image_dataset_from_directory: Create a dataset from a directory

In keras: R Interface to 'Keras'

Create a dataset from a directory

Description

Generates a tf.data.Dataset from image files in a directory.

Usage

image_dataset_from_directory(
  directory,
  labels = "inferred",
  label_mode = "int",
  class_names = NULL,
  color_mode = "rgb",
  batch_size = 32,
  image_size = c(256, 256),
  shuffle = TRUE,
  seed = NULL,
  validation_split = NULL,
  subset = NULL,
  interpolation = "bilinear",
  follow_links = FALSE,
  crop_to_aspect_ratio = FALSE,
  ...
)

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	Valid values: 'int': labels are encoded as integers (e.g. for sparse_categorical_crossentropy loss). 'categorical': labels are encoded as a categorical vector (e.g. for categorical_crossentropy loss). 'binary': labels (there can be only 2) are encoded as float32 scalars with values 0 or 1 (e.g. for binary_crossentropy). NULL: (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", "validation", or "both" (available for TF>=2.10). 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 visits 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.
...	Legacy arguments

Details

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.

Value

A tf.data.Dataset object. If label_mode is NULL, it yields float32 tensors of shape ⁠(batch_size, image_size[1], image_size[2], num_channels)⁠, encoding images (see below for rules regarding num_channels).

Otherwise, it yields pairs of ⁠(images, labels)⁠, where images has shape ⁠(batch_size, image_size[1], image_size[2], 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.

See Also

https://www.tensorflow.org/api_docs/python/tf/keras/utils/image_dataset_from_directory

keras documentation built on May 29, 2024, 3:20 a.m.