python - 使用 Keras 随机增强图像

Question

我正在尝试使用 MNIST 数据集来学习 Keras 库。在 MNIST 中，有 60k 个训练图像和 10k 个验证图像。

在这两组中，我想对 30% 的图像进行增强。

datagen = ImageDataGenerator(horizontal_flip=True, vertical_flip=True)
datagen.fit(training_images)
datagen.fit(validation_images)

这不会增强图像，我不确定如何使用 model.fit_generator 方法。我当前的 model.fit 如下:

model.fit(training_images, training_labels, validation_data=(validation_images, validation_labels), epochs=10, batch_size=200, verbose=2)

如何对此数据集中的某些图像应用增强？

Answer 1

我尝试通过以下方式定义我自己的生成器:

from sklearn.model_selection import train_test_split
from six import next

def partial_flow(array, flags, generator, aug_percentage, batch_size):
    # Splitting data into arrays which will be augmented and which won't
    not_aug_array, not_aug_flags, aug_array, aug_flags = train_test_split(
        array,
        test_size=aug_percentage)
    # Preparation of generators which will be used for augmentation.
    aug_split_size = int(batch_size * split_size)
    # We will use generator without any augmentation to yield not augmented data
    not_augmented_gen = ImageDataGenerator()
    aug_gen = generator.flow(
        x=aug_array,
        y=aug_flags,
        batch_size=aug_split_size)
    not_aug_gen = not_augmented_gen.flow(
        x=not_aug_array,
        y=not_aug_flags,
        batch_size=batch_size - aug_split_size)
    # Yiedling data
    while True:
        # Getting augmented data
        aug_x, aug_y = next(aug_gen)
        # Getting not augmented data
        not_aug_x, not_aug_y = next(not_aug_gen)
        # Concatenation
        current_x = numpy.concatenate([aug_x, not_aug_x], axis=0)
        current_y = numpy.concatenate([aug_y, not_aug_y], axis=0)
        yield current_x, current_y

现在您可以通过以下方式进行训练:

 batch_size = 200
 model.fit_generator(partial_flow(training_images, training_labels, 0.7, batch_size),
                     steps_per_epoch=int(training_images.shape[0] / batch_size),
                     epochs=10,
                     validation_data=partial_flow(validation_images, validation_labels, 0.7, batch_size),
                     validation_steps=int(validation_images.shape[0] / batch_size))