Deep Convolutional Generative Adversarial Network – TensorFlow

This tutorial demonstrates how to generate images of handwritten digits using a Deep Convolutional Generative Adversarial Network (DCGAN). The code is written using the Keras Sequential API with a tf.GradientTape training loop.

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What are GANs?

Generative Adversarial Networks (GANs) are one of the most interesting ideas in computer science today. Two models are trained simultaneously by an adversarial process. A generator (“the artist”) learns to create images that look real, while a discriminator (“the art critic”) learns to tell real images apart from fakes.

During training, the generator progressively becomes better at creating images that look real, while the discriminator becomes better at telling them apart. The process reaches equilibrium when the discriminator can no longer distinguish real images from fakes.

This notebook demonstrates this process on the MNIST dataset. The following animation shows a series of images produced by the generator as it was trained for 50 epochs. The images begin as random noise, and increasingly resemble hand written digits over time.

To learn more about GANs, see MIT’s Intro to Deep Learning course.

cài đặt

import tensorflow as tf 2022-12-14 06:05:17.257809: W tensorflow/compiler/xla/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library ‘libnvinfer.so.7’; dlerror: libnvinfer.so.7: cannot open shared object file: No such file or directory 2022-12-14 06:05:17.257923: W tensorflow/compiler/xla/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library ‘libnvinfer_plugin.so.7’; dlerror: libnvinfer_plugin.so.7: cannot open shared object file: No such file or directory 2022-12-14 06:05:17.257933: W tensorflow/compiler/tf2tensorrt/utils/py_utils.cc:38] TF-TRT Warning: Cannot dlopen some TensorRT libraries. If you would like to use Nvidia GPU with TensorRT, please make sure the missing libraries mentioned above are installed properly. tf.__version__ ‘2.11.0’ # To generate GIFs pip install imageio pip install git+https://github.com/tensorflow/docs import glob import imageio import matplotlib.pyplot as plt import numpy as np import os import PIL from tensorflow.keras import layers import time from IPython import display

Load and prepare the dataset

You will use the MNIST dataset to train the generator and the discriminator. The generator will generate handwritten digits resembling the MNIST data.

(train_images, train_labels), (_, _) = tf.keras.datasets.mnist.load_data() train_images = train_images.reshape(train_images.shape[0], 28, 28, 1).astype(‘float32’) train_images = (train_images – 127.5) / 127.5 # Normalize the images to [-1, 1] BUFFER_SIZE = 60000 BATCH_SIZE = 256 # Batch and shuffle the data train_dataset = tf.data.Dataset.from_tensor_slices(train_images).shuffle(BUFFER_SIZE).batch(BATCH_SIZE)

Create the models

Both the generator and discriminator are defined using the Keras Sequential API.

The Generator

The generator uses tf.keras.layers.Conv2DTranspose (upsampling) layers to produce an image from a seed (random noise). Start with a Dense layer that takes this seed as input, then upsample several times until you reach the desired image size of 28x28x1. Notice the tf.keras.layers.LeakyReLU activation for each layer, except the output layer which uses tanh.

def make_generator_model(): model = tf.keras.Sequential() model.Địa chỉ cửa hàng(layers.Dense(7*7*256, use_bias=False, input_shape=(200,))) model.Địa chỉ cửa hàng(layers.BatchNormalization()) model.Địa Chỉ(layers.LeakyReLU()) model.Địa chỉ cửa hàng(layers.Reshape((7, 7, 256))) assert model.output_shape == (None, 7, 7, 256) # Note: None is the batch size model.Địa Chỉ(layers.Conv2DTranspose(128, (5, 5), strides=(1, 1), padding=’same’, use_bias=False)) assert model.output_shape == (None, 7, 7, 128) model.Địa Chỉ(layers.BatchNormalization()) model.Địa chỉ cửa hàng(layers.LeakyReLU()) model.Địa Chỉ(layers.Conv2DTranspose(64, (5, 5), strides=(2, 2), padding=’same’, use_bias=False)) assert model.output_shape == (None, 14, 14, 64) model.Địa chỉ cửa hàng(layers.BatchNormalization()) model.Địa Chỉ(layers.LeakyReLU()) model.Địa Chỉ(layers.Conv2DTranspose(1, (5, 5), strides=(2, 2), padding=’same’, use_bias=False, activation=’tanh’)) assert model.output_shape == (None, 28, 28, 1) return model

