correct_prediction = tf.equal(tf.argmax(y_conv, 1), tf.argmax(y_, 1))    accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))     sess.run(tf.global_variables_initializer())     time_elapsed = time.time() - time_begin    print("读取图片文件耗费时间：%d秒" % time_elapsed)    time_begin = time.time()     print ("一共读取了 %s 个训练图像， %s 个标签" % (input_count, input_count))     # 设置每次训练op的输入个数和迭代次数，这里为了支持任意图片总数，定义了一个余数remainder，譬如，如果每次训练op的输入个数为60，图片总数为150张，则前面两次各输入60张，最后一次输入30张（余数30）    batch_size = 60    iterations = iterations    batches_count = int(input_count / batch_size)    remainder = input_count % batch_size    print ("训练数据集分成 %s 批, 前面每批 %s 个数据，最后一批 %s 个数据" % (batches_count+1, batch_size, remainder))     # 执行训练迭代    for it in range(iterations):      # 这里的关键是要把输入数组转为np.array      for n in range(batches_count):        train_step.run(feed_dict={x: input_images[n*batch_size:(n+1)*batch_size], y_: input_labels[n*batch_size:(n+1)*batch_size], keep_prob: 0.5})      if remainder > 0:        start_index = batches_count * batch_size;        train_step.run(feed_dict={x: input_images[start_index:input_count-1], y_: input_labels[start_index:input_count-1], keep_prob: 0.5})       # 每完成五次迭代，判断准确度是否已达到100%，达到则退出迭代循环      iterate_accuracy = 0      if it%5 == 0:        iterate_accuracy = accuracy.eval(feed_dict={x: val_images, y_: val_labels, keep_prob: 1.0})        print ('第 %d 次训练迭代: 准确率 %0.5f%%' % (it, iterate_accuracy*100))        if iterate_accuracy >= 0.9999 and it >= iterations:          break;     print ('完成训练!')    time_elapsed = time.time() - time_begin    print ("训练耗费时间：%d秒" % time_elapsed)    time_begin = time.time()     # 保存训练结果    if not os.path.exists(SAVER_DIR):      print ('不存在训练数据保存目录，现在创建保存目录')      os.makedirs(SAVER_DIR)    # 初始化saver    saver = tf.train.Saver()          saver_path = saver.save(sess, "%smodel.ckpt"%(SAVER_DIR))   if __name__ =='__main__' and sys.argv[1]=='predict':  saver = tf.train.import_meta_graph("%smodel.ckpt.meta"%(SAVER_DIR))  with tf.Session() as sess:    model_file=tf.train.latest_checkpoint(SAVER_DIR)    saver.restore(sess, model_file)     # 第一个卷积层    W_conv1 = sess.graph.get_tensor_by_name("W_conv1:0")    b_conv1 = sess.graph.get_tensor_by_name("b_conv1:0")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 2, 2, 1]    pool_strides = [1, 2, 2, 1]    L1_pool = conv_layer(x_image, W_conv1, b_conv1, conv_strides, kernel_size, pool_strides, padding='SAME')     # 第二个卷积层    W_conv2 = sess.graph.get_tensor_by_name("W_conv2:0")    b_conv2 = sess.graph.get_tensor_by_name("b_conv2:0")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 1, 1, 1]    pool_strides = [1, 1, 1, 1]    L2_pool = conv_layer(L1_pool, W_conv2, b_conv2, conv_strides, kernel_size, pool_strides, padding='SAME')      # 全连接层    W_fc1 = sess.graph.get_tensor_by_name("W_fc1:0")    b_fc1 = sess.graph.get_tensor_by_name("b_fc1:0")    h_pool2_flat = tf.reshape(L2_pool, [-1, 16 * 20*32])    h_fc1 = full_connect(h_pool2_flat, W_fc1, b_fc1)      # dropout    keep_prob = tf.placeholder(tf.float32)     h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)      # readout层    W_fc2 = sess.graph.get_tensor_by_name("W_fc2:0")    b_fc2 = sess.graph.get_tensor_by_name("b_fc2:0")     # 定义优化器和训练op    conv = tf.nn.softmax(tf.matmul(h_fc1_drop, W_fc2) + b_fc2)     for n in range(2,3):      path = "test_images/%s.bmp" % (n)      img = Image.open(path)      width = img.size[0]      height = img.size[1]       img_data = [[0]*SIZE for i in range(1)]      for h in range(0, height):        for w in range(0, width):          if img.getpixel((w, h)) < 190:            img_data[0][w+h*width] = 1          else:            img_data[0][w+h*width] = 0            result = sess.run(conv, feed_dict = {x: np.array(img_data), keep_prob: 1.0})            max1 = 0      max2 = 0      max3 = 0      max1_index = 0      max2_index = 0      max3_index = 0      for j in range(NUM_CLASSES):        if result[0][j] > max1:          max1 = result[0][j]          max1_index = j          continue        if (result[0][j]>max2) and (result[0][j]<=max1):          max2 = result[0][j]          max2_index = j          continue        if (result[0][j]>max3) and (result[0][j]<=max2):          max3 = result[0][j]          max3_index = j          continue            if n == 3:        license_num += "-"      license_num = license_num + LETTERS_DIGITS[max1_index]      print ("概率： [%s %0.2f%%]  [%s %0.2f%%]  [%s %0.2f%%]" % (LETTERS_DIGITS[max1_index],max1*100, LETTERS_DIGITS[max2_index],max2*100, LETTERS_DIGITS[max3_index],max3*100))          print ("城市代号是: 【%s】" % license_num)

