卷积神经网络（CNN）多种图片分类的实现

前期工作

1. 设置GPU（如果使用的是CPU可以忽略这步）

我的环境：

• 语言环境：Python3.6.5
• 编译器：jupyter notebook
• 深度学习环境：TensorFlow2.4.1

import tensorflow as tf
gpus = tf.config.list_physical_devices("GPU")

if gpus:
    gpu0 = gpus[0] #如果有多个GPU，仅使用第0个GPU
    tf.config.experimental.set_memory_growth(gpu0, True) #设置GPU显存用量按需使用
    tf.config.set_visible_devices([gpu0],"GPU")

2. 导入数据

import tensorflow as tf
from tensorflow.keras import datasets, layers, models
import matplotlib.pyplot as plt

(train_images, train_labels), (test_images, test_labels) = datasets.cifar10.load_data()

3.归一化

# 将像素的值标准化至0到1的区间内。
train_images, test_images = train_images / 255.0, test_images / 255.0

train_images.shape,test_images.shape,train_labels.shape,test_labels.shape

4.可视化

class_names = ['airplane', 'automobile', 'bird', 'cat', 'deer','dog', 'frog', 'horse', 'ship', 'truck']

plt.figure(figsize=(20,10))
for i in range(20):
    plt.subplot(5,10,i+1)
    plt.xticks([])
    plt.yticks([])
    plt.grid(False)
    plt.imshow(train_images[i], cmap=plt.cm.binary)
    plt.xlabel(class_names[train_labels[i][0]])
plt.show()

二、构建CNN网络模型

model = models.Sequential([
    layers.Conv2D(32, (3, 3), activation='relu', input_shape=(32, 32, 3)), #卷积层1，卷积核3*3
    layers.MaxPooling2D((2, 2)),                   #池化层1，2*2采样
    layers.Conv2D(64, (3, 3), activation='relu'),  #卷积层2，卷积核3*3
    layers.MaxPooling2D((2, 2)),                   #池化层2，2*2采样
    layers.Conv2D(64, (3, 3), activation='relu'),  #卷积层3，卷积核3*3
    
    layers.Flatten(),                      #Flatten层，连接卷积层与全连接层
    layers.Dense(64, activation='relu'),   #全连接层，特征进一步提取
    layers.Dense(10)                       #输出层，输出预期结果
])

model.summary()  # 打印网络结构

Model: "sequential"
_________________________________________________________________
Layer (type)                 Output Shape              Param #   
=================================================================
conv2d (Conv2D)              (None, 30, 30, 32)        896       
_________________________________________________________________
max_pooling2d (MaxPooling2D) (None, 15, 15, 32)        0         
_________________________________________________________________
conv2d_1 (Conv2D)            (None, 13, 13, 64)        18496     
_________________________________________________________________
max_pooling2d_1 (MaxPooling2 (None, 6, 6, 64)          0         
_________________________________________________________________
conv2d_2 (Conv2D)            (None, 4, 4, 64)          36928     
_________________________________________________________________
flatten (Flatten)            (None, 1024)              0         
_________________________________________________________________
dense (Dense)                (None, 64)                65600     
_________________________________________________________________
dense_1 (Dense)              (None, 10)                650       
=================================================================
Total params: 122,570
Trainable params: 122,570
Non-trainable params: 0
_________________________________________________________________

三、编译模型

model.compile(optimizer='adam',
              loss=tf.keras.losses.SparseCategoricalCrossentropy(from_logits=True),
              metrics=['accuracy'])

四、训练模型

history = model.fit(train_images, train_labels, epochs=10, 
                    validation_data=(test_images, test_labels))

Epoch 1/10
1563/1563 [==============================] - 9s 4ms/step - loss: 1.7862 - accuracy: 0.3390 - val_loss: 1.2697 - val_accuracy: 0.5406
Epoch 2/10
1563/1563 [==============================] - 5s 3ms/step - loss: 1.2270 - accuracy: 0.5595 - val_loss: 1.0731 - val_accuracy: 0.6167
Epoch 3/10
1563/1563 [==============================] - 5s 3ms/step - loss: 1.0355 - accuracy: 0.6337 - val_loss: 0.9678 - val_accuracy: 0.6610
Epoch 4/10
1563/1563 [==============================] - 5s 3ms/step - loss: 0.9221 - accuracy: 0.6727 - val_loss: 0.9589 - val_accuracy: 0.6648
Epoch 5/10
1563/1563 [==============================] - 5s 3ms/step - loss: 0.8474 - accuracy: 0.7022 - val_loss: 0.8962 - val_accuracy: 0.6853
Epoch 6/10
1563/1563 [==============================] - 5s 3ms/step - loss: 0.7814 - accuracy: 0.7292 - val_loss: 0.9124 - val_accuracy: 0.6873
Epoch 7/10
1563/1563 [==============================] - 5s 3ms/step - loss: 0.7398 - accuracy: 0.7398 - val_loss: 0.8924 - val_accuracy: 0.6929
Epoch 8/10
1563/1563 [==============================] - 5s 3ms/step - loss: 0.7008 - accuracy: 0.7542 - val_loss: 0.9809 - val_accuracy: 0.6854
Epoch 9/10
1563/1563 [==============================] - 5s 3ms/step - loss: 0.6474 - accuracy: 0.7732 - val_loss: 0.8549 - val_accuracy: 0.7137
Epoch 10/10
1563/1563 [==============================] - 5s 3ms/step - loss: 0.6041 - accuracy: 0.7889 - val_loss: 0.8909 - val_accuracy: 0.7046

五、预测

通过模型进行预测得到的是每一个类别的概率，数字越大该图片为该类别的可能性越大

plt.imshow(test_images[10])

输出测试集中第一张图片的预测结果

import numpy as np

pre = model.predict(test_images)
print(class_names[np.argmax(pre[10])])

313/313 [==============================] - 1s 3ms/step
airplane

六、模型评估

import matplotlib.pyplot as plt

plt.plot(history.history['accuracy'], label='accuracy')
plt.plot(history.history['val_accuracy'], label = 'val_accuracy')
plt.xlabel('Epoch')
plt.ylabel('Accuracy')
plt.ylim([0.5, 1])
plt.legend(loc='lower right')
plt.show()

test_loss, test_acc = model.evaluate(test_images,  test_labels, verbose=2)

print(test_acc)

0.7166000008583069