# 将VGG16卷积基实例化
from keras.applications import VGG16

conv_base = VGG16(weights='imagenet',  # 模型初始化检查点
                  include_top=False,  # 指定模型最后是否包含密集连接分类器
                  input_shape=(150, 150, 3))  # 输入到网络中的图像张量的形状

print(conv_base.summary())


# 不使用数据增强的快速特征提取
import os
import numpy as np
from keras.preprocessing.image import ImageDataGenerator  # 导入ImageDataGenerator类

base_dir = 'D:/DeepLearning/kaggle/cats_and_dogs_small'
train_dir = os.path.join(base_dir, 'train')  # 路径拼接
validation_dir = os.path.join(base_dir, 'validation')
test_dir = os.path.join(base_dir, 'test')

# 使用数据增强的特征提取
from keras import models
from keras import layers

model = models.Sequential()
model.add(conv_base)
model.add(layers.Flatten())
model.add(layers.Dense(256, activation='relu'))
model.add(layers.Dense(1, activation='sigmoid'))

print (model.summary())
'''
conv_base.trainable = False  # 冻结卷积基
'''
# 冻结直到某一层的所有层
conv_base.trainable = True
set_trainable = False
for layer in conv_base.layers:
    if layer.name == 'block5_conv1':
        set_trainable = True
    if set_trainable:
        layer.trainable = True
    else:
        layer.trainable = False

# 利用冻结卷积基端到端地训练模型
from keras.preprocessing.image import ImageDataGenerator
from keras import optimizers

train_datagen = ImageDataGenerator(
    rescale=1./255,
    rotation_range=40,
    width_shift_range=0.2,
    height_shift_range=0.2,
    shear_range=0.2,
    zoom_range=0.2,
    horizontal_flip=True,
    fill_mode='nearest')

test_datagen = ImageDataGenerator(rescale=1./255)  # 注意，不能增强验证数据

train_generator = train_datagen.flow_from_directory(
    train_dir,
    target_size=(150, 150),
    batch_size=20,
    class_mode='binary')

validation_generator = test_datagen.flow_from_directory(
    validation_dir,
    target_size=(150, 150),
    batch_size=20,
    class_mode='binary')

# 微调模型
model.compile(loss='binary_crossentropy',
              optimizer=optimizers.RMSprop(lr=1e-5),
              metrics=['acc'])

history = model.fit_generator(
    train_generator,
    steps_per_epoch=100,
    epochs=100,
    validation_data=validation_generator,
    validation_steps=50)

# 绘制结果
import matplotlib.pyplot as plt

acc = history.history['acc']
val_acc = history.history['val_acc']
loss = history.history['loss']
val_loss = history.history['val_loss']

epochs = range(1, len(acc) + 1)

plt.plot(epochs, acc, 'bo', label='Training acc')
plt.plot(epochs, val_acc, 'b', label='Validation acc')
plt.title('Training and validation accuracy')
plt.legend()

plt.figure()

plt.plot(epochs, loss, 'bo', label='Training loss')
plt.plot(epochs, val_loss, 'b', label='Validation loss')
plt.title('Training and validation loss')
plt.legend()

plt.show()

微调模型的训练精度和验证精度.png

微调模型的训练损失和验证损失.png