NANOSCALE IMAGE PROCESSING - Bio-Inspired and Nanoscale Integrated Computing - page 519

3. Unfortunately, multiple unique figures may now have the same component
labels in terms of CL and CR. The labels are disambiguated by choosing the
row index of the topmost node with the column index CR to be the third
label component, T, of each figure. This label component is found on the last
column of the systolic reconfigurable mesh, as the image is piped out.
(a) All the boundary black nodes should now form a connected sub-bus.
For that, each node checks its neighbors and decide if it is a boundary
node (has at least a white neighbor). All the boundary nodes then
connect to their neighboring boundary nodes, forming a sub-bus.
(b) Next the local topmost nodes on the column CR are found by having
each node send a signal downwards in that column. This is done by
first turning off (disconnecting the channel) all the switches above each
node to force the signal downwards. Then all nodes simultaneously
send out a signal downwards and turn all switches on (reconnecting the
channel), thereby lettings all signals pass through the bus. Each node
that receives a signal will become disabled. As the result, the only active
nodes are the local topmost nodes that have not received a signal.
(c) If there is only one local topmost node in any figure, that will be the
topmost node chosen as the third label component. However, there
might be more than one local topmost node in a figure (in dented
figures). To solve this issue, each local bottommost node is used to
disable the local topmost node below it. The procedure of finding local
bottommost nodes is quite similar to the one finding the local topmost
nodes. Next, the switches at the topmost nodes are set so that they
won't let the signals go pass through them. To prevent the last
bottommost node to disable the first topmost node, the bottommost
nodes broadcast their row index. The immediate topmost node after
each bottommost node receives the row index and compares it to its
own.
If the signal is from a node with a row index higher than its own, that
topmost node gets disabled. At the end of this step only the ''top''
topmost node is not disabled, and the row index of that node is used to
label Figure 19.2, as explained in step (d). An example is shown in Figure
19.2 where first the local topmost and local bottommost nodes are
marked, and next the local topmost nodes are disabled by the bottom-
most nodes above them.
(d) The switches are set such that all the black nodes in each figure are
connected. The ''top'' topmost node broadcasts its row index to all the
nodes. Each black pixel which has not previously set its third label
component T saves the broadcasted value; otherwise, it won't over-
write the existing label.
4. In lockstep, shift the image to the right, so as to output the next column of
data (pixel and label information).