One hot encoding of label map

Let’s say I have a label map with 0: background and 1: label

I am implementing an autoencoder that takes the input label and extends it to be a multi-label where each label is converted into a separate channel.

Now my question: When using the one hot encoder with a label map that has only one label (1), would the number of classes that I put into the on hot encoder be C=1 or C=2?

I am not sure if the one hot encoder converts the 0 values in its own channel. Would it?

Thanks a lot for your response.

@ptrblck Maybe you have an answer for this? I hope my question is clear enough.