卷积神经网络CNN相关模型python案例（LeNet-5、Inception_v3）

谁借莪１个温暖的怀抱￠ 2023-06-22 13:46 133阅读 0赞

### 一、卷积神经网络CNN ###

卷积神经网络是通过卷积层(convolutions)和池化层(pooling)将特征从多个的通道(channel)生成Feature Map，再通过全连接网络（full connections）得到最终输出的一种神经网络结构。  
卷积神经网络的结构通常如下：  
 输 入 − > ( 卷 积 层 c o n v o l u t i o n × N + 采 样 层 p o o l i n g ) × M − > 全 连 接 层 F C × K \\mathrm\{输入\}->(\\mathrm\{卷积层\}convolution\\times N+采样层pooling)\\times M->\\mathrm\{全连接层\}FC\\times K 输入−>(卷积层convolution×N\+采样层pooling)×M−>全连接层FC×K

**1. 卷积层（convolution）**  
一个卷积层是将深度为 d d d，每个深度上维度为 f × f f\\times f f×f的矩阵（过滤器/卷积核）按照卷积运算的方式，作用在深度（通道）为 d d d,且每个通道上为一个二维 m × n m\\times n m×n特征矩阵（Feature Map）上面，进行扫描运算。（还可以加上padding操作，防止矩阵越算算越小。）  
具体示意图如下：  
![在这里插入图片描述][aHR0cDovL3VwbG9hZC1pbWFnZXMuamlhbnNodS5pby91cGxvYWRfaW1hZ2VzLzIyNTY2NzItMTkxMTBkZWUwYzU0YzBiMi5naWY]  
卷积层可以看做将原有矩阵特征通过卷积核生成新矩阵特征的过程。

**2. 采样层（pooling）**  
Pooling层主要的作用是下采样，通过去掉Feature Map中不重要的样本，进一步减少参数数量。Pooling的方法很多，最常用的是Max Pooling。Max Pooling实际上就是在 n × n n\\times n n×n的样本中取最大值，作为采样后的样本值。Max Pooling的示意图如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70]  
pooling层的通常具有以下作用：  
对Feature Map进行压缩，保留主要的特征同时减少参数，提高模型泛华能力  
增加特征的平移不变性（矩阵进行平移后旋转等操作时，对卷积层的运算结果影响不大。（详细可参考[pooling的作用][pooling]）  
**3.全连接层（Full Connection）**  
将Feature Map展开成一维后，连接全连接层。

关于卷积神经网络，网上讲解非常多，此处不仔细表述，推荐一个关于神经网络很通俗易懂的教程：[零基础入门深度学习(4) - 卷积神经网络][4_ -]

### 二、LeNet-5的手写数字识别 ###

LeNet-5出自论文Gradient-Based Learning Applied to Document Recognition，对MNIST数据集（[mnist数据集下载地址][mnist]）的分识别准确度可达99.2%。其网络结构为：  
 输 入 − > ( 卷 积 层 c o n v o l u t i o n + 采 样 层 p o o l i n g ) × 2 − > 全 连 接 层 F C × 2 − > s o f t m a x 层 \\mathrm\{输入\}->(\\mathrm\{卷积层\}convolution+采样层pooling)\\times 2->\\mathrm\{全连接层\}FC\\times 2->softmax层 输入−>(卷积层convolution\+采样层pooling)×2−>全连接层FC×2−>softmax层

![LeNet-5结构示意图][LeNet-5]  
使用深度学习工具tensorflow，编写LeNet-5结构，并对mnist手写数字集（[mnist数据集下载地址][mnist]）进行训练。其模型训练的python代码如下：

# -*- coding: utf-8 -*-
    """
    Created on Tue Aug 20 17:51:50 2019
    @author: nbszg
    """
    
    #引入依赖包
    import os
    import struct
    import numpy as np
    import tensorflow as tf
    import matplotlib.pyplot as plt
    
    #数据加载函数
    def load_mnist(path, kind='train'):
        """load mnist date
        Args:
            path: date path
            kind: train or test
        Returns:
            images and labels
        """
        labels_path = os.path.join(path,'%s-labels.idx1-ubyte'% kind)   #标签数据
        images_path = os.path.join(path,'%s-images.idx3-ubyte'% kind)   #图像数据
        with open(labels_path, 'rb') as lbpath:
            magic, n = struct.unpack('>II',lbpath.read(8))
            labels = np.fromfile(lbpath,dtype=np.uint8)
        
        with open(images_path, 'rb') as imgpath:
            magic, num, rows, cols = struct.unpack('>IIII',imgpath.read(16))
            images = np.fromfile(imgpath,dtype=np.uint8).reshape(len(labels), 784)
            
        return images, labels
    
    
    path = 'D:/data/mnist/'   #数据所在路径
    X_train, y_train = load_mnist(path, kind='train')    #训练集
    X_test, y_test = load_mnist(path, kind='t10k')       #测试集
    