Use the (as yet untrained) generator to create an image.

generator = make_generator_model() noise = tf.random.normal([1, 400]) generated_image = generator(noise, training=False) plt.imshow(generated_image[0, :, :, 0], cmap=’gray’) <matplotlib.image.AxesImage at 0x7f0d6ec39af0>

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The Discriminator

The discriminator is a CNN-based image classifier.

def make_discriminator_model(): model = tf.keras.Sequential() model.Địa Chỉ(layers.Conv2D(64, (5, 5), strides=(2, 2), padding=’same’, input_shape=[28, 28, 1])) model.Địa Chỉ(layers.LeakyReLU()) model.Địa Chỉ(layers.Dropout(0.3)) model.Địa Chỉ(layers.Conv2D(128, (5, 5), strides=(2, 2), padding=’same’)) model.Địa Chỉ(layers.LeakyReLU()) model.Địa chỉ cửa hàng(layers.Dropout(0.3)) model.Địa Chỉ(layers.Flatten()) model.Địa Chỉ(layers.Dense(1)) return model

Use the (as yet untrained) discriminator to classify the generated images as real or fake. The model will be trained to output positive values for real images, and negative values for fake images.

discriminator = make_discriminator_model() decision = discriminator(generated_image) print (decision) tf.Tensor([[0.00142179]], shape=(1, 1), dtype=float32)

Define the loss and optimizers

Define loss functions and optimizers for both models.

# This method returns a helper function to compute cross entropy loss cross_entropy = tf.keras.losses.BinaryCrossentropy(from_logits=True)

Discriminator loss

This method quantifies how well the discriminator is able to distinguish real images from fakes. It compares the discriminator’s predictions on real images to an array of 1s, and the discriminator’s predictions on fake (generated) images to an array of 0s.

def discriminator_loss(real_output, fake_output): real_loss = cross_entropy(tf.ones_like(real_output), real_output) fake_loss = cross_entropy(tf.zeros_like(fake_output), fake_output) total_loss = real_loss + fake_loss return total_loss

Generator loss

The generator’s loss quantifies how well it was able to trick the discriminator. Intuitively, if the generator is performing well, the discriminator will classify the fake images as real (or 1). Here, compare the discriminators decisions on the generated images to an array of 1s.

def generator_loss(fake_output): return cross_entropy(tf.ones_like(fake_output), fake_output)

The discriminator and the generator optimizers are different since you will train two networks separately.

generator_optimizer = tf.keras.optimizers.Adam(1e-4) discriminator_optimizer = tf.keras.optimizers.Adam(1e-4)

Save checkpoints

This notebook also demonstrates how to save and restore models, which can be helpful in case a long running training task is interrupted.

checkpoint_dir = ‘./training_checkpoints’ checkpoint_prefix = os.path.join(checkpoint_dir, “ckpt”) checkpoint = tf.train.Checkpoint(generator_optimizer=generator_optimizer, discriminator_optimizer=discriminator_optimizer, generator=generator, discriminator=discriminator)

Define the training loop

EPOCHS = 50 noise_dim = 300 num_examples_to_generate = 16 # You will reuse this seed overtime (so it’s easier) # to visualize progress in the animated GIF) seed = tf.random.normal([num_examples_to_generate, noise_dim])

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The training loop begins with generator receiving a random seed as input. That seed is used to produce an image. The discriminator is then used to classify real images (drawn from the training set) and fakes images (produced by the generator). The loss is calculated for each of these models, and the gradients are used to cập nhật the generator and discriminator.

