[Pharo-project] ImageSegment vs SmartRefStream

Hi folks. I have been analyzing the code and trying to understand what ImageSegment does and how. After that, I came up to SmartRefStream and here is where I have some questions: 1) which is the difference between ImageSegment and SmartRefStream ? what does each of them do ? 2) Who uses who ? ImageSegment uses SmartRefStream or vice-versa? each one use the other? Thank you for any hints you can give me. Mariano