    #将label进行one-hot处理
    def y_onehot(y):
        """one-hot option
        Args:
            y: labels
        Returns:
            one-hot label
            eg:1->[0,1,0,0,0,0,0,0,0]
        """
        n_class = 10
        y_labels = np.eye(n_class)[y]
        return y_labels
    
    y_train_labels = y_onehot(y_train)
    y_test_labels = y_onehot(y_test)
    
    
    #网络权重变量
    def weight_variable(shape):
        """weight_variable
        Args:
            shape: weight's shape with 4 dimensions
        """
        initial = tf.truncated_normal(shape, stddev=0.1)   #对变量进行初始化
        return tf.Variable(initial)
    
    #网络偏置项变量
    def bias_variable(shape):
        """bias_variable
        Args:
            shape: bias's shape with 1 dimension
        """
        initial = tf.constant(0.1, shape=shape)
        return tf.Variable(initial)
    
    #定义卷积层，padding='SAME'
    def conv2d(x, W):
        """conv2d layer
        Args:
            x: input
            W:weights
        Returns:
            conv2d output
        """
        return tf.nn.conv2d(x, W, strides=[1, 1, 1, 1], padding='SAME')
    #定义pooling层，采用max_pooling
    def max_pool_2x2(x):
        """max pooling layer
        Args:
            x: input
        Returns:
            max pooling output
        """
        return tf.nn.max_pool(x, ksize=[1, 2, 2, 1],strides=[1, 2, 2, 1], padding='SAME')
    
    #超参
    learning_rate = 0.0001    #学习速率
    training_steps = 2000     #训练轮数
    batch_size = 200          #批训练大小
    display_step = 100        #展示步长
    
    X = tf.placeholder(tf.float32,[None, 784])      #训练X
    Y = tf.placeholder(tf.float32, [None, 10])      #标签y
    W_conv1 = weight_variable([5, 5, 1, 32])   #第一层卷积参数5*5，输入通道1，输出通道32
    b_conv1 = bias_variable([32])  #第一层卷积，偏置项输出通道32
    W_conv2 = weight_variable([5, 5, 32, 64]) #第二层卷积参数5*5，输入通道32，输出通道64
    b_conv2 = bias_variable([64])  #第二层卷积，偏置项输出通道64
    W_fc1 = weight_variable([7 * 7 * 64, 1024])  #全连接层，64个通道图像变为1维，为7*7*64；设置1024个神经元
    b_fc1 = bias_variable([1024]) #对应1024个偏置项
    keep_prob = tf.placeholder("float")     #drop_out概率
    W_fc2 = weight_variable([1024, 10])     #全连接层变量
    b_fc2 = bias_variable([10])             #全连接层偏置项
    
    def conv_net(x, W_conv1, b_conv1, W_conv2, b_conv2, W_fc1, b_fc1, W_fc2, b_fc2, keep_prob):
        """conv_net model
        Args:
            ...
        Returns:
            conv_net model prediction
        """
        x_image = tf.reshape(x, [-1,28,28,1])
        h_conv1 = tf.nn.relu(conv2d(x_image, W_conv1) + b_conv1)  #第一层卷积层：relu函数
        h_pool1 = max_pool_2x2(h_conv1)  #第一Pooling层，因为pooling步长为2，因此图像矩阵变为14*14
        h_conv2 = tf.nn.relu(conv2d(h_pool1, W_conv2) + b_conv2)  #第二层卷积层：relu函数，因为pooling步长为2
        h_pool2 = max_pool_2x2(h_conv2) #第二Pooling层，因为pooling步长为2，因此图像矩阵变为7*7
        h_pool2_flat = tf.reshape(h_pool2, [-1, 7*7*64])  #改变最后Plooing层形状，为对应的7*7*64
        h_fc1 = tf.nn.relu(tf.matmul(h_pool2_flat, W_fc1) + b_fc1)   #全连接层
        h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)
        y_conv=tf.nn.softmax(tf.matmul(h_fc1_drop, W_fc2) + b_fc2)   #最后softmax全连接层
        
        return y_conv
    
    y_conv = conv_net(X, W_conv1, b_conv1, W_conv2, b_conv2, W_fc1, b_fc1, W_fc2, b_fc2, keep_prob)
    
    cross_entropy = -tf.reduce_mean(Y*tf.log(tf.clip_by_value(y_conv,1e-11,1.0)))   #交叉熵为目标函数
    train_step = tf.train.AdamOptimizer(learning_rate).minimize(cross_entropy)    #Adam梯度下降优化
    correct_prediction = tf.equal(tf.argmax(y_conv,1), tf.argmax(Y,1))   #判断预测准确率
    accuracy = tf.reduce_mean(tf.cast(correct_prediction, "float"))     #准确率
    
    init = tf.global_variables_initializer()
    
