The polyline module interacts with the AVS5 image viewer,
to allow interactive line drawing on top of an image.
Points inside the image can be picked, and line segments
are drawn with "rubber banding" along the pick sequence.
"Undo" will back up the line segments, and clear will erase
all lines. If multiple image viewer "views" are open,
the rubber banding can be seen in each window at the same time.
The resulting picked polyline list is output on a
scatter field port, for external processing by other modules.