text: # Copyright 2020 The TensorFlow Authors. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
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  # ==============================================================================
  """Keras image dataset loading utilities."""
  # pylint: disable=g-classes-have-attributes
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import numpy as np
  
  from tensorflow.python.data.ops import dataset_ops
  from tensorflow.python.keras.layers.preprocessing import image_preprocessing
  from tensorflow.python.keras.preprocessing import dataset_utils
  from tensorflow.python.ops import image_ops
  from tensorflow.python.ops import io_ops
  from tensorflow.python.util.tf_export import keras_export
  
  
  WHITELIST_FORMATS = ('.bmp', '.gif', '.jpeg', '.jpg', '.png')
  
  
  @keras_export('keras.preprocessing.image_dataset_from_directory', v1=[])
  def image_dataset_from_directory(directory,
                                   labels='inferred',
                                   label_mode='int',
                                   class_names=None,
                                   color_mode='rgb',
                                   batch_size=32,
                                   image_size=(256, 256),
                                   shuffle=True,
                                   seed=None,
                                   validation_split=None,
                                   subset=None,
                                   interpolation='bilinear',
                                   follow_links=False):
    """Generates a `tf.data.Dataset` from image files in a directory.
  
    If your directory structure is:
  
    ```
    main_directory/
    ...class_a/
    ......a_image_1.jpg
    ......a_image_2.jpg
    ...class_b/
    ......b_image_1.jpg
    ......b_image_2.jpg
    ```
  
    Then calling `image_dataset_from_directory(main_directory, labels='inferred')`
    will return a `tf.data.Dataset` that yields batches of images from
    the subdirectories `class_a` and `class_b`, together with labels
    0 and 1 (0 corresponding to `class_a` and 1 corresponding to `class_b`).
  
    Supported image formats: jpeg, png, bmp, gif.
    Animated gifs are truncated to the first frame.
  
    Arguments:
      directory: Directory where the data is located.
          If `labels` is "inferred", it should contain
          subdirectories, each containing images for a class.
          Otherwise, the directory structure is ignored.
      labels: Either "inferred"
          (labels are generated from the directory structure),
          or a list/tuple of integer labels of the same size as the number of
          image files found in the directory. Labels should be sorted according
          to the alphanumeric order of the image file paths
          (obtained via `os.walk(directory)` in Python).
      label_mode:
          - 'int': means that the labels are encoded as integers
              (e.g. for `sparse_categorical_crossentropy` loss).
          - 'categorical' means that the labels are
              encoded as a categorical vector
              (e.g. for `categorical_crossentropy` loss).
          - 'binary' means that the labels (there can be only 2)
              are encoded as `float32` scalars with values 0 or 1
              (e.g. for `binary_crossentropy`).
          - None (no labels).
      class_names: Only valid if "labels" is "inferred". This is the explict
          list of class names (must match names of subdirectories). Used
          to control the order of the classes
          (otherwise alphanumerical order is used).
      color_mode: One of "grayscale", "rgb", "rgba". Default: "rgb".
          Whether the images will be converted to
          have 1, 3, or 4 channels.
      batch_size: Size of the batches of data. Default: 32.
      image_size: Size to resize images to after they are read from disk.
          Defaults to `(256, 256)`.
          Since the pipeline processes batches of images that must all have
          the same size, this must be provided.
      shuffle: Whether to shuffle the data. Default: True.
          If set to False, sorts the data in alphanumeric order.
      seed: Optional random seed for shuffling and transformations.
      validation_split: Optional float between 0 and 1,
          fraction of data to reserve for validation.
      subset: One of "training" or "validation".
          Only used if `validation_split` is set.
      interpolation: String, the interpolation method used when resizing images.
        Defaults to `bilinear`. Supports `bilinear`, `nearest`, `bicubic`,
        `area`, `lanczos3`, `lanczos5`, `gaussian`, `mitchellcubic`.
      follow_links: Whether to visits subdirectories pointed to by symlinks.
          Defaults to False.
  
    Returns:
      A `tf.data.Dataset` object.
        - If `label_mode` is None, it yields `float32` tensors of shape
          `(batch_size, image_size[0], image_size[1], num_channels)`,
          encoding images (see below for rules regarding `num_channels`).
        - Otherwise, it yields a tuple `(images, labels)`, where `images`
          has shape `(batch_size, image_size[0], image_size[1], num_channels)`,
          and `labels` follows the format described below.
  
