Gets the length of the BinaryImage.


The length of the ChannelCollectionBase<(Of <(<'T>)>)> binary image is the combined length of all the items in the collection.
The default implementation assumes all IChannel items in the collection have the same length, hence the value returned is the BinaryLength()()()() of the first item in the collection times the Count.
The default implementation assumes all IChannel items in the collection have the same length, hence the value returned is the BinaryLength()()()() of the first item in the collection times the Count.