public void TestProjectionFactor()
{
// zero-length line
var seg = new LineSegment(10, 0, 10, 0);
Assert.IsTrue(Double.IsNaN(seg.ProjectionFactor(new Coordinate(11, 0))));
var seg2 = new LineSegment(10, 0, 20, 0);
Assert.IsTrue(seg2.ProjectionFactor(new Coordinate(11, 0)) == 0.1);
}
/// <summary>
///
/// </summary>
/// <param name="seg"></param>
/// <param name="inputPt"></param>
/// <param name="segmentStartMeasure"></param>
/// <returns></returns>
private static double SegmentNearestMeasure(LineSegment seg, Coordinate inputPt, double segmentStartMeasure)
{
// found new minimum, so compute location distance of point
double projFactor = seg.ProjectionFactor(inputPt);
if (projFactor <= 0.0)
return segmentStartMeasure;
if (projFactor <= 1.0)
return segmentStartMeasure + projFactor * seg.Length;
// ASSERT: projFactor > 1.0
return segmentStartMeasure + seg.Length;
}
/**
* @param co
* input coordinate in the neighbourhood of the MLineString
* @param tolerance
* max. distance that co may be from this MLineString
* @return an MCoordinate on this MLineString with appropriate M-value
*/
public MCoordinate GetClosestPoint(ICoordinate co, double tolerance)
{
if (!this.IsMonotone(false))
{
throw new ApplicationException("MGeometryException.OPERATION_REQUIRES_MONOTONE");
}
if (!this.IsEmpty)
{
LineSegment seg = new LineSegment();
ICoordinate[] coAr = this.Coordinates;
seg.P0 = coAr[0];
double d = 0.0;
double projfact = 0.0;
double minDist = Double.PositiveInfinity;
MCoordinate mincp = null;
for (int i = 1; i < coAr.Length; i++)
{
seg.P1 = coAr[i];
ICoordinate cp = seg.ClosestPoint(co);
d = cp.Distance(co);
if (d <= tolerance && d <= minDist)
{
MCoordinate testcp = new MCoordinate(cp);
projfact = seg.ProjectionFactor(cp);
testcp.M = ((MCoordinate)coAr[i - 1]).M
+ projfact
* (((MCoordinate)coAr[i]).M - ((MCoordinate)coAr[i - 1]).M);
if (d < minDist || testcp.M < mincp.M)
{
mincp = testcp;
minDist = d;
}
}
seg.P0 = seg.P1;
}
if (minDist > tolerance)
{
return null;
}
else
{
return mincp;
}
}
else
{
return null;
}
}