    #定义模型载入函数
    def load_model(sess, saver,ckpt_path):
        latest_ckpt = tf.train.latest_checkpoint(ckpt_path)
        if latest_ckpt:    #如果之间训练过，可以在训练过的模型的基础上继续进行训练
            print ('resume from', latest_ckpt)
            saver.restore(sess, latest_ckpt)   
            return int(latest_ckpt[latest_ckpt.rindex('-') + 1:])
        else:
            print ('building model start')
            sess.run(tf.global_variables_initializer())
            return -1
            
    #模型训练
    with tf.Session() as sess:
        sess.run(init)
        total_batch = int(len(X_train)/batch_size)
        
        saver = tf.train.Saver(tf.global_variables())
        last_epoch = load_model(sess, saver,'D:/data/mnist/cnn_model_file/')
        
        for step in range(1,training_steps+1):
            for i in range(1,total_batch):
                batch_x = X_train[(i-1)*batch_size: i*batch_size]
                batch_y = y_train_labels[(i-1)*batch_size: i*batch_size]
                
                sess.run(train_step, feed_dict={
        X:batch_x, Y:batch_y, keep_prob: 0.5})
    
            if (step) % display_step == 0:
                
                loss,acc = sess.run([cross_entropy,accuracy], feed_dict={
        X:X_train[0:1000], Y:y_train_labels[0:1000], keep_prob: 1.0})
                print ("Step"+str(step)+", Minibatch Loss=========>"+"{:.4f}".format(loss)+", Training Accuracy=========>"+"{:.3f}".format(acc))
    
            saver.save(sess, 'D:/data/mnist/cnn_mnist.module', global_step=step)
            
        loss, acc = sess.run([cross_entropy, accuracy], feed_dict={
        X:X_train[0:1000], Y:y_train_labels[0:1000], keep_prob: 1.0})
        print ("Step"+str(step)+", Minibatch Loss="+"{:.4f}".format(loss)+", Training Accuracy="+"{:.3f}".format(acc))
        
        print ("Optimization Finished!")

使用训练好的模型对test集的样本进行预测。次数列举对10张图片的预测结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70 1]  
可以看到，LeNet对10张手写数字图片的预测都是正确的。

### 二、Inception-V3的猫狗图片分类 ###

Inception 网络是 CNN 分类器发展史上一个重要的里程碑。之前的CNN总是尝试卷积层的不断传串联，希望用越来越深的网络达到更好的效果。而Inception族的网络是网络不在是简单的堆叠加深。Inception-V3便是Inception其中的一员。其网络结构如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70 2]  
关于Inception-V3的更多知识可阅读：[深度学习卷积神经网络——经典网络GoogLeNet(Inception V3)网络的搭建与实现][GoogLeNet_Inception V3]

Keras 是一个用 Python 编写的高级神经网络 API，它能够以 TensorFlow, CNTK, 或者 Theano 作为后端运行。当以TensorFlow为后端时，Kreas可以看做TensorFlow的封装。此时Kreas的编写往往比TensorFlow编写更加简单。因此此处使用Kreas对Inception-V3案例进行编写。

Inception-V3结构大约有2500万个参数，使用普通个人电脑对其进行训练是本可能完成的。因此此处使用迁移学习，将已经训练好的Inception-V3的大部分层参数直接载入，只对最后几层的网络进行训练。

模型训练的python代码如下：

# -*- coding: utf-8 -*-
    """
    Created on Tue Aug 21 13:31:50 2019
    @author: nbszg
    """
    
    #引入依赖包# -*- coding: utf-8 -*-
    import os
    import numpy as np
    from keras.applications.inception_v3 import InceptionV3
    from keras.layers import Dense,Flatten,GlobalAveragePooling2D
    from keras.models import Model,load_model
    from keras.optimizers import SGD
    from keras.preprocessing.image import ImageDataGenerator
    import matplotlib.pyplot as plt
    
    import warnings
    warnings.filterwarnings('ignore')
    
    class PowerTransferMode:
        #数据准备
        def DataGen(self, dir_path, img_row, img_col, batch_size, is_train):
            