    Rules regarding labels format:
      - if `label_mode` is `int`, the labels are an `int32` tensor of shape
        `(batch_size,)`.
      - if `label_mode` is `binary`, the labels are a `float32` tensor of
        1s and 0s of shape `(batch_size, 1)`.
      - if `label_mode` is `categorial`, the labels are a `float32` tensor
        of shape `(batch_size, num_classes)`, representing a one-hot
        encoding of the class index.
  
    Rules regarding number of channels in the yielded images:
      - if `color_mode` is `grayscale`,
        there's 1 channel in the image tensors.
      - if `color_mode` is `rgb`,
        there are 3 channel in the image tensors.
      - if `color_mode` is `rgba`,
        there are 4 channel in the image tensors.
    """
    if labels != 'inferred':
      if not isinstance(labels, (list, tuple)):
        raise ValueError(
            '`labels` argument should be a list/tuple of integer labels, of '
            'the same size as the number of image files in the target '
            'directory. If you wish to infer the labels from the subdirectory '
            'names in the target directory, pass `labels="inferred"`. '
            'If you wish to get a dataset that only contains images '
            '(no labels), pass `labels=None`.')
      if class_names:
        raise ValueError('You can only pass `class_names` if the labels are '
                         'inferred from the subdirectory names in the target '
                         'directory (`labels="inferred"`).')
    if label_mode not in {'int', 'categorical', 'binary', None}:
      raise ValueError(
          '`label_mode` argument must be one of "int", "categorical", "binary", '
          'or None. Received: %s' % (label_mode,))
    if color_mode == 'rgb':
      num_channels = 3
    elif color_mode == 'rgba':
      num_channels = 4
    elif color_mode == 'grayscale':
      num_channels = 1
    else:
      raise ValueError(
          '`color_mode` must be one of {"rbg", "rgba", "grayscale"}. '
          'Received: %s' % (color_mode,))
    interpolation = image_preprocessing.get_interpolation(interpolation)
    dataset_utils.check_validation_split_arg(
        validation_split, subset, shuffle, seed)
  
    if seed is None:
      seed = np.random.randint(1e6)
    image_paths, labels, class_names = dataset_utils.index_directory(
        directory,
        labels,
        formats=WHITELIST_FORMATS,
        class_names=class_names,
        shuffle=shuffle,
        seed=seed,
        follow_links=follow_links)
  
    if label_mode == 'binary' and len(class_names) != 2:
      raise ValueError(
          'When passing `label_mode="binary", there must exactly 2 classes. '
          'Found the following classes: %s' % (class_names,))
  
    image_paths, labels = dataset_utils.get_training_or_validation_split(
        image_paths, labels, validation_split, subset)
  
    dataset = paths_and_labels_to_dataset(
        image_paths=image_paths,
        image_size=image_size,
        num_channels=num_channels,
        labels=labels,
        label_mode=label_mode,
        num_classes=len(class_names),
        interpolation=interpolation)
    if shuffle:
      # Shuffle locally at each iteration
      dataset = dataset.shuffle(buffer_size=batch_size * 8, seed=seed)
    dataset = dataset.batch(batch_size)
    # Users may need to reference `class_names`.
    dataset.class_names = class_names
    return dataset
  
  
  def paths_and_labels_to_dataset(image_paths,
                                  image_size,
                                  num_channels,
                                  labels,
                                  label_mode,
                                  num_classes,
                                  interpolation):
    """Constructs a dataset of images and labels."""
    # TODO(fchollet): consider making num_parallel_calls settable
    path_ds = dataset_ops.Dataset.from_tensor_slices(image_paths)
    img_ds = path_ds.map(
        lambda x: path_to_image(x, image_size, num_channels, interpolation))
    if label_mode:
      label_ds = dataset_utils.labels_to_dataset(labels, label_mode, num_classes)
      img_ds = dataset_ops.Dataset.zip((img_ds, label_ds))
    return img_ds
  
  
  def path_to_image(path, image_size, num_channels, interpolation):
    img = io_ops.read_file(path)
    img = image_ops.decode_image(
        img, channels=num_channels, expand_animations=False)
    img = image_ops.resize_images_v2(img, image_size, method=interpolation)
    img.set_shape((image_size[0], image_size[1], num_channels))
    return img
  