车牌编号训练+识别代码（保存文件名为train-license-digits.py）：

#!/usr/bin/python3.5# -*- coding: utf-8 -*-  import sysimport osimport timeimport random import numpy as npimport tensorflow as tf from PIL import Image  SIZE = 1280WIDTH = 32HEIGHT = 40NUM_CLASSES = 34iterations = 1000 SAVER_DIR = "train-saver/digits/" LETTERS_DIGITS = ("0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F","G","H","J","K","L","M","N","P","Q","R","S","T","U","V","W","X","Y","Z")license_num = "" time_begin = time.time()  # 定义输入节点，对应于图片像素值矩阵集合和图片标签(即所代表的数字)x = tf.placeholder(tf.float32, shape=[None, SIZE])y_ = tf.placeholder(tf.float32, shape=[None, NUM_CLASSES]) x_image = tf.reshape(x, [-1, WIDTH, HEIGHT, 1])  # 定义卷积函数def conv_layer(inputs, W, b, conv_strides, kernel_size, pool_strides, padding):  L1_conv = tf.nn.conv2d(inputs, W, strides=conv_strides, padding=padding)  L1_relu = tf.nn.relu(L1_conv + b)  return tf.nn.max_pool(L1_relu, ksize=kernel_size, strides=pool_strides, padding='SAME') # 定义全连接层函数def full_connect(inputs, W, b):  return tf.nn.relu(tf.matmul(inputs, W) + b)  if __name__ =='__main__' and sys.argv[1]=='train':  # 第一次遍历图片目录是为了获取图片总数  input_count = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/training-set/%s/' % i      # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        input_count += 1   # 定义对应维数和各维长度的数组  input_images = np.array([[0]*SIZE for i in range(input_count)])  input_labels = np.array([[0]*NUM_CLASSES for i in range(input_count)])   # 第二次遍历图片目录是为了生成图片数据和标签  index = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/training-set/%s/' % i     # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        filename = dir + filename        img = Image.open(filename)        width = img.size[0]        height = img.size[1]        for h in range(0, height):          for w in range(0, width):            # 通过这样的处理，使数字的线条变细，有利于提高识别准确率            if img.getpixel((w, h)) > 230:              input_images[index][w+h*width] = 0            else:              input_images[index][w+h*width] = 1        input_labels[index][i] = 1        index += 1   # 第一次遍历图片目录是为了获取图片总数  val_count = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/validation-set/%s/' % i      # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        val_count += 1   # 定义对应维数和各维长度的数组  val_images = np.array([[0]*SIZE for i in range(val_count)])  val_labels = np.array([[0]*NUM_CLASSES for i in range(val_count)])   # 第二次遍历图片目录是为了生成图片数据和标签  index = 0  for i in range(0,NUM_CLASSES):    dir = './train_images/validation-set/%s/' % i     # 这里可以改成你自己的图片目录，i为分类标签    for rt, dirs, files in os.walk(dir):      for filename in files:        filename = dir + filename        img = Image.open(filename)        width = img.size[0]        height = img.size[1]        for h in range(0, height):          for w in range(0, width):            # 通过这样的处理，使数字的线条变细，有利于提高识别准确率            if img.getpixel((w, h)) > 230:              val_images[index][w+h*width] = 0            else:              val_images[index][w+h*width] = 1        val_labels[index][i] = 1        index += 1    with tf.Session() as sess:    # 第一个卷积层    W_conv1 = tf.Variable(tf.truncated_normal([8, 8, 1, 16], stddev=0.1), name="W_conv1")    b_conv1 = tf.Variable(tf.constant(0.1, shape=[16]), name="b_conv1")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 