            """
            data enhancement
            Args:
                dir_path:dir path of data
                img_row: image width
                img_col: image height
                batch_size: bitch_size of trian
                is_train: boolean
            return：
                data enhancement result
            """
            #数据增强可以增加训练数据，包括平移，旋转，镜像，加入噪声等
            if is_train:
                datagen = ImageDataGenerator(rescale=1./255,
                    zoom_range=0.25, rotation_range=15.,
                    channel_shift_range=25., width_shift_range=0.02, height_shift_range=0.02,
                    horizontal_flip=True, fill_mode='constant')
            else:
                datagen = ImageDataGenerator(rescale=1./255)    #若不是训练集，则直接输出
    
            generator = datagen.flow_from_directory(
                dir_path, target_size=(img_row, img_col),
                batch_size=batch_size,
                #class_mode='binary',
                shuffle=is_train)
    
            return generator
    
        # InceptionV3模型
        def InceptionV3_model(self, lr=0.005, decay=1e-6, momentum=0.9, nb_classes=2, img_rows=197, img_cols=197, RGB=True):
            """
            InceptionV3_model
            Args:
                ...
            return：
                InceptionV3_model
            """
            color = 3 if RGB else 1
            base_model = InceptionV3(weights='imagenet', include_top=False, pooling=None,input_shape=(img_rows, img_cols, color),classes=nb_classes)         #迁移学习，InceptionV3_model模型复用
    
            # 冻结base_model所有层，这样就可以正确获得bottleneck特征
            for layer in base_model.layers:
                layer.trainable = False    #迁移学习的InceptionV3_model部分不需要再训练
    
            x = base_model.output
            # 添加自己的全链接分类层
            x = GlobalAveragePooling2D()(x)       #添加average pooling层
            x = Dense(1024, activation='relu')(x)    #全连接层
            predictions = Dense(nb_classes, activation='softmax')(x)    #softmax输出预测结果
    
            # 训练模型
            model = Model(inputs=base_model.input, outputs=predictions)
            sgd = SGD(lr=lr, decay=decay, momentum=momentum, nesterov=True)    #优化器
            model.compile(loss='categorical_crossentropy', optimizer=sgd, metrics=['accuracy'])
    
    
            return model
        
        #训练模型
        def train_model(self, model, epochs, train_generator, steps_per_epoch, validation_generator, 
                        validation_steps, model_url, is_load_model=False):  
            """
            train model
            Args:
                ...
            return：
                model trained
            """
            if is_load_model and os.path.exists(model_url):
                model = load_model(model_url)    #载入模型
                
            history_ft = model.fit_generator(
                train_generator,
                steps_per_epoch=steps_per_epoch,
                epochs=epochs,
                validation_data=validation_generator,
                validation_steps=validation_steps)     #模型训练
            model.save(model_url,overwrite=True)     #模型保存
            return history_ft
    
    
    image_size = 197
    batch_size = 32
    transfer = PowerTransferMode()
    train_generator = transfer.DataGen('D:/data/cat_vs_dog/train_set/', image_size, image_size, batch_size, True)
    validation_generator = transfer.DataGen('D:/data/cat_vs_dog/validation_set/', image_size, image_size, batch_size, False)
    model = transfer.InceptionV3_model(nb_classes=2, img_rows=image_size, img_cols=image_size, is_plot_model=False)
    history_ft = transfer.train_model(model, 10, train_generator, 600, validation_generator, 60, 'D:/data/cat_vs_dog/inceptionv3_nbs.model', is_load_model=False)   #'D:/data/cat_vs_dog/inceptionv3_nbs.model'为已经下载好的迁移学习预训练文件

使用训练好的模型对t10张猫狗图片进行预测，预测结果如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70 3]

[aHR0cDovL3VwbG9hZC1pbWFnZXMuamlhbnNodS5pby91cGxvYWRfaW1hZ2VzLzIyNTY2NzItMTkxMTBkZWUwYzU0YzBiMi5naWY]: https://imgconvert.csdnimg.cn/aHR0cDovL3VwbG9hZC1pbWFnZXMuamlhbnNodS5pby91cGxvYWRfaW1hZ2VzLzIyNTY2NzItMTkxMTBkZWUwYzU0YzBiMi5naWY
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191216163719545.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI=,size_16,color_FFFFFF,t_70
[pooling]: https://blog.csdn.net/kele_imon/article/details/79532286
[4_ -]: https://www.zybuluo.com/hanbingtao/note/485480
[mnist]: http://yann.lecun.com/exdb/mnist/
[LeNet-5]: https://img-blog.csdnimg.cn/2019121616523634.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20191216171411344.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/201912161735491.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI=,size_16,color_FFFFFF,t_70
[GoogLeNet_Inception V3]: https://blog.csdn.net/loveliuzz/article/details/79135583
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/2019121617523550.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1MTcxMzI=,size_16,color_FFFFFF,t_70