Image augmentation: cropping, flipping, and color transforms.

def image_augmentation(images, do_colors=False, crop_size=None):
  """Image augmentation: cropping, flipping, and color transforms."""
  if crop_size is None:
    crop_size = [299, 299]
  images = tf.random_crop(images, crop_size + [3])
  images = tf.image.random_flip_left_right(images)
  if do_colors:  # More augmentation, but might be slow.
    images = tf.image.random_brightness(images, max_delta=32. / 255.)
    images = tf.image.random_saturation(images, lower=0.5, upper=1.5)
    images = tf.image.random_hue(images, max_delta=0.2)
    images = tf.image.random_contrast(images, lower=0.5, upper=1.5)
  return images