keras/keras_core/utils/image_dataset_utils.py

from keras_core.api_export import keras_core_export
from keras_core.utils.module_utils import tensorflow as tf


@keras_core_export(
    [
        "keras_core.utils.image_dataset_from_directory",
        "keras_core.preprocessing.image_dataset_from_directory",
    ]
)
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,
    crop_to_aspect_ratio=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`, `.jpg`, `.png`, `.bmp`, `.gif`.
    Animated gifs are truncated to the first frame.

    Args:
        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),
            `None` (no labels),
            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: String describing the encoding of `labels`. Options are:
            - `"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 explicit 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"`.
            Defaults to `"rgb"`. Whether the images will be converted to
            have 1, 3, or 4 channels.
        batch_size: Size of the batches of data. Defaults to 32.
            If `None`, the data will not be batched
            (the dataset will yield individual samples).
        image_size: Size to resize images to after they are read from disk,
            specified as `(height, width)`. 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. Defaults to `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: Subset of the data to return.
            One of `"training"`, `"validation"`, or `"both"`.
            Only used if `validation_split` is set.
            When `subset="both"`, the utility returns a tuple of two datasets
            (the training and validation datasets respectively).
        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 visit subdirectories pointed to by symlinks.
            Defaults to `False`.
        crop_to_aspect_ratio: If `True`, resize the images without aspect
            ratio distortion. When the original aspect ratio differs from the
            target aspect ratio, the output image will be cropped so as to
            return the largest possible window in the image
            (of size `image_size`) that matches the target aspect ratio. By
            default (`crop_to_aspect_ratio=False`), aspect ratio may not be
            preserved.

    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 `"categorical"`, 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 channels in the image tensors.
    - if `color_mode` is `"rgba"`,
        there are 4 channels in the image tensors.
    """
    # TODO: long-term, port implementation.
    return tf.keras.utils.image_dataset_from_directory(
        directory,
        labels=labels,
        label_mode=label_mode,
        class_names=class_names,
        color_mode=color_mode,
        batch_size=batch_size,
        image_size=image_size,
        shuffle=shuffle,
        seed=seed,
        validation_split=validation_split,
        subset=subset,
        interpolation=interpolation,
        follow_links=follow_links,
        crop_to_aspect_ratio=crop_to_aspect_ratio,
    )