# Notice the use of `tf.function` # This annotation causes the function to be “compiled”. @tf.function def train_step(images): noise = tf.random.normal([BATCH_SIZE, noise_dim]) with tf.GradientTape() as gen_tape, tf.GradientTape() as disc_tape: generated_images = generator(noise, training=True) real_output = discriminator(images, training=True) fake_output = discriminator(generated_images, training=True) gen_loss = generator_loss(fake_output) disc_loss = discriminator_loss(real_output, fake_output) gradients_of_generator = gen_tape.gradient(gen_loss, generator.trainable_variables) gradients_of_discriminator = disc_tape.gradient(disc_loss, discriminator.trainable_variables) generator_optimizer.apply_gradients(zip(gradients_of_generator, generator.trainable_variables)) discriminator_optimizer.apply_gradients(zip(gradients_of_discriminator, discriminator.trainable_variables)) def train(dataset, epochs): for epoch in range(epochs): start = time.time() for image_batch in dataset: train_step(image_batch) # Produce images for the GIF as you go display.clear_output(wait=True) generate_and_save_images(generator, epoch + 1, seed) # Save the model every 15 epochs if (epoch + 1) % 15 == 0: checkpoint.save(file_prefix = checkpoint_prefix) print (‘Time for epoch {} is {} sec’.format(epoch + 1, time.time()-start)) # Generate after the final epoch display.clear_output(wait=True) generate_and_save_images(generator, epochs, seed)

Generate and save images

def generate_and_save_images(model, epoch, test_input): # Notice `training` is set to False. # This is so all layers run in inference mode (batchnorm). predictions = model(test_input, training=False) fig = plt.figure(figsize=(4, 4)) for i in range(predictions.shape[0]): plt.subplot(4, 4, i+1) plt.imshow(predictions[i, :, :, 0] * 127.5 + 127.5, cmap=’gray’) plt.axis(‘off’) plt.savefig(‘image_at_epoch_{:04d}.png’.format(epoch)) plt.show()

Train the model

Call the train() method defined above to train the generator and discriminator simultaneously. Note, training GANs can be tricky. It’s important that the generator and discriminator do not overpower each other (e.g., that they train at a similar rate).

At the beginning of the training, the generated images look like random noise. As training progresses, the generated digits will look increasingly real. After about 50 epochs, they resemble MNIST digits. This may take about one minute / epoch with the default settings on Colab.

train(train_dataset, EPOCHS)

Restore the latest checkpoint.

checkpoint.restore(tf.train.latest_checkpoint(checkpoint_dir)) <tensorflow.python.checkpoint.checkpoint.CheckpointLoadStatus at 0x7f0e38330fa0>

Create a GIF

# Display a single image using the epoch number def display_image(epoch_no): return PIL.Image.open(‘image_at_epoch_{:04d}.png’.format(epoch_no)) display_image(EPOCHS)

Use imageio to create an animated gif using the images saved during training.

anim_file = ‘dcgan.gif’ with imageio.get_writer(anim_file, mode=’I’) as writer: filenames = glob.glob(‘image*.png’) filenames = sorted(filenames) for filename in filenames: image = imageio.imread(filename) writer.append_data(image) image = imageio.imread(filename) writer.append_data(image) /tmpfs/tmp/ipykernel_201453/1982054950.py&colon;7&colon; DeprecationWarning&colon; Starting with ImageIO v3 the behavior of this function will switch to that of iio.v3.imread. To keep the current behavior (and make this warning disappear) use `import imageio.v2 as imageio` or call `imageio.v2.imread` directly. image = imageio.imread(filename) /tmpfs/tmp/ipykernel_201453/1982054950.py&colon;9&colon; DeprecationWarning&colon; Starting with ImageIO v3 the behavior of this function will switch to that of iio.v3.imread. To keep the current behavior (and make this warning disappear) use `import imageio.v2 as imageio` or call `imageio.v2.imread` directly. image = imageio.imread(filename) import tensorflow_docs.vis.embed as embed embed.embed_file(anim_file)

Next steps

This tutorial has shown the complete code necessary to write and train a GAN. As a next step, you might like to experiment with a different dataset, for example the Large-scale Celeb Faces Attributes (CelebA) dataset available on Kaggle. To learn more about GANs see the NIPS 2016 Tutorial: Generative Adversarial Networks.