Keras实现对抗自编码器模型生成MNIST数字图像

#头条创作挑战赛#

当使用Keras实现Adversarial Autoencoder（对抗自编码器）模型生成MNIST数字图像时，需要按照以下步骤进行操作。

首先，导入所需的库和模块：

from keras.layers import Input, Dense, Reshape, Flatten, Dropout
from keras.layers import BatchNormalization, Activation, ZeroPadding2D
from keras.layers.advanced_activations import LeakyReLU
from keras.layers.convolutional import UpSampling2D, Conv2D
from keras.models import Sequential, Model
from keras.optimizers import Adam
from keras.datasets import mnist
import matplotlib.pyplot as plt
import numpy as np

接下来，定义生成器模型和判别器模型：

def build_generator():

    model = Sequential()

    model.add(Dense(256, input_dim=100))
    model.add(LeakyReLU(alpha=0.2))
    model.add(BatchNormalization(momentum=0.8))
    model.add(Dense(512))
    model.add(LeakyReLU(alpha=0.2))
    model.add(BatchNormalization(momentum=0.8))
    model.add(Dense(1024))
    model.add(LeakyReLU(alpha=0.2))
    model.add(BatchNormalization(momentum=0.8))
    model.add(Dense(np.prod((28, 28, 1)), activation='tanh'))
    model.add(Reshape((28, 28, 1)))

    model.summary()

    noise = Input(shape=(100,))
    img = model(noise)

    return Model(noise, img)


def build_discriminator():

    model = Sequential()

    model.add(Flatten(input_shape=(28, 28, 1)))
    model.add(Dense(512))
    model.add(LeakyReLU(alpha=0.2))
    model.add(Dense(256))
    model.add(LeakyReLU(alpha=0.2))
    model.add(Dense(1, activation='sigmoid'))

    model.summary()

    img = Input(shape=(28, 28, 1))
    validity = model(img)

    return Model(img, validity)

然后，定义Adversarial Autoencoder模型：

def build_adversarial_autoencoder(generator, discriminator):

    discriminator.trainable = False

    autoencoder = Sequential()
    autoencoder.add(generator)
    autoencoder.add(discriminator)

    return autoencoder

接下来，加载MNIST数据集并进行预处理：

(X_train, _), (_, _) = mnist.load_data()

X_train = X_train / 127.5 - 1.
X_train = np.expand_dims(X_train, axis=3)

定义一些超参数：

epochs = 20000
batch_size = 32

sample_interval = 1000

然后，编译生成器、判别器和Adversarial Autoencoder模型：

generator = build_generator()
discriminator = build_discriminator()
adversarial_autoencoder = build_adversarial_autoencoder(generator, discriminator)

discriminator.compile(loss='binary_crossentropy', optimizer=Adam(0.0002, 0.5))
adversarial_autoencoder.compile(loss='binary_crossentropy', optimizer=Adam(0.0002, 0.5))

接下来，定义训练过程：

for epoch in range(epochs):

    # ---------------------
    #  训练判别器
    # ---------------------

    # 从训练集中随机选择一批图像
    idx = np.random.randint(0, X_train.shape[0], batch_size)
    imgs = X_train[idx]

    # 生成一批噪声数据
    noise = np.random.normal(0, 1, (batch_size, 100))

    # 使用生成器生成一批假图像
    gen_imgs = generator.predict(noise)

    # 训练判别器
    d_loss_real = discriminator.train_on_batch(imgs, np.ones((batch_size, 1)))
    d_loss_fake = discriminator.train_on_batch(gen_imgs, np.zeros((batch_size, 1)))
    d_loss = 0.5 * np.add(d_loss_real, d_loss_fake)

    # ---------------------
    #  训练生成器
    # ---------------------

    # 生成一批噪声数据
    noise = np.random.normal(0, 1, (batch_size, 100))

    # 训练生成器
    g_loss = adversarial_autoencoder.train_on_batch(noise, np.ones((batch_size, 1)))

    # 打印损失值
    print("%d [D loss: %f] [G loss: %f]" % (epoch, d_loss, g_loss))

    # 每隔一段时间保存并输出生成的图像样本
    if epoch % sample_interval == 0:
        r, c = 5, 5
        noise = np.random.normal(0, 1, (r * c, 100))
        gen_imgs = generator.predict(noise)

        gen_imgs = 0.5 * gen_imgs + 0.5

        fig, axs = plt.subplots(r, c)
        cnt = 0
        for i in range(r):
            for j in range(c):
                axs[i, j].imshow(gen_imgs[cnt, :, :, 0], cmap='gray')
                axs[i, j].axis('off')
                cnt += 1
        plt.show()
        plt.close()

最后，运行训练过程：

build_adversarial_autoencoder(generator, discriminator)

这是一个简单的使用Keras实现Adversarial Autoencoder模型生成MNIST数字图像的示例。请注意，这只是一个基础的实现，您可以根据需要进行修改和改进。