/// <summary>
/// Computes the signed area for a ring. The signed area is positive if the
/// <list type="Table">
/// <listheader>
/// <term>value</term>
/// <description>meaning</description>
/// </listheader>
/// <item><term>> 0</term>
/// <description>The ring is oriented clockwise (CW)</description></item>
/// <item><term>< 0</term>
/// <description>The ring is oriented counter clockwise (CCW)</description></item>
/// <item><term>== 0</term>
/// <description>The ring is degenerate or flat</description></item>
/// </list>
/// ring is oriented CW, negative if the ring is oriented CCW, and zero if the
/// ring is degenerate or flat.
/// </summary>
/// <param name="ring">The coordinates forming the ring</param>
/// <returns>The signed area of the ring</returns>
public static double OfRingSigned(CoordinateSequence ring)
{
int n = ring.Count;
if (n < 3)
{
return(0.0);
}
/**
* Based on the Shoelace formula.
* http://en.wikipedia.org/wiki/Shoelace_formula
*/
var p1 = ring.GetCoordinateCopy(0);
var p2 = ring.GetCoordinateCopy(1);
double x0 = p1.X;
p2.X -= x0;
double sum = 0.0;
for (int i = 1; i < n - 1; i++)
{
double p0Y = p1.Y;
p1.X = p2.X;
p1.Y = p2.Y;
ring.GetCoordinate(i + 1, p2);
p2.X -= x0;
sum += p1.X * (p0Y - p2.Y);
}
return(sum / 2.0);
}
/// <summary>
/// Computes the length of a <c>LineString</c> specified by a sequence of points.
/// </summary>
/// <param name="pts">The points specifying the <c>LineString</c></param>
/// <returns>The length of the <c>LineString</c></returns>
public static double OfLine(CoordinateSequence pts)
{
// optimized for processing CoordinateSequences
int n = pts.Count;
if (n <= 1)
{
return(0.0);
}
double len = 0.0;
var p = pts.GetCoordinateCopy(0);
double x0 = p.X;
double y0 = p.Y;
for (int i = 1; i < n; i++)
{
pts.GetCoordinate(i, p);
double x1 = p.X;
double y1 = p.Y;
double dx = x1 - x0;
double dy = y1 - y0;
len += Math.Sqrt(dx * dx + dy * dy);
x0 = x1;
y0 = y1;
}
return(len);
}
/// <summary>
/// Computes the locations of the nearest points between this sequence
/// and another sequence.
/// The locations are presented in the same order as the input sequences.
/// </summary>
/// <returns>A pair of <see cref="GeometryLocation"/>s for the nearest points.</returns>
public GeometryLocation[] NearestLocations(FacetSequence facetSeq)
{
bool isPoint = IsPoint;
bool isPointOther = facetSeq.IsPoint;
var locs = new GeometryLocation[2];
if (isPoint && isPointOther)
{
// DEVIATION (minor): JTS uses "new Coordinate(GetCoordinate(int))", which is worse
// than "GetCoordinateCopy(int)" for two reasons: 1) doesn't copy M (or, in NTS, Z),
// and 2) might allocate two Coordinate instances instead of one.
var pt = _pts.GetCoordinateCopy(_start);
var seqPt = facetSeq._pts.GetCoordinateCopy(facetSeq._start);
locs[0] = new GeometryLocation(_geom, _start, pt);
locs[1] = new GeometryLocation(facetSeq._geom, facetSeq._start, seqPt);
}
else if (isPoint)
{
var pt = _pts.GetCoordinateCopy(_start);
ComputeDistancePointLine(pt, facetSeq, locs);
}
else if (isPointOther)
{
var seqPt = facetSeq._pts.GetCoordinateCopy(facetSeq._start);
ComputeDistancePointLine(seqPt, this, locs);
// unflip the locations
(locs[0], locs[1]) = (locs[1], locs[0]);
}
else
{
ComputeDistanceLineLine(facetSeq, locs);
}
return(locs);
}
/// <summary>
/// Creates a new sequence based on a deep copy of the given <see cref="CoordinateSequence"/>.
/// </summary>
/// <param name="coordSeq">The coordinate sequence that will be copied</param>
public CoordinateArraySequence(CoordinateSequence coordSeq)
: base(coordSeq?.Count ?? 0, coordSeq?.Dimension ?? 2, coordSeq?.Measures ?? 0)
{
if (coordSeq == null)
{
Coordinates = new Coordinate[0];
return;
}
Coordinates = new Coordinate[coordSeq.Count];
for (int i = 0; i < Coordinates.Length; i++)
{
Coordinates[i] = coordSeq.GetCoordinateCopy(i);
}
}