inputGeom property
Simplifies a geometry and ensures that the result is a valid geometry having the same dimension and number of components as the input, and with the components having the same topological relationship.
If the input is a polygonal geometry ( {@link Polygon} or {@link MultiPolygon} ):
- The result has the same number of shells and holes as the input, with the same topological structure
- The result rings touch at no more than the number of touching points in the input (although they may touch at fewer points). The key implication of this statement is that if the input is topologically valid, so is the simplified output.
For all geometry types, the result will contain enough vertices to ensure validity. For polygons and closed linear geometries, the result will have at least 4 vertices; for open linestrings the result will have at least 2 vertices.
All geometry types are handled. Empty and point geometries are returned unchanged. Empty geometry components are deleted.
The simplification uses a maximum-distance difference algorithm similar to the Douglas-Peucker algorithm.
KNOWN BUGS
- May create invalid topology if there are components which are small relative to the tolerance value. In particular, if a small hole is very near an edge, it is possible for the edge to be moved by a relatively large tolerance value and end up with the hole outside the result shell (or inside another hole). Similarly, it is possible for a small polygon component to end up inside a nearby larger polygon. A workaround is to test for this situation in post-processing and remove any invalid holes or polygons.
@author Martin Davis @see DouglasPeuckerSimplifier
Implementation
Geometry inputGeom;