input_preprocess.py

"""Prepares the data used for DeepLab training/evaluation."""
import tensorflow as tf
from core import feature_extractor
from core import preprocess_utils


# The probability of flipping the images and labels
# left-right during training
_PROB_OF_FLIP = 0.5


def preprocess_image_and_label(image,
                               label,
                               crop_height,
                               crop_width,
                               min_resize_value=None,
                               max_resize_value=None,
                               resize_factor=None,
                               min_scale_factor=1.,
                               max_scale_factor=1.,
                               scale_factor_step_size=0,
                               ignore_label=255,
                               is_training=True,
                               model_variant=None):
    """Preprocesses the image and label.

    Args:
      image: Input image.
      label: Ground truth annotation label.
      crop_height: The height value used to crop the image and label.
      crop_width: The width value used to crop the image and label.
      min_resize_value: Desired size of the smaller image side.
      max_resize_value: Maximum allowed size of the larger image side.
      resize_factor: Resized dimensions are multiple of factor plus one.
      min_scale_factor: Minimum scale factor value.
      max_scale_factor: Maximum scale factor value.
      scale_factor_step_size: The step size from min scale factor to max scale
        factor. The input is randomly scaled based on the value of
        (min_scale_factor, max_scale_factor, scale_factor_step_size).
      ignore_label: The label value which will be ignored for training and
        evaluation.
      is_training: If the preprocessing is used for training or not.
      model_variant: Model variant (string) for choosing how to mean-subtract the
        images. See feature_extractor.network_map for supported model variants.

    Returns:
      original_image: Original image (could be resized).
      processed_image: Preprocessed image.
      label: Preprocessed ground truth segmentation label.

    Raises:
      ValueError: Ground truth label not provided during training.
    """
    if is_training and label is None:
        raise ValueError('During training, label must be provided.')
    if model_variant is None:
        tf.logging.warning('Default mean-subtraction is performed. Please specify '
                           'a model_variant. See feature_extractor.network_map for '
                           'supported model variants.')

    # Keep reference to original image.
    original_image = image

    processed_image = tf.cast(image, tf.float32)

    if label is not None:
        label = tf.cast(label, tf.int32)

    # Resize image and label to the desired range.
    if min_resize_value is not None or max_resize_value is not None:
        [processed_image, label] = (
            preprocess_utils.resize_to_range(
                image=processed_image,
                label=label,
                min_size=min_resize_value,
                max_size=max_resize_value,
                factor=resize_factor,
                align_corners=True))
        # The `original_image` becomes the resized image.
        original_image = tf.identity(processed_image)

    # Data augmentation by randomly scaling the inputs.
    if is_training:
        scale = preprocess_utils.get_random_scale(
            min_scale_factor, max_scale_factor, scale_factor_step_size)
        processed_image, label = preprocess_utils.randomly_scale_image_and_label(
            processed_image, label, scale)
        processed_image.set_shape([None, None, 3])

    # Pad image and label to have dimensions >= [crop_height, crop_width]
    image_shape = tf.shape(processed_image)
    image_height = image_shape[0]
    image_width = image_shape[1]

    target_height = image_height + tf.maximum(crop_height - image_height, 0)
    target_width = image_width + tf.maximum(crop_width - image_width, 0)

    # Pad image with mean pixel value.
    mean_pixel = tf.reshape(
        feature_extractor.mean_pixel(model_variant), [1, 1, 3])
    processed_image = preprocess_utils.pad_to_bounding_box(
        processed_image, 0, 0, target_height, target_width, mean_pixel)

    if label is not None:
        label = preprocess_utils.pad_to_bounding_box(
            label, 0, 0, target_height, target_width, ignore_label)

    # Randomly crop the image and label.
    if is_training and label is not None:
        processed_image, label = preprocess_utils.random_crop(
            [processed_image, label], crop_height, crop_width)

    processed_image.set_shape([crop_height, crop_width, 3])

    if label is not None:
        label.set_shape([crop_height, crop_width, 1])

    if is_training:
        # Randomly left-right flip the image and label.
        processed_image, label, _ = preprocess_utils.flip_dim(
            [processed_image, label], _PROB_OF_FLIP, dim=1)

    return original_image, processed_image, label