Geotools JTS, find most distant points in polyline or polygon?

Question

is there any convenient API in JTS that would help to

• find two most distant points in line
• find two most distant points in polygon

Answer 1

I think all of the JTS methods relating to distance are looking for the nearest or shortest. But providing you don't have too many vertices then you could do a brute force O(N*N) search:

GeometryFactory gf = new GeometryFactory();
double maxDist = 0;
Point start = null, end = null;
for (Coordinate c : geom.getCoordinates()) {
  Point p = gf.createPoint(c);
  for (Coordinate c2 : geom.getCoordinates()) {
    Point p2 = gf.createPoint(c2);
    double d = DistanceOp.distance(p, p2);
    if (d > maxDist) {
      maxDist = d;
      start = p;
      end = p2;
    }
  }
} 

And if you need to consider points along the lines then add

geom = Densifier.densify(geom, .01);

before you start, though obviously this pushes N up.

Answer 2

You can use the MinimumBoundingCircle algorithm to do this.