用PaddlePaddle进行车牌识别（二）

2018-04-12 16:10 观天下我要评论()

字号：T|T

上节我们讲了第一部分，如何用生成简易的车牌，这节课中我们会用PaddlePaddle来识别生成的车牌。

数据读取

在上一节生成车牌时，我们可以分别生成训练数据和测试数据，方法如下（完整代码在这里）：

1 # 将生成的车牌图片写入文件夹，对应的label写入label.txt

2 def genBatch(self, batchSize,pos,charRange, outputPath,size):

3 if (not os.path.exists(outputPath)):

4 os.mkdir(outputPath)

5 outfile = open('label.txt','w')

6 for i in xrange(batchSize):

7 plateStr,plate = G.genPlateString(-1,-1)

8 print plateStr,plate

9 img = G.generate(plateStr);

10 img = cv2.resize(img,size);

11 cv2.imwrite(outputPath + "/" + str(i).zfill(2) + ".jpg", img);

12 outfile.write(str(plate)+"\n")

生成好数据后，我们写一个reader来读取数据 ( reador.py )

1 def reader_creator(data,label):

2 def reader():

3 for i in xrange(len(data)):

4 yield data[i,:],int(label[i])

5 return reader

灌入模型时，我们需要调用paddle.batch函数，将数据shuffle后批量灌入模型中：

1 # 读取训练数据

2 train_reader = paddle.batch(paddle.reader.shuffle(

3 reador.reader_creator(X_train,Y_train),buf_size=200),

4 batch_size=16)

6 # 读取验证数据

7 val_reader = paddle.batch(paddle.reader.shuffle(

8 reador.reader_creator(X_val,Y_val),buf_size=200),

9 batch_size=16)

10 trainer.train(reader=train_reader,num_passes=20,event_handler=event_handler)

构建网络模型

因为我们训练的是端到端的车牌识别，所以一开始构建了两个卷积-池化层训练，训练完后同步训练7个全连接层，分别对应车牌的7位字符，最后将其拼接起来，与原始的label计算Softmax值，预测训练结果。　

1 def get_network_cnn(self):

2 # 加载data和label

3 x = paddle.layer.data(name='x', type=paddle.data_type.dense_vector(self.data))

4 y = paddle.layer.data(name='y', type=paddle.data_type.integer_value(self.label))

5 # 构建卷积-池化层-1

6 conv_pool_1 = paddle.networks.simple_img_conv_pool(

7 input=x,

8 filter_size=12,

9 num_filters=50,

10 num_channel=1,

11 pool_size=2,

12 pool_stride=2,

13 act=paddle.activation.Relu())

14 drop_1 = paddle.layer.dropout(input=conv_pool_1, dropout_rate=0.5)

15 # 构建卷积-池化层-2

16 conv_pool_2 = paddle.networks.simple_img_conv_pool(

17 input=drop_1,

18 filter_size=5,

19 num_filters=50,

20 num_channel=20,

21 pool_size=2,

22 pool_stride=2,

23 act=paddle.activation.Relu())

24 drop_2 = paddle.layer.dropout(input=conv_pool_2, dropout_rate=0.5)

26 # 全连接层

27 fc = paddle.layer.fc(input = drop_2, size = 120)

28 fc1_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

29 fc1 = paddle.layer.fc(input = fc1_drop,size = 65,act = paddle.activation.Linear())

31 fc2_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

32 fc2 = paddle.layer.fc(input = fc2_drop,size = 65,act = paddle.activation.Linear())

34 fc3_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

35 fc3 = paddle.layer.fc(input = fc3_drop,size = 65,act = paddle.activation.Linear())

37 fc4_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

38 fc4 = paddle.layer.fc(input = fc4_drop,size = 65,act = paddle.activation.Linear())

40 fc5_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

41 fc5 = paddle.layer.fc(input = fc5_drop,size = 65,act = paddle.activation.Linear())

43 fc6_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

44 fc6 = paddle.layer.fc(input = fc6_drop,size = 65,act = paddle.activation.Linear())

46 fc7_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

47 fc7 = paddle.layer.fc(input = fc7_drop,size = 65,act = paddle.activation.Linear())

49 # 将训练好的7个字符的全连接层拼接起来

50 fc_concat = paddle.layer.concact(input = [fc21, fc22, fc23, fc24,fc25,fc26,fc27], axis = 0)

51 predict = paddle.layer.classification_cost(input = fc_concat,label = y,act=paddle.activation.Softmax())

52 return predict

训练模型

构建好网络模型后，就是比较常见的步骤了，譬如初始化，定义优化方法，定义训练参数，定义训练器等等，再把第一步里我们写好的数据读取的方式放进去，就可以正常跑模型了。

1 class NeuralNetwork(object):

2 def __init__(self,X_train,Y_train,X_val,Y_val):

3 paddle.init(use_gpu = with_gpu,trainer_count=1)

5 self.X_train = X_train

6 self.Y_train = Y_train

7 self.X_val = X_val

8 self.Y_val = Y_val

11 def get_network_cnn(self):

13 x = paddle.layer.data(name='x', type=paddle.data_type.dense_vector(self.data))

14 y = paddle.layer.data(name='y', type=paddle.data_type.integer_value(self.label))

15 conv_pool_1 = paddle.networks.simple_img_conv_pool(

16 input=x,

17 filter_size=12,

18 num_filters=50,

19 num_channel=1,

20 pool_size=2,

21 pool_stride=2,

22 act=paddle.activation.Relu())

