DCGAN，即深度卷积生成对抗网络（Deep Convolutional Generative Adversarial Network），是一种深度学习模型，由Ian Goodfellow等人在2014年提出。DCGAN在生成对抗网络（GAN）的基础上，引入了深度卷积神经网络（CNN）的结构，用于生成高质量、高分辨率的图像。

DCGAN的原理可以概括为两个主要部分：生成器（Generator）和判别器（Discriminator）。生成器和判别器都是深度卷积神经网络，它们通过对抗过程互相博弈，最终达到纳什均衡。

1. 生成器（Generator）：生成器的输入是一个随机的噪声向量，通过一系列的卷积、反卷积、批标准化（Batch Normalization）和激活函数（如ReLU、Tanh等）操作，生成一个与真实图像具有相同尺寸的图像。生成器的目标是生成尽可能逼真的图像，以欺骗判别器。

2. 判别器（Discriminator）：判别器的输入是一个图像，它通过一系列的卷积、批标准化和激活函数操作，判断输入图像是真实图像还是生成器生成的假图像。判别器的目标是能够准确地区分真实图像和假图像。

在训练过程中，生成器和判别器交替进行优化。生成器尝试生成逼真的图像，而判别器尝试更好地识别真实图像和假图像。这个过程可以看作是一种博弈，生成器和判别器在不断的迭代过程中提高自己的性能。最终，当生成器和判别器达到纳什均衡时，生成器能够生成高质量的逼真图像，判别器无法准确地区分真实图像和假图像。

DCGAN在计算机视觉领域有广泛的应用，如图像生成、图像修复、图像转换等。通过调整网络结构和训练策略，DCGAN还可以应用于其他领域，如自然语言处理、音频生成等。

数据准备与处理

%%capture captured_output
# 实验环境已经预装了mindspore==2.2.14，如需更换mindspore版本，可更改下面mindspore的版本号
!pip uninstall mindspore -y
!pip install -i https://pypi.mirrors.ustc.edu.cn/simple mindspore==2.2.14
from download import downloadurl = "https://download.mindspore.cn/dataset/Faces/faces.zip"path = download(url, "./faces", kind="zip", replace=True)
import numpy as np
import mindspore.dataset as ds
import mindspore.dataset.vision as visiondef create_dataset_imagenet(dataset_path):"""数据加载"""dataset = ds.ImageFolderDataset(dataset_path,num_parallel_workers=4,shuffle=True,decode=True)# 数据增强操作transforms = [vision.Resize(image_size),vision.CenterCrop(image_size),vision.HWC2CHW(),lambda x: ((x / 255).astype("float32"))]# 数据映射操作dataset = dataset.project('image')dataset = dataset.map(transforms, 'image')# 批量操作dataset = dataset.batch(batch_size)return datasetdataset = create_dataset_imagenet('./faces')
import matplotlib.pyplot as pltdef plot_data(data):# 可视化部分训练数据plt.figure(figsize=(10, 3), dpi=140)for i, image in enumerate(data[0][:30], 1):plt.subplot(3, 10, i)plt.axis("off")plt.imshow(image.transpose(1, 2, 0))plt.show()sample_data = next(dataset.create_tuple_iterator(output_numpy=True))
plot_data(sample_data)

构造网络

生成器

import mindspore as ms
from mindspore import nn, ops
from mindspore.common.initializer import Normalweight_init = Normal(mean=0, sigma=0.02)
gamma_init = Normal(mean=1, sigma=0.02)class Generator(nn.Cell):"""DCGAN网络生成器"""def __init__(self):super(Generator, self).__init__()self.generator = nn.SequentialCell(nn.Conv2dTranspose(nz, ngf * 8, 4, 1, 'valid', weight_init=weight_init),nn.BatchNorm2d(ngf * 8, gamma_init=gamma_init),nn.ReLU(),nn.Conv2dTranspose(ngf * 8, ngf * 4, 4, 2, 'pad', 1, weight_init=weight_init),nn.BatchNorm2d(ngf * 4, gamma_init=gamma_init),nn.ReLU(),nn.Conv2dTranspose(ngf * 4, ngf * 2, 4, 2, 'pad', 1, weight_init=weight_init),nn.BatchNorm2d(ngf * 2, gamma_init=gamma_init),nn.ReLU(),nn.Conv2dTranspose(ngf * 2, ngf, 4, 2, 'pad', 1, weight_init=weight_init),nn.BatchNorm2d(ngf, gamma_init=gamma_init),nn.ReLU(),nn.Conv2dTranspose(ngf, nc, 4, 2, 'pad', 1, weight_init=weight_init),nn.Tanh())def construct(self, x):return self.generator(x)generator = Generator()

