A string,
one of channels_last (default) or channels_first.
The ordering of the dimensions in the inputs.
channels_last corresponds to inputs with shape
(batch, height, width, channels) while channels_first
corresponds to inputs with shape
(batch, channels, height, width).
When unspecified, uses image_data_format value found
in your Keras config file at ~/.keras/keras.json
(if exists) else 'channels_last'. Defaults to 'channels_last'.
keepdims
A boolean, whether to keep the spatial dimensions or not.
If keepdims is False (default), the rank of the tensor is reduced
for spatial dimensions.
If keepdims is True, the spatial dimensions are retained with
length 1.
The behavior is the same as for tf.reduce_mean or np.mean.
Input shape
If data_format='channels_last':
4D tensor with shape (batch_size, rows, cols, channels).
If data_format='channels_first':
4D tensor with shape (batch_size, channels, rows, cols).
Output shape
If keepdims=False:
2D tensor with shape (batch_size, channels).
If keepdims=True:
If data_format='channels_last':
4D tensor with shape (batch_size, 1, 1, channels)
If data_format='channels_first':
4D tensor with shape (batch_size, channels, 1, 1)