Dissolve can locate and enclose a connected polygonal
region (in box coordinates) containing equi-valued pixels.
The traversal needs to be written to create the polygon in
coordinate space and zero edges in box coordinates, leaving
the pixel marks (in box coordinates) in place.  README.md
modified to include new help. Possible modifications:
nodata could be flagged as "visited." (even,even) coordinates
in box space could be marked to guide the traversal (maybe).