判别器

class Discriminator(nn.Cell):"""DCGAN网络判别器"""def __init__(self):super(Discriminator, self).__init__()self.discriminator = nn.SequentialCell(nn.Conv2d(nc, ndf, 4, 2, 'pad', 1, weight_init=weight_init),nn.LeakyReLU(0.2),nn.Conv2d(ndf, ndf * 2, 4, 2, 'pad', 1, weight_init=weight_init),nn.BatchNorm2d(ngf * 2, gamma_init=gamma_init),nn.LeakyReLU(0.2),nn.Conv2d(ndf * 2, ndf * 4, 4, 2, 'pad', 1, weight_init=weight_init),nn.BatchNorm2d(ngf * 4, gamma_init=gamma_init),nn.LeakyReLU(0.2),nn.Conv2d(ndf * 4, ndf * 8, 4, 2, 'pad', 1, weight_init=weight_init),nn.BatchNorm2d(ngf * 8, gamma_init=gamma_init),nn.LeakyReLU(0.2),nn.Conv2d(ndf * 8, 1, 4, 1, 'valid', weight_init=weight_init),)self.adv_layer = nn.Sigmoid()def construct(self, x):out = self.discriminator(x)out = out.reshape(out.shape[0], -1)return self.adv_layer(out)discriminator = Discriminator()

模型训练

损失函数

# 定义损失函数
adversarial_loss = nn.BCELoss(reduction='mean')

优化器

# 为生成器和判别器设置优化器
optimizer_D = nn.Adam(discriminator.trainable_params(), learning_rate=lr, beta1=beta1)
optimizer_G = nn.Adam(generator.trainable_params(), learning_rate=lr, beta1=beta1)
optimizer_G.update_parameters_name('optim_g.')
optimizer_D.update_parameters_name('optim_d.')

训练模型

训练分为两个主要部分：训练判别器和训练生成器。

def generator_forward(real_imgs, valid):# 将噪声采样为发生器的输入z = ops.standard_normal((real_imgs.shape[0], nz, 1, 1))# 生成一批图像gen_imgs = generator(z)# 损失衡量发生器绕过判别器的能力g_loss = adversarial_loss(discriminator(gen_imgs), valid)return g_loss, gen_imgsdef discriminator_forward(real_imgs, gen_imgs, valid, fake):# 衡量鉴别器从生成的样本中对真实样本进行分类的能力real_loss = adversarial_loss(discriminator(real_imgs), valid)fake_loss = adversarial_loss(discriminator(gen_imgs), fake)d_loss = (real_loss + fake_loss) / 2return d_lossgrad_generator_fn = ms.value_and_grad(generator_forward, None,optimizer_G.parameters,has_aux=True)
grad_discriminator_fn = ms.value_and_grad(discriminator_forward, None,optimizer_D.parameters)@ms.jit
def train_step(imgs):valid = ops.ones((imgs.shape[0], 1), mindspore.float32)fake = ops.zeros((imgs.shape[0], 1), mindspore.float32)(g_loss, gen_imgs), g_grads = grad_generator_fn(imgs, valid)optimizer_G(g_grads)d_loss, d_grads = grad_discriminator_fn(imgs, gen_imgs, valid, fake)optimizer_D(d_grads)return g_loss, d_loss, gen_imgs
import mindsporeG_losses = []
D_losses = []
image_list = []total = dataset.get_dataset_size()
for epoch in range(num_epochs):generator.set_train()discriminator.set_train()# 为每轮训练读入数据for i, (imgs, ) in enumerate(dataset.create_tuple_iterator()):g_loss, d_loss, gen_imgs = train_step(imgs)if i % 100 == 0 or i == total - 1:# 输出训练记录print('[%2d/%d][%3d/%d]   Loss_D:%7.4f  Loss_G:%7.4f' % (epoch + 1, num_epochs, i + 1, total, d_loss.asnumpy(), g_loss.asnumpy()))D_losses.append(d_loss.asnumpy())G_losses.append(g_loss.asnumpy())# 每个epoch结束后，使用生成器生成一组图片generator.set_train(False)fixed_noise = ops.standard_normal((batch_size, nz, 1, 1))img = generator(fixed_noise)image_list.append(img.transpose(0, 2, 3, 1).asnumpy())# 保存网络模型参数为ckpt文件mindspore.save_checkpoint(generator, "./generator.ckpt")mindspore.save_checkpoint(discriminator, "./discriminator.ckpt")
plt.figure(figsize=(10, 5))
plt.title("Generator and Discriminator Loss During Training")
plt.plot(G_losses, label="G", color='blue')
plt.plot(D_losses, label="D", color='orange')
plt.xlabel("iterations")
plt.ylabel("Loss")
plt.legend()
plt.show()import matplotlib.pyplot as plt
import matplotlib.animation as animationdef showGif(image_list):show_list = []fig = plt.figure(figsize=(8, 3), dpi=120)for epoch in range(len(image_list)):images = []for i in range(3):row = np.concatenate((image_list[epoch][i * 8:(i + 1) * 8]), axis=1)images.append(row)img = np.clip(np.concatenate((images[:]), axis=0), 0, 1)plt.axis("off")show_list.append([plt.imshow(img)])ani = animation.ArtistAnimation(fig, show_list, interval=1000, repeat_delay=1000, blit=True)ani.save('./dcgan.gif', writer='pillow', fps=1)showGif(image_list)