Hi

I have a few of questions about the description of the LBP for image completion algorithm

1. What do you mean by fixing the values of the pixels that are observed?

I don't see where that could affect the propagated messages, since for every edge we are basically going over all possible assignment (0-255)

We thought about fixing the incoming message of observed pixels to 1 if the value is the actual value and 0 otherwise but that doesn't make sense since in that way only the nodes surrounding the unobserved nodes will have an effect on them.

My question is where can we use the fact that a node is an observed pixel when iterating and updating the messages? since the equations use only phi(xi,xj) which is not affected by the actual value of the pixel (it is just a distribution over all possible values).

2. Why is it suggested to go only over the unobserved nodes and update the messages that leave from them? their MAP value depends on their incoming messages and if we don't update the messages leaving the observed nodes, how will they affect the unobserved ones?

3. Since this is a loopy BP should we initialize all the messages with a certain value (like 0)? since every node depends on another one and in order to update a message between node i to node j we need the values of the incoming messages of node i. Should we assume at first that node j has no incoming messages if our first update is from node i to node j?

thanks in advance!