/// <summary>
///
/// </summary>
/// <param name="p"></param>
/// <param name="seg"></param>
private void TestLineSegment(ICoordinate p, LineSegment seg)
{
double xInt; // x intersection of segment with ray
double x1; // translated coordinates
double y1;
double x2;
double y2;
/*
* Test if segment crosses ray from test point in positive x direction.
*/
ICoordinate p1 = seg.P0;
ICoordinate p2 = seg.P1;
x1 = p1.X - p.X;
y1 = p1.Y - p.Y;
x2 = p2.X - p.X;
y2 = p2.Y - p.Y;
if (((y1 > 0) && (y2 <= 0)) || ((y2 > 0) && (y1 <= 0)))
{
/*
* segment straddles x axis, so compute intersection.
*/
xInt = RobustDeterminant.SignOfDet2x2(x1, y1, x2, y2) / (y2 - y1);
/*
* crosses ray if strictly positive intersection.
*/
if (0.0 < xInt)
crossings++;
}
}
/// <summary>
///
/// </summary>
/// <param name="seg"></param>
/// <param name="inputPt"></param>
/// <returns></returns>
public static double SegmentFraction(LineSegment seg, ICoordinate inputPt)
{
double segFrac = seg.ProjectionFactor(inputPt);
if (segFrac < 0.0)
segFrac = 0.0;
else if (segFrac > 1.0)
segFrac = 1.0;
return segFrac;
}
/// <summary>
///
/// </summary>
/// <param name="querySeg"></param>
/// <returns></returns>
public IList Query(LineSegment querySeg)
{
Envelope env = new Envelope(querySeg.P0, querySeg.P1);
LineSegmentVisitor visitor = new LineSegmentVisitor(querySeg);
index.Query(env, visitor);
IList itemsFound = visitor.Items;
return itemsFound;
}
/// <summary>
///
/// </summary>
private void BuildIndex()
{
sirTree = new SIRtree();
ICoordinate[] pts = ring.Coordinates;
for (int i = 1; i < pts.Length; i++)
{
if (pts[i - 1].Equals(pts[i]))
continue;
LineSegment seg = new LineSegment(pts[i - 1], pts[i]);
sirTree.Insert(seg.P0.Y, seg.P1.Y, seg);
}
}
/// <summary>
/// Compare two collinear segments for left-most ordering.
/// If segs are vertical, use vertical ordering for comparison.
/// If segs are equal, return 0.
/// Segments are assumed to be directed so that the second coordinate is >= to the first
/// (e.g. up and to the right).
/// </summary>
/// <param name="seg0">A segment to compare.</param>
/// <param name="seg1">A segment to compare.</param>
/// <returns></returns>
private int CompareX(LineSegment seg0, LineSegment seg1)
{
int compare0 = seg0.P0.CompareTo(seg1.P0);
if (compare0 != 0) return compare0;
return seg0.P1.CompareTo(seg1.P1);
}
/// <summary>
///
/// </summary>
/// <param name="seg"></param>
/// <param name="depth"></param>
public DepthSegment(LineSegment seg, int depth)
{
// input seg is assumed to be normalized
upwardSeg = new LineSegment(seg);
this.leftDepth = depth;
}
/// <summary>
/// Computes the distance between this line segment and another one.
/// </summary>
/// <param name="ls"></param>
/// <returns></returns>
public double Distance(LineSegment ls)
{
return CGAlgorithms.DistanceLineLine(P0, P1, ls.P0, ls.P1);
}
/// <summary>
/// Returns <c>true</c> if <c>other</c> is
/// topologically equal to this LineSegment (e.g. irrespective
/// of orientation).
/// </summary>
/// <param name="other">
/// A <c>LineSegment</c> with which to do the comparison.
/// </param>
/// <returns>
/// <c>true</c> if <c>other</c> is a <c>LineSegment</c>
/// with the same values for the x and y ordinates.
/// </returns>
public bool EqualsTopologically(LineSegment other)
{
return
P0.Equals(other.P0) && P1.Equals(other.P1) ||
P0.Equals(other.P1) && P1.Equals(other.P0);
}
/// <summary>
///
/// </summary>
/// <param name="line"></param>
/// <param name="pt"></param>
/// <param name="locGeom"></param>
private void ComputeMinDistance(ILineString line, IPoint pt, GeometryLocation[] locGeom)
{
if (line.EnvelopeInternal.Distance(pt.EnvelopeInternal) > minDistance) return;
ICoordinate[] coord0 = line.Coordinates;
ICoordinate coord = pt.Coordinate;
// brute force approach!
for (int i = 0; i < coord0.Length - 1; i++)
{
double dist = CGAlgorithms.DistancePointLine(coord, coord0[i], coord0[i + 1]);
if (dist < minDistance)
{
minDistance = dist;
LineSegment seg = new LineSegment(coord0[i], coord0[i + 1]);
ICoordinate segClosestPoint = seg.ClosestPoint(coord);
locGeom[0] = new GeometryLocation(line, i, segClosestPoint);
locGeom[1] = new GeometryLocation(pt, 0, coord);
}
if (minDistance <= terminateDistance)
return;
}
}
/// <summary>
/// This is a convenience function which can be overridden to obtain the actual
/// line segments which overlap.
