/// <summary>
/// The ringCoord is assumed to contain no repeated points.
/// It may be degenerate (i.e. contain only 1, 2, or 3 points).
/// In this case it has no area, and hence has a minimum diameter of 0.
/// </summary>
/// <param name="ringCoord"></param>
/// <param name="bufferDistance"></param>
/// <returns></returns>
private bool IsErodedCompletely(Coordinate[] ringCoord, double bufferDistance)
{
// degenerate ring has no area
if (ringCoord.Length < 4)
{
return(bufferDistance < 0);
}
// important test to eliminate inverted triangle bug
// also optimizes erosion test for triangles
if (ringCoord.Length == 4)
{
return(IsTriangleErodedCompletely(ringCoord, bufferDistance));
}
/*
* The following is a heuristic test to determine whether an
* inside buffer will be eroded completely.
* It is based on the fact that the minimum diameter of the ring pointset
* provides an upper bound on the buffer distance which would erode the
* ring.
* If the buffer distance is less than the minimum diameter, the ring
* may still be eroded, but this will be determined by
* a full topological computation.
*
*/
var ring = _inputGeom.Factory.CreateLinearRing(ringCoord);
var md = new MinimumDiameter(ring);
double minDiam = md.Length;
return(minDiam < 2 * Math.Abs(bufferDistance));
}
private void DoMinimumDiameterTest(bool convex, String wkt, Coordinate c0, Coordinate c1)
{
Coordinate[] minimumDiameter = new MinimumDiameter(new WKTReader().Read(wkt), convex).Diameter.Coordinates;
double tolerance = 1E-10;
Assert.AreEqual(c0.X, minimumDiameter[0].X, tolerance);
Assert.AreEqual(c0.Y, minimumDiameter[0].Y, tolerance);
Assert.AreEqual(c1.X, minimumDiameter[1].X, tolerance);
Assert.AreEqual(c1.Y, minimumDiameter[1].Y, tolerance);
}
