public Geobuf.Data.Geometry multiPolyToGeobuf(MultiPolygon poly) {
Geobuf.Data.Geometry.Builder builder =
Geobuf.Data.Geometry.newBuilder().setType(Geobuf.Data.Geometry.Type.MULTIPOLYGON);
// first we specify the number of polygons
builder.addLengths(poly.getNumGeometries());
for (int i = 0; i < poly.getNumGeometries(); i++) {
Polygon p = (Polygon) poly.getGeometryN(i);
// how many rings there are
builder.addLengths(p.getNumInteriorRing() + 1);
Stream<LineString> interiorRings =
IntStream.range(0, p.getNumInteriorRing()).<LineString>mapToObj(p::getInteriorRingN);
Stream.concat(Stream.of(p.getExteriorRing()), interiorRings)
.forEach(r -> addRing(r, builder));
}
return builder.build();
}
/** Add a ring to a builder */
private void addRing(LineString r, Geobuf.Data.Geometry.Builder builder) {
// skip last point, same as first
builder.addLengths(r.getNumPoints() - 1);
long x, y, prevX = 0, prevY = 0;
// last point is same as first, skip
for (int i = 0; i < r.getNumPoints() - 1; i++) {
// delta code
Coordinate coord = r.getCoordinateN(i);
// note that roundoff errors do not accumulate
x = (long) (coord.x * precisionMultiplier);
y = (long) (coord.y * precisionMultiplier);
builder.addCoords(x - prevX);
builder.addCoords(y - prevY);
prevX = x;
prevY = y;
}
}