tensorflow/models · error · ValueError

len(stddev) must match the number of channels

Error message

len(stddev) must match the number of channels

What it means

Error "len(stddev) must match the number of channels" thrown in tensorflow/models.

Source

Thrown at official/legacy/image_classification/preprocessing.py:109

  Args:
    image_bytes: a tensor of size [height, width, C].
    stddev: a C-vector of values to divide from each channel.
    num_channels: number of color channels in the image that will be distorted.
    dtype: the dtype to convert the images to. Set to `None` to skip conversion.

  Returns:
    the centered image.

  Raises:
    ValueError: If the rank of `image` is unknown, if `image` has a rank other
      than three or if the number of channels in `image` doesn't match the
      number of values in `stddev`.
  """
  if image_bytes.get_shape().ndims != 3:
    raise ValueError('Input must be of size [height, width, C>0]')

  if len(stddev) != num_channels:
    raise ValueError('len(stddev) must match the number of channels')

  # We have a 1-D tensor of stddev; convert to 3-D.
  # Note(b/130245863): we explicitly call `broadcast` instead of simply
  # expanding dimensions for better performance.
  stddev = tf.broadcast_to(stddev, tf.shape(image_bytes))
  if dtype is not None:
    stddev = tf.cast(stddev, dtype=dtype)

  return image_bytes / stddev


def normalize_images(features: tf.Tensor,
                     mean_rgb: Tuple[float, ...] = MEAN_RGB,
                     stddev_rgb: Tuple[float, ...] = STDDEV_RGB,
                     num_channels: int = 3,
                     dtype: tf.dtypes.DType = tf.float32,
                     data_format: Text = 'channels_last') -> tf.Tensor:
  """Normalizes the input image channels with the given mean and stddev.

View on GitHub (pinned to e006f5f0d5)

When it happens

Trigger: Thrown at official/legacy/image_classification/preprocessing.py:109 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of tensorflow/models@e006f5f0d5 (2026-08-24). Data as JSON: /api/errors/13a6bb57bf29e6fe. Report an issue: GitHub.