演算法原理

具體演算法原理，在這裡不再闡述，可以參考：

https://blog.csdn.net/stdcoutzyx/article/details/53872121
https://ask.julyedu.com/question/7681

基於keras的原始碼

from keras.models import Sequential
from keras.layers import Dense
from keras.layers import Reshape
from keras.layers.core import Activation
from keras.layers.normalization import BatchNormalization
from keras.layers.convolutional import UpSampling2D
from keras.layers.convolutional import Conv2D, MaxPooling2D
from keras.layers.core import Flatten
from keras.optimizers import SGD
from keras.datasets import mnist
import numpy as np
from PIL import Image
import argparse
import math


def generator_model():
    model = Sequential()
    model.add(Dense(input_dim=100, output_dim=1024))
    model.add(Activation('tanh'))
    model.add(Dense(128*7*7))
    model.add(BatchNormalization())
    model.add(Activation('tanh'))
    model.add(Reshape((7, 7, 128), input_shape=(128*7*7,)))
    model.add(UpSampling2D(size=(2, 2)))
    model.add(Conv2D(64, (5, 5), padding='same'))
    model.add(Activation('tanh'))
    model.add(UpSampling2D(size=(2, 2)))
    model.add(Conv2D(1, (5, 5), padding='same'))
    model.add(Activation('tanh'))
    return model


def discriminator_model():
    model = Sequential()
    model.add(
            Conv2D(64, (5, 5),
            padding='same',
            input_shape=(28, 28, 1))
            )
    model.add(Activation('tanh'))
    model.add(MaxPooling2D(pool_size=(2, 2)))
    model.add(Conv2D(128, (5, 5)))
    model.add(Activation('tanh'))
    model.add(MaxPooling2D(pool_size=(2, 2)))
    model.add(Flatten())
    model.add(Dense(1024))
    model.add(Activation('tanh'))
    model.add(Dense(1))
    model.add(Activation('sigmoid'))
    return model


def generator_containing_discriminator(g, d):
    model = Sequential()
    model.add(g)
    d.trainable = False
    model.add(d)
    return model


def combine_images(generated_images):
    num = generated_images.shape[0]
    width = int(math.sqrt(num))
    height = int(math.ceil(float(num)/width))
    shape = generated_images.shape[1:3]
    image = np.zeros((height*shape[0], width*shape[1]),
                     dtype=generated_images.dtype)
    for index, img in enumerate(generated_images):
        i = int(index/width)
        j = index % width
        image[i*shape[0]:(i+1)*shape[0], j*shape[1]:(j+1)*shape[1]] = \
            img[:, :, 0]
    return image


def train(BATCH_SIZE):
    (X_train, y_train), (X_test, y_test) = mnist.load_data()
    X_train = (X_train.astype(np.float32) - 127.5)/127.5
    X_train = X_train[:, :, :, None]
    X_test = X_test[:, :, :, None]
    # X_train = X_train.reshape((X_train.shape, 1) + X_train.shape[1:])
    d = discriminator_model()
    g = generator_model()
    d_on_g = generator_containing_discriminator(g, d)#使用判斷器來監督生成器的訓練
    d_optim = SGD(lr=0.0005, momentum=0.9, nesterov=True)
    g_optim = SGD(lr=0.0005, momentum=0.9, nesterov=True)
    g.compile(loss='binary_crossentropy', optimizer="SGD")#只有生成器
    d_on_g.compile(loss='binary_crossentropy', optimizer=g_optim)#編譯生成器
    d.trainable = True
    d.compile(loss='binary_crossentropy', optimizer=d_optim)#只有判斷器
    for epoch in range(100):
        print("Epoch is", epoch)
        print("Number of batches", int(X_train.shape[0]/BATCH_SIZE))
        for index in range(int(X_train.shape[0]/BATCH_SIZE)):#每輪有多少個step，資料/batch_size
            noise = np.random.uniform(-1, 1, size=(BATCH_SIZE, 100))#生成100維度的噪聲
            image_batch = X_train[index*BATCH_SIZE:(index+1)*BATCH_SIZE]
            generated_images = g.predict(noise, verbose=0)#生成器生成的影象
            if index % 20 == 0:
                image = combine_images(generated_images)#這個是把20張影象拼接起來，組成一個大影象
                image = image*127.5+127.5#從-1~1還原成0~255
                Image.fromarray(image.astype(np.uint8)).save(
                    str(epoch)+"_"+str(index)+".png")#儲存影象
            X = np.concatenate((image_batch, generated_images))
            y = [1] * BATCH_SIZE + [0] * BATCH_SIZE
            d_loss = d.train_on_batch(X, y)#訓練判斷器
            print("batch %d d_loss : %f" % (index, d_loss))
            noise = np.random.uniform(-1, 1, (BATCH_SIZE, 100))
            d.trainable = False#把判斷器凍結
            g_loss = d_on_g.train_on_batch(noise, [1] * BATCH_SIZE)#固定判斷器引數，訓練生成器
            d.trainable = True
            print("batch %d g_loss : %f" % (index, g_loss))
            if index % 10 == 9:
                #每更新十次，儲存模型
                g.save_weights('generator', True)
                d.save_weights('discriminator', True)

#載入訓練好的模型進行預測
def generate(BATCH_SIZE, nice=False):
    g = generator_model()
    g.compile(loss='binary_crossentropy', optimizer="SGD")
    g.load_weights('generator')
    #生成比較好的模型
    if nice:
        d = discriminator_model()
        d.compile(loss='binary_crossentropy', optimizer="SGD")
        d.load_weights('discriminator')
        noise = np.random.uniform(-1, 1, (BATCH_SIZE*20, 100))
        generated_images = g.predict(noise, verbose=1)
        d_pret = d.predict(generated_images, verbose=1)
        index = np.arange(0, BATCH_SIZE*20)
        index.resize((BATCH_SIZE*20, 1))
        pre_with_index = list(np.append(d_pret, index, axis=1))
        pre_with_index.sort(key=lambda x: x[0], reverse=True)
        nice_images = np.zeros((BATCH_SIZE,) + generated_images.shape[1:3], dtype=np.float32)
        nice_images = nice_images[:, :, :, None]
        for i in range(BATCH_SIZE):
            idx = int(pre_with_index[i][1])
            nice_images[i, :, :, 0] = generated_images[idx, :, :, 0]
        image = combine_images(nice_images)
    #生成一般的模型
    else:
        noise = np.random.uniform(-1, 1, (BATCH_SIZE, 100))
        generated_images = g.predict(noise, verbose=1)
        image = combine_images(generated_images)
    image = image*127.5+127.5
    Image.fromarray(image.astype(np.uint8)).save(
        "generated_image.png")


def get_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("--mode", type=str,default='train')
    parser.add_argument("--batch_size", type=int, default=128)
    parser.add_argument("--nice", dest="nice", action="store_true")
    parser.set_defaults(nice=False)
    args = parser.parse_args()
    return args

if __name__ == "__main__":
    args = get_args()
    if args.mode == "train":
        train(BATCH_SIZE=args.batch_size)
    elif args.mode == "generate":
        generate(BATCH_SIZE=args.batch_size, nice=args.nice)
 

實驗結果

迭代的次數還不夠，生成的效果不算太好，若有興趣，可以多增加迭代次數，會生成更好的影象。