2, 2, 1]    pool_strides = [1, 2, 2, 1]    L1_pool = conv_layer(x_image, W_conv1, b_conv1, conv_strides, kernel_size, pool_strides, padding='SAME')     # 第二个卷积层    W_conv2 = tf.Variable(tf.truncated_normal([5, 5, 16, 32], stddev=0.1), name="W_conv2")    b_conv2 = tf.Variable(tf.constant(0.1, shape=[32]), name="b_conv2")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 1, 1, 1]    pool_strides = [1, 1, 1, 1]    L2_pool = conv_layer(L1_pool, W_conv2, b_conv2, conv_strides, kernel_size, pool_strides, padding='SAME')      # 全连接层    W_fc1 = tf.Variable(tf.truncated_normal([16 * 20 * 32, 512], stddev=0.1), name="W_fc1")    b_fc1 = tf.Variable(tf.constant(0.1, shape=[512]), name="b_fc1")    h_pool2_flat = tf.reshape(L2_pool, [-1, 16 * 20*32])    h_fc1 = full_connect(h_pool2_flat, W_fc1, b_fc1)      # dropout    keep_prob = tf.placeholder(tf.float32)     h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)      # readout层    W_fc2 = tf.Variable(tf.truncated_normal([512, NUM_CLASSES], stddev=0.1), name="W_fc2")    b_fc2 = tf.Variable(tf.constant(0.1, shape=[NUM_CLASSES]), name="b_fc2")     # 定义优化器和训练op    y_conv = tf.matmul(h_fc1_drop, W_fc2) + b_fc2    cross_entropy = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(labels=y_, logits=y_conv))    train_step = tf.train.AdamOptimizer((1e-4)).minimize(cross_entropy)     correct_prediction = tf.equal(tf.argmax(y_conv, 1), tf.argmax(y_, 1))    accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))     sess.run(tf.global_variables_initializer())     time_elapsed = time.time() - time_begin    print("读取图片文件耗费时间：%d秒" % time_elapsed)    time_begin = time.time()     print ("一共读取了 %s 个训练图像， %s 个标签" % (input_count, input_count))     # 设置每次训练op的输入个数和迭代次数，这里为了支持任意图片总数，定义了一个余数remainder，譬如，如果每次训练op的输入个数为60，图片总数为150张，则前面两次各输入60张，最后一次输入30张（余数30）    batch_size = 60    iterations = iterations    batches_count = int(input_count / batch_size)    remainder = input_count % batch_size    print ("训练数据集分成 %s 批, 前面每批 %s 个数据，最后一批 %s 个数据" % (batches_count+1, batch_size, remainder))     # 执行训练迭代    for it in range(iterations):      # 这里的关键是要把输入数组转为np.array      for n in range(batches_count):        train_step.run(feed_dict={x: input_images[n*batch_size:(n+1)*batch_size], y_: input_labels[n*batch_size:(n+1)*batch_size], keep_prob: 0.5})      if remainder > 0:        start_index = batches_count * batch_size;        train_step.run(feed_dict={x: input_images[start_index:input_count-1], y_: input_labels[start_index:input_count-1], keep_prob: 0.5})       # 每完成五次迭代，判断准确度是否已达到100%，达到则退出迭代循环      iterate_accuracy = 0      if it%5 == 0:        iterate_accuracy = accuracy.eval(feed_dict={x: val_images, y_: val_labels, keep_prob: 1.0})        print ('第 %d 次训练迭代: 准确率 %0.5f%%' % (it, iterate_accuracy*100))        if iterate_accuracy >= 0.9999 and it >= iterations:          break;     print ('完成训练!')    time_elapsed = time.time() - time_begin    print ("训练耗费时间：%d秒" % time_elapsed)    time_begin = time.time()     # 保存训练结果    if not os.path.exists(SAVER_DIR):      print ('不存在训练数据保存目录，现在创建保存目录')      os.makedirs(SAVER_DIR)    # 初始化saver    saver = tf.train.Saver()          saver_path = saver.save(sess, "%smodel.ckpt"%(SAVER_DIR))   if __name__ =='__main__' and sys.argv[1]=='predict':  saver = tf.train.import_meta_graph("%smodel.ckpt.meta"%(SAVER_DIR))  with tf.Session() as sess:    model_file=tf.train.latest_checkpoint(SAVER_DIR)    saver.restore(sess, model_file)     # 第一个卷积层    W_conv1 = sess.graph.get_tensor_by_name("W_conv1:0")    b_conv1 = sess.graph.get_tensor_by_name("b_conv1:0")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 2, 2, 1]    pool_strides = [1, 2, 2, 1]    L1_pool = conv_layer(x_image, W_conv1, b_conv1, conv_strides, kernel_size, pool_strides, padding='SAME')     # 第二个卷积层    W_conv2 = sess.graph.get_tensor_by_name("W_conv2:0")    b_conv2 = sess.graph.get_tensor_by_name("b_conv2:0")    conv_strides = [1, 1, 1, 1]    kernel_size = [1, 1, 1, 1]    pool_strides = [1, 1, 1, 1]    L2_pool = conv_layer(L1_pool, W_conv2, b_conv2, conv_strides, kernel_size, pool_strides, padding='SAME')      # 全连接层    W_fc1 = sess.graph.get_tensor_by_name("W_fc1:0")    b_fc1 = sess.graph.get_tensor_by_name("b_fc1:0")    h_pool2_flat = tf.reshape(L2_pool, [-1, 16 * 20*32])    h_fc1 = full_connect(h_pool2_flat, W_fc1, b_fc1)      # dropout    keep_prob = tf.placeholder(tf.float32)     h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)      # readout层    W_fc2 = sess.graph.get_tensor_by_name("W_fc2:0")    b_fc2 = sess.graph.get_tensor_by_name("b_fc2:0")     # 定义优化器和训练op    conv = tf.nn.softmax(tf.matmul(h_fc1_drop, W_fc2) + b_fc2)     for n in range(3,8):      path = "test_images/%s.bmp" % (n)      img = Image.open(path)      width = img.size[0]      height = img.size[1]       img_data = [[0]*SIZE for i in range(1)]      for h in range(0, height):        for w in range(0, width):          if img.getpixel((w, h)) < 190:            img_data[0][w+h*width] = 1          else:            img_data[0][w+h*width] = 0            result = sess.run(conv, feed_dict = {x: np.array(img_data), keep_prob: 1.0})            max1 = 0      max2 = 0      max3 = 0      max1_index = 0      max2_index = 0      max3_index = 0      for j in range(NUM_CLASSES):        if result[0][j] > max1:          max1 = result[0][j]          max1_index = j          continue        if (result[0][j]>max2) and (result[0][j]<=max1):          max2 = result[0][j]          max2_index = j          continue        if (result[0][j]>max3) and (result[0][j]<=max2):          max3 = result[0][j]          max3_index = j          continue            license_num = license_num + LETTERS_DIGITS[max1_index]      print ("概率： [%s %0.2f%%]  [%s %0.2f%%]  [%s %0.2f%%]" % (LETTERS_DIGITS[max1_index],max1*100, LETTERS_DIGITS[max2_index],max2*100, LETTERS_DIGITS[max3_index],max3*100))          print ("车牌编号是: 【%s】" % license_num)

保存好上面三个python脚本后，我们首先进行省份简称训练。在运行代码之前，需要先把数据集解压到训练脚本所在目录。然后，在命令行中进入脚本所在目录，输入执行如下命令：

python train-license-province.py train

训练结果如下：

然后进行省份简称识别，在命令行输入执行如下命令：

python train-license-province.py predict

执行城市代号训练（相当于训练26个字母）：

python train-license-letters.py train

识别城市代号：

python train-license-letters.py predict

执行车牌编号训练（相当于训练24个字母+10个数字，我国交通法规规定车牌编号中不包含字母I和O）：

python train-license-digits.py train

识别车牌编号：

python train-license-digits.py predict

可以看到，在测试图片上，识别准确率很高。识别结果是闽O-1672Q。

下图是测试图片的车牌原图：

以上是"TensorFlow如何实现车牌识别功能"这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注行业资讯频道！