access it via pointers (still to only 1 instance, now with a less
generic name).
Restructure the "and" and "or" masks as border and interior masks
(where the "and" mask was for the union of the border and the interior).
"and" and "or" were only a detail in a not very good implementation,
and after fixing that the union was only used to calculate the border
at runtime.
Use the metric data in more places to clip to active pixels earlier.
e560b71d3b