23 drop_1 = paddle.layer.dropout(input=conv_pool_1, dropout_rate=0.5)

24 conv_pool_2 = paddle.networks.simple_img_conv_pool(

25 input=drop_1,

26 filter_size=5,

27 num_filters=50,

28 num_channel=20,

29 pool_size=2,

30 pool_stride=2,

31 act=paddle.activation.Relu())

32 drop_2 = paddle.layer.dropout(input=conv_pool_2, dropout_rate=0.5)

34 fc = paddle.layer.fc(input = drop_2, size = 120)

35 fc1_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

36 fc1 = paddle.layer.fc(input = fc1_drop,size = 65,act = paddle.activation.Linear())

38 fc2_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

39 fc2 = paddle.layer.fc(input = fc2_drop,size = 65,act = paddle.activation.Linear())

41 fc3_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

42 fc3 = paddle.layer.fc(input = fc3_drop,size = 65,act = paddle.activation.Linear())

44 fc4_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

45 fc4 = paddle.layer.fc(input = fc4_drop,size = 65,act = paddle.activation.Linear())

47 fc5_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

48 fc5 = paddle.layer.fc(input = fc5_drop,size = 65,act = paddle.activation.Linear())

50 fc6_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

51 fc6 = paddle.layer.fc(input = fc6_drop,size = 65,act = paddle.activation.Linear())

53 fc7_drop = paddle.layer.dropout(input = fc,dropout_rate = 0.5)

54 fc7 = paddle.layer.fc(input = fc7_drop,size = 65,act = paddle.activation.Linear())

56 fc_concat = paddle.layer.concact(input = [fc21, fc22, fc23, fc24,fc25,fc26,fc27], axis = 0)

57 predict = paddle.layer.classification_cost(input = fc_concat,label = y,act=paddle.activation.Softmax())

58 return predict

60 # 定义训练器

61 def get_trainer(self):

63 cost = self.get_network()

65 #获取参数

66 parameters = paddle.parameters.create(cost)

69 optimizer = paddle.optimizer.Momentum(

70 momentum=0.9,

71 regularization=paddle.optimizer.L2Regularization(rate=0.0002 * 128),

72 learning_rate=0.001,

73 learning_rate_schedule = "pass_manual")

76 # 创建训练器

77 trainer = paddle.trainer.SGD(

78 cost=cost, parameters=parameters, update_equation=optimizer)

79 return trainer

82 # 开始训练

83 def start_trainer(self,X_train,Y_train,X_val,Y_val):

84 trainer = self.get_trainer()

86 result_lists = []

87 def event_handler(event):

88 if isinstance(event, paddle.event.EndIteration):

89 if event.batch_id % 10 == 0:

90 print "\nPass %d, Batch %d, Cost %f, %s" % (

91 event.pass_id, event.batch_id, event.cost, event.metrics)

92 if isinstance(event, paddle.event.EndPass):

93 # 保存训练好的参数

94 with open('params_pass_%d.tar' % event.pass_id, 'w') as f:

95 parameters.to_tar(f)

96 # feeding = ['x','y']

97 result = trainer.test(

98 reader=val_reader)

99 # feeding=feeding)

100 print "\nTest with Pass %d, %s" % (event.pass_id, result.metrics)

101

102 result_lists.append((event.pass_id, result.cost,

103 result.metrics['classification_error_evaluator']))

104

105 # 开始训练

106 train_reader = paddle.batch(paddle.reader.shuffle(

107 reador.reader_creator(X_train,Y_train),buf_size=200),

108 batch_size=16)

109

110 val_reader = paddle.batch(paddle.reader.shuffle(

111 reador.reader_creator(X_val,Y_val),buf_size=200),

112 batch_size=16)

113 # val_reader = paddle.reader(reador.reader_creator(X_val,Y_val),batch_size=16)

114

115 trainer.train(reader=train_reader,num_passes=20,event_handler=event_handler)

输出结果

上一步训练完以后，保存训练完的模型，然后写一个test.py进行预测，需要注意的是，在预测时，构建的网络结构得和训练的网络结构相同。

#批量预测测试图片准确率

python test.py /Users/shelter/test

##输出结果示例

output:

预测车牌号码为:津 K 4 2 R M Y

输入图片数量:100

输入图片行准确率:0.72

输入图片列准确率:0.86

如果是一次性只预测一张的话，在终端里会显示原始的图片与预测的值，如果是批量预测的话，会打印出预测的总准确率，包括行与列的准确率。

总结

车牌识别的方法有很多，商业化落地的方法也很成熟，传统的方法需要对图片灰度化，字符进行切分等，需要很多数据预处理的过程，端到端的方法可以直接将原始的图片灌进去进行训练，最后出来预测的车牌字符的结果，这个方法在构建了两层卷积-池化网络结构后，并行训练了7个全连接层来进行车牌的字符识别，可以实现端到端的识别。但是在实际训练过程中，仍然有一些问题，譬如前几个训练的全连接层的准确率要比最后一两个的准确率高，大家可以分别打印出每一个全连接层的训练结果准确率对比一下，可能是由于训练还没有收敛导致的，也可能有其他原因，如果在做的过程中发现有什么问题，或者有更好的方法，欢迎留言~

参考文献：

1.我的github：https://github.com/huxiaoman7/mxnet-cnn-plate-recognition

作者：Charlotte77