code: public RegionMap regionMap( GridCoverage2D grid ) {
          return regionMaps.computeIfAbsent(grid.hashCode(), key -> {
              return CoverageUtilities.getRegionParamsFromGridCoverage(grid);
          });
      }
docs: Calculates the {@link RegionMap} for the given grid by calling
  {@link CoverageUtilities#getRegionParamsFromGridCoverage(GridCoverage2D)}. The
  result is cached and re-used.