keras-team/keras · error · ValueError

{self._VALUE_RANGE_VALIDATION_ERROR}Received: value_range={v

Error message

{self._VALUE_RANGE_VALIDATION_ERROR}Received: value_range={value_range}

What it means

AutoContrast and other image preprocessing layers sharing this helper require value_range to be a tuple or list describing the valid pixel range of the input images, e.g. (0, 255) or (0.0, 1.0). The constructor raises this ValueError when value_range is not a tuple/list at all - for example a bare int, a string, or None.

Source

Thrown at keras/src/layers/preprocessing/image_preprocessing/auto_contrast.py:46

            Defaults to `(0, 255)`.
    """

    _USE_BASE_FACTOR = False
    _VALUE_RANGE_VALIDATION_ERROR = (
        "The `value_range` argument should be a list of two numbers. "
    )

    def __init__(
        self,
        value_range=(0, 255),
        **kwargs,
    ):
        super().__init__(**kwargs)
        self._set_value_range(value_range)

    def _set_value_range(self, value_range):
        if not isinstance(value_range, (tuple, list)):
            raise ValueError(
                self._VALUE_RANGE_VALIDATION_ERROR
                + f"Received: value_range={value_range}"
            )
        if len(value_range) != 2:
            raise ValueError(
                self._VALUE_RANGE_VALIDATION_ERROR
                + f"Received: value_range={value_range}"
            )
        self.value_range = sorted(value_range)

    def transform_images(self, images, transformation=None, training=True):
        original_images = images
        images = self._transform_value_range(
            images,
            original_range=self.value_range,
            target_range=(0, 255),
            dtype=self.compute_dtype,
        )

View on GitHub (pinned to 7a34a03db6)

Solutions

1. Pass a two-element tuple/list matching your data, e.g. value_range=(0, 255) for uint8 images or (0.0, 1.0) for normalized floats.
2. Ensure the value is a literal tuple/list, not a scalar or string.

Example fix

# before
layer = keras.layers.AutoContrast(value_range=255)
# after
layer = keras.layers.AutoContrast(value_range=(0, 255))

assert isinstance(value_range, (tuple, list)), f"value_range must be tuple/list, got {type(value_range)}"

def is_valid_value_range(v):
    return isinstance(v, (tuple, list)) and len(v) == 2

When it happens

Trigger: keras.layers.AutoContrast(value_range=255), value_range=None, or value_range="0-255".

Common situations: Assuming value_range is a single max value; forgetting the argument in code that builds layers from a config dict where the key may be absent or set to a scalar.

Understand the failure class

Background: Invalid argument type errors: "must be of type string", "expected X, got Y", and ERR_INVALID_ARG_TYPE explained — this error's family across 15 libraries.

Related errors

• The `value_range` argument should be a list of two numbers.
• Layer {self.__class__.__name__} does not take a `factor` arg
• The `factor` argument should be a number (or a list of two n
• Invalid quantization mode. Expected one of {dtype_policies.Q
• Invalid value for argument `output_mode`. Expected one of {a

AI-assisted analysis of keras-team/keras@7a34a03db6 (2026-08-25). Data as JSON: /api/errors/2fe56f05c7d59441. Report an issue: GitHub.