public LineSegment(Point s, Point e) {
this.PtS = s;
this.PtE = e;
this.Distance = GeometryFunc.EuclideanDistanceInMeter(this.PtS, this.PtE);
this.DirAngle = GeometryFunc.ComputeAngle(this.PtS, this.PtE, true);
}
/// <summary>
/// Find the shortest distance between a point P and the line segment PtS to PtE
/// 1. Equation of line segment: PP = PtS + u(PtE-PtS); 0 leq u leq 1
/// 2. The shortest distance occured at the tangent to the line seqment which passes through P3:
// (P - PP) dot (PtE - PtS) = 0
/// 3. Solve for u by subsititude 1. into 2.
/// 4. Use u to find PP
/// 5. Find distance: distance = ||PP-P|| in meter
/// Note: meter2pixel ratios are irrelevant to find the value u.
/// </summary>
/// <param name="p"></param>
/// <param name="u">show where the tangent that depict the shortest distance lies on the line;
// closer to 0 means near PtS, vice versa</param>
public double FindShortestDist2Point(Point p, Double u) {
u =
((p.x - this.PtS.x) * (this.PtE.x - this.PtS.x)
+ (p.y - this.PtS.y) * (this.PtE.y - this.PtS.y))
/ (Math.pow(this.PtE.x - this.PtS.x, 2) + Math.pow(this.PtE.y - this.PtS.y, 2));
return GeometryFunc.EuclideanDistanceInMeter(p, this.GetPointFromEqn(u));
}