/// </summary>
/// <param name="seg1"></param>
/// <param name="seg2"></param>
public virtual void Overlap(LineSegment seg1, LineSegment seg2)
{
}
/// <summary>
/// Determines the orientation of a LineSegment relative to this segment.
/// The concept of orientation is specified as follows:
/// Given two line segments A and L,
/// A is to the left of a segment L if A lies wholly in the
/// closed half-plane lying to the left of L
/// A is to the right of a segment L if A lies wholly in the
/// closed half-plane lying to the right of L
/// otherwise, A has indeterminate orientation relative to L. This
/// happens if A is collinear with L or if A crosses the line determined by L.
/// </summary>
/// <param name="seg">The <c>LineSegment</c> to compare.</param>
/// <returns>
/// 1 if <c>seg</c> is to the left of this segment,
/// -1 if <c>seg</c> is to the right of this segment,
/// 0 if <c>seg</c> has indeterminate orientation relative to this segment.
/// </returns>
public int OrientationIndex(LineSegment seg)
{
int orient0 = CGAlgorithms.OrientationIndex(P0, P1, seg.P0);
int orient1 = CGAlgorithms.OrientationIndex(P0, P1, seg.P1);
// this handles the case where the points are Curve or collinear
if (orient0 >= 0 && orient1 >= 0)
return Math.Max(orient0, orient1);
// this handles the case where the points are R or collinear
if (orient0 <= 0 && orient1 <= 0)
return Math.Max(orient0, orient1);
// points lie on opposite sides ==> indeterminate orientation
return 0;
}
/// <summary>
///
/// </summary>
/// <param name="ls"></param>
public override void Select(LineSegment ls)
{
container.TestLineSegment(p, ls);
}
/// <summary>
///
/// </summary>
/// <param name="inputPt"></param>
/// <param name="minIndex"></param>
/// <returns></returns>
private double IndexOfFromStart(ICoordinate inputPt, double minIndex)
{
double minDistance = Double.MaxValue;
double ptMeasure = minIndex;
double segmentStartMeasure = 0.0;
LineSegment seg = new LineSegment();
foreach(LinearIterator.LinearElement element in new LinearIterator(linearGeom))
{
if (!element.IsEndOfLine)
{
seg.P0 = element.SegmentStart;
seg.P1 = element.SegmentEnd;
double segDistance = seg.Distance(inputPt);
double segMeasureToPt = SegmentNearestMeasure(seg, inputPt, segmentStartMeasure);
if (segDistance < minDistance && segMeasureToPt > minIndex)
{
ptMeasure = segMeasureToPt;
minDistance = segDistance;
}
segmentStartMeasure += seg.Length;
}
}
return ptMeasure;
}
/// <summary>
/// This is a convenience function which can be overridden to obtain the actual
/// line segment which is selected.
/// </summary>
/// <param name="seg"></param>
public virtual void Select(LineSegment seg)
{
}
/// <summary>
///
/// </summary>
/// <param name="ls"></param>
public void SetCoordinates(LineSegment ls)
{
SetCoordinates(ls.P0, ls.P1);
}
/// <summary>
///
/// </summary>
/// <param name="ls"></param>
public LineSegment(LineSegment ls)
: this(ls.p0, ls.p1)
{
}
/// <summary>
/// Project a line segment onto this line segment and return the resulting
/// line segment. The returned line segment will be a subset of
/// the target line line segment. This subset may be null, if
/// the segments are oriented in such a way that there is no projection.
/// Note that the returned line may have zero length (i.e. the same endpoints).
/// This can happen for instance if the lines are perpendicular to one another.
