tfds.features.Image

FeatureConnector for images.

Inherits From: FeatureConnector

During _generate_examples, the feature connector accept as input any of:

  • str: path to a {bmp,gif,jpeg,png} image (ex: /path/to/img.png).
  • np.array: 3d np.uint8 array representing an image.
  • A file object containing the png or jpeg encoded image string (ex: io.BytesIO(encoded_img_bytes))

tf.Tensor of type tf.uint8 and shape [height, width, num_channels] for BMP, JPEG, and PNG images and shape [num_frames, height, width, 3] for GIF images.

features=features.FeaturesDict({
    'input': features.Image(),
    'target': features.Image(shape=(None, None, 1), encoding_format='png'),
})
  • During generation:
yield {
    'input': 'path/to/img.jpg',
    'target': np.ones(shape=(64, 64, 1), dtype=np.uint8),
}

shape tuple of ints or None, the shape of decoded image. For GIF images: (num_frames, height, width, channels=3). num_frames, height and width can be None. For other images: (height, width, channels). height and width can be None. See tf.image.encode_* for doc on channels parameter. Defaults to (None, None, 3).
dtype tf.uint8 (default), tf.uint16 or tf.float32. * tf.uint16 requires png encoding_format. * tf.float32 only supports single-channel image. Internally float images are bitcasted to 4-channels tf.uint8 and saved as PNG.
encoding_format 'jpeg' or 'png'. Format to serialize np.ndarray images on disk. If None, encode images as PNG. If image is loaded from {bmg,gif,jpeg,png} file, this parameter is ignored, and file original encoding is used.
use_colormap Only used for gray-scale images. If True, tfds.as_dataframe will display each value in the image with a different color.
doc Documentation of this feature (e.g. description).

ValueError If the shape is invalid

doc

dtype Return the dtype (or dict of dtype) of this FeatureConnector.
encoding_format

numpy_dtype

shape Return the shape (or dict of shape) of this FeatureConnector.
use_colormap

Methods

catalog_documentation

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Returns the feature documentation to be shown in the catalog.

cls_from_name

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Returns the feature class for the given Python class.

decode_batch_example

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Decode multiple features batched in a single tf.Tensor.

This function is used to decode features wrapped in tfds.features.Sequence(). By default, this function apply decode_example on each individual elements using tf.map_fn. However, for optimization, features can overwrite this method to apply a custom batch decoding.

Args
tfexample_data Same tf.Tensor inputs as decode_example, but with and additional first dimension for the sequence length.

Returns
tensor_data Tensor or dictionary of tensor, output of the tf.data.Dataset object

decode_example

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Reconstruct the image from the tf example.

decode_ragged_example

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Decode nested features from a tf.RaggedTensor.

This function is used to decode features wrapped in nested tfds.features.Sequence(). By default, this function apply decode_batch_example on the flat values of the ragged tensor. For optimization, features can overwrite this method to apply a custom batch decoding.

Args
tfexample_data tf.RaggedTensor inputs containing the nested encoded examples.

Returns
tensor_data The decoded tf.RaggedTensor or dictionary of tensor, output of the tf.data.Dataset object

encode_example

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Convert the given image into a dict convertible to tf example.

from_config

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Reconstructs the FeatureConnector from the config file.

Usage:

features = FeatureConnector.from_config('path/to/dir')

Args
root_dir Directory containing the features.json file.

Returns
The reconstructed feature instance.

from_json

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FeatureConnector factory.

This function should be called from the tfds.features.FeatureConnector base class. Subclass should implement the from_json_content.

Example:

feature = tfds.features.FeatureConnector.from_json(
    {'type': 'Image', 'content': {'shape': [32, 32, 3], 'dtype': 'uint8'}}
)
assert isinstance(feature, tfds.features.Image)

Args
value dict(type=, content=) containing the feature to restore. Match dict returned by to_json.

Returns
The reconstructed FeatureConnector.

from_json_content

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FeatureConnector factory (to overwrite).

Subclasses should overwrite this method. This method is used when importing the feature connector from the config.

This function should not be called directly. FeatureConnector.from_json should be called instead.

See existing FeatureConnectors for implementation examples.

Args
value FeatureConnector information represented as either Json or a Feature proto. The content must match what is returned by to_json_content.
doc Documentation of this feature (e.g. description).

Returns
The reconstructed FeatureConnector.

from_proto

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Instantiates a feature from its proto representation.

get_serialized_info

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get_tensor_info

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get_tensor_spec

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Returns the tf.TensorSpec of this feature (not the element spec!).

Note that the output of this method may not correspond to the element spec of the dataset. For example, currently this method does not support RaggedTensorSpec.

load_metadata

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Restore the feature metadata from disk.

If a dataset is re-loaded and generated files exists on disk, this function will restore the feature metadata from the saved file.

Args
data_dir str, path to the dataset folder to which save the info (ex: ~/datasets/cifar10/1.2.0/)
feature_name str, the name of the feature (from the FeaturesDict key)

repr_html

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Images are displayed as thumbnail.

repr_html_batch

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Sequence(Image()) are displayed as <video>.

repr_html_ragged

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Returns the HTML str representation of the object (Nested sequence).

save_config

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Exports the FeatureConnector to a file.

Args
root_dir path/to/dir containing the features.json

save_metadata

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Save the feature metadata on disk.

This function is called after the data has been generated (by _download_and_prepare) to save the feature connector info with the generated dataset.

Some dataset/features dynamically compute info during _download_and_prepare. For instance:

  • Labels are loaded from the downloaded data
  • Vocabulary is created from the downloaded data
  • ImageLabelFolder compute the image dtypes/shape from the manual_dir

After the info have been added to the feature, this function allow to save those additional info to be restored the next time the data is loaded.

By default, this function do not save anything, but sub-classes can overwrite the function.

Args
data_dir str, path to the dataset folder to which save the info (ex: ~/datasets/cifar10/1.2.0/)
feature_name str, the name of the feature (from the FeaturesDict key)

to_json

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Exports the FeatureConnector to Json.

Each feature is serialized as a dict(type=..., content=...).

  • type: The cannonical name of the feature (module.FeatureName).
  • content: is specific to each feature connector and defined in to_json_content. Can contain nested sub-features (like for tfds.features.FeaturesDict and tfds.features.Sequence).

For example:

tfds.features.FeaturesDict({
    'input': tfds.features.Image(),
    'target': tfds.features.ClassLabel(num_classes=10),
})

Is serialized as:

{
    "type": "tensorflow_datasets.core.features.features_dict.FeaturesDict",
    "content": {
        "input": {
            "type": "tensorflow_datasets.core.features.image_feature.Image",
            "content": {
                "shape": [null, null, 3],
                "dtype": "uint8",
                "encoding_format": "png"
            }
        },
        "target": {
            "type":
            "tensorflow_datasets.core.features.class_label_feature.ClassLabel",
            "content": {
              "num_classes": 10
            }
        }
    }
}

Returns
A dict(type=, content=). Will be forwarded to from_json when reconstructing the feature.

to_json_content

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FeatureConnector factory (to overwrite).

This function should be overwritten by the subclass to allow re-importing the feature connector from the config. See existing FeatureConnector for example of implementation.

Returns
The FeatureConnector metadata in either a dict, or a Feature proto. This output is used in from_json_content when reconstructing the feature.

to_proto

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Exports the FeatureConnector to the Feature proto.

For features that have a specific schema defined in a proto, this function needs to be overriden. If there's no specific proto schema, then the feature will be represented using JSON.

Returns
The feature proto describing this feature.

ALIASES []