/// <summary>
///
/// </summary>
/// <param name="c1"></param>
/// <param name="c2"></param>
/// <param name="c3"></param>
/// <returns>
/// Whether the three coordinates are collinear
/// and c2 lies between c1 and c3 inclusive.
/// </returns>
private bool IsBetween(ICoordinate