/// </summary>
/// <param name="seg">The line segment to project.</param>
/// <returns>The projected line segment, or <c>null</c> if there is no overlap.</returns>
public LineSegment Project(LineSegment seg)
{
double pf0 = ProjectionFactor(seg.P0);
double pf1 = ProjectionFactor(seg.P1);
// check if segment projects at all
if (pf0 >= 1.0 && pf1 >= 1.0) return null;
if (pf0 <= 0.0 && pf1 <= 0.0) return null;
ICoordinate newp0 = Project(seg.P0);
if (pf0 < 0.0) newp0 = P0;
if (pf0 > 1.0) newp0 = P1;
ICoordinate newp1 = Project(seg.P1);
if (pf1 < 0.0) newp1 = P0;
if (pf1 > 1.0) newp1 = P1;
return new LineSegment(newp0, newp1);
}
/// <summary>
///
/// </summary>
/// <param name="geom"></param>
private void ComputeWidthConvex(IGeometry geom)
{
ICoordinate[] pts = null;
if (geom is IPolygon)
pts = ((IPolygon) geom).ExteriorRing.Coordinates;
else pts = geom.Coordinates;
// special cases for lines or points or degenerate rings
if (pts.Length == 0)
{
minWidth = 0.0;
minWidthPt = null;
minBaseSeg = null;
}
else if (pts.Length == 1)
{
minWidth = 0.0;
minWidthPt = pts[0];
minBaseSeg.P0 = pts[0];
minBaseSeg.P1 = pts[0];
}
else if (pts.Length == 2 || pts.Length == 3)
{
minWidth = 0.0;
minWidthPt = pts[0];
minBaseSeg.P0 = pts[0];
minBaseSeg.P1 = pts[1];
}
else ComputeConvexRingMinDiameter(pts);
}
/// <summary>
///
/// </summary>
/// <param name="seg"></param>
/// <param name="inputPt"></param>
/// <param name="segmentStartMeasure"></param>
/// <returns></returns>
private double SegmentNearestMeasure(LineSegment seg, ICoordinate 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;
}
/// <summary>
/// Computes an intersection point between two segments, if there is one.
/// There may be 0, 1 or many intersection points between two segments.
/// If there are 0, null is returned. If there is 1 or more, a single one
/// is returned (chosen at the discretion of the algorithm). If
/// more information is required about the details of the intersection,
/// the {RobustLineIntersector} class should be used.
/// </summary>
/// <param name="line"></param>
/// <returns> An intersection point, or <c>null</c> if there is none.</returns>
public ICoordinate Intersection(LineSegment line)
{
LineIntersector li = new RobustLineIntersector();
li.ComputeIntersection(P0, P1, line.P0, line.P1);
if (li.HasIntersection)
return li.GetIntersection(0);
return null;
}
/// <summary>
/// Compute the width information for a ring of <c>Coordinate</c>s.
/// Leaves the width information in the instance variables.
/// </summary>
/// <param name="pts"></param>
private void ComputeConvexRingMinDiameter(ICoordinate[] pts)
{
// for each segment in the ring
minWidth = Double.MaxValue;
int currMaxIndex = 1;
LineSegment seg = new LineSegment();
// compute the max distance for all segments in the ring, and pick the minimum
for (int i = 0; i < pts.Length - 1; i++)
{
seg.P0 = pts[i];
seg.P1 = pts[i + 1];
currMaxIndex = FindMaxPerpDistance(pts, seg, currMaxIndex);
}
}
/// <summary>
///
/// </summary>
/// <param name="seg"></param>
public void AddToResult(LineSegment seg)
{
resultSegs.Add(seg);
}
/// <summary>
///
/// </summary>
/// <param name="pts"></param>
/// <param name="seg"></param>
/// <param name="startIndex"></param>
/// <returns></returns>
private int FindMaxPerpDistance(ICoordinate[] pts, LineSegment seg, int startIndex)
{
double maxPerpDistance = seg.DistancePerpendicular(pts[startIndex]);
double nextPerpDistance = maxPerpDistance;
int maxIndex = startIndex;
int nextIndex = maxIndex;
while (nextPerpDistance >= maxPerpDistance)
{
maxPerpDistance = nextPerpDistance;
maxIndex = nextIndex;
nextIndex = NextIndex(pts, maxIndex);
nextPerpDistance = seg.DistancePerpendicular(pts[nextIndex]);
}
// found maximum width for this segment - update global min dist if appropriate
if (maxPerpDistance < minWidth)
{
minPtIndex = maxIndex;
minWidth = maxPerpDistance;
minWidthPt = pts[minPtIndex];
minBaseSeg = new LineSegment(seg);
}
return maxIndex;
}
/// <summary>
///
/// </summary>
/// <param name="querySeg"></param>
public LineSegmentVisitor(LineSegment querySeg)
{
this.querySeg = querySeg;
}
/// <summary>
///
/// </summary>
/// <param name="line0"></param>
/// <param name="line1"></param>
/// <param name="locGeom"></param>
private void ComputeMinDistance(ILineString line0, ILineString line1, GeometryLocation[] locGeom)
{
if (line0.EnvelopeInternal.Distance(line1.EnvelopeInternal) > minDistance)
return;
ICoordinate[] coord0 = line0.Coordinates;
ICoordinate[] coord1 = line1.Coordinates;
// brute force approach!
for (int i = 0; i < coord0.Length - 1; i++)
{
for (int j = 0; j < coord1.Length - 1; j++)
{
double dist = CGAlgorithms.DistanceLineLine(
coord0[i], coord0[i + 1],
coord1[j], coord1[j + 1]);
if (dist < minDistance)
{
minDistance = dist;
LineSegment seg0 = new LineSegment(coord0[i], coord0[i + 1]);
LineSegment seg1 = new LineSegment(coord1[j], coord1[j + 1]);
ICoordinate[] closestPt = seg0.ClosestPoints(seg1);
locGeom[0] = new GeometryLocation(line0, i, closestPt[0]);
locGeom[1] = new GeometryLocation(line1, j, closestPt[1]);
}
if (minDistance <= terminateDistance) return;
}
}
}
/// <summary>
///
/// </summary>
/// <param name="seg"></param>
public void Add(LineSegment seg)
{
index.Insert(new Envelope(seg.P0, seg.P1), seg);
}
/// <summary>
///
/// </summary>
/// <param name="inputPt"></param>
/// <param name="minIndex"></param>
/// <returns></returns>
private LinearLocation IndexOfFromStart(ICoordinate inputPt, LinearLocation minIndex)
{
double minDistance = Double.MaxValue;
int minComponentIndex = 0;
int minSegmentIndex = 0;
double minFrac = -1.0;
LineSegment seg = new LineSegment();
foreach (LinearIterator.LinearElement element in new LinearIterator(linearGeom))
{
if (!element.IsEndOfLine)
{
seg.P0 = element.SegmentStart;
seg.P1 = element.SegmentEnd;
double segDistance = seg.Distance(inputPt);
double segFrac = SegmentFraction(seg, inputPt);
int candidateComponentIndex = element.ComponentIndex;
int candidateSegmentIndex = element.VertexIndex;
if (segDistance < minDistance)
{
// ensure after minLocation, if any
if (minIndex == null ||
minIndex.CompareLocationValues(candidateComponentIndex, candidateSegmentIndex, segFrac) < 0)
{
// otherwise, save this as new minimum
minComponentIndex = candidateComponentIndex;
minSegmentIndex = candidateSegmentIndex;
minFrac = segFrac;
minDistance = segDistance;
}
}
}
}
LinearLocation loc = new LinearLocation(minComponentIndex, minSegmentIndex, minFrac);
return loc;
}
/// <summary>
///
/// </summary>
/// <param name="seg"></param>
public void Remove(LineSegment seg)
{
index.Remove(new Envelope(seg.P0, seg.P1), seg);
}
/// <summary>
///
/// </summary>
/// <param name="index"></param>
/// <param name="ls"></param>
public void GetLineSegment(int index, ref LineSegment ls)
{
ls.P0 = pts[index];
ls.P1 = pts[index + 1];
}
/// <summary>
/// Computes the closest points on a line segment.
/// </summary>
/// <param name="line"></param>
/// <returns>
/// A pair of Coordinates which are the closest points on the line segments.
/// </returns>
public ICoordinate[] ClosestPoints(LineSegment line)
{
// test for intersection
ICoordinate intPt = Intersection(line);
if (intPt != null)
return new ICoordinate[] { intPt, intPt };
/*
* if no intersection closest pair contains at least one endpoint.
* Test each endpoint in turn.
*/
ICoordinate[] closestPt = new ICoordinate[2];
double minDistance = Double.MaxValue;
double dist;
ICoordinate close00 = ClosestPoint(line.P0);
minDistance = close00.Distance(line.P0);
closestPt[0] = close00;
closestPt[1] = line.P0;
ICoordinate close01 = ClosestPoint(line.P1);
dist = close01.Distance(line.P1);
if (dist < minDistance)
{
minDistance = dist;
closestPt[0] = close01;
closestPt[1] = line.P1;
}
ICoordinate close10 = line.ClosestPoint(P0);
dist = close10.Distance(P0);
if (dist < minDistance)
{
minDistance = dist;
closestPt[0] = P0;
closestPt[1] = close10;
}
ICoordinate close11 = line.ClosestPoint(P1);
dist = close11.Distance(P1);
if (dist < minDistance)
{
minDistance = dist;
closestPt[0] = P1;
closestPt[1] = close11;
}
return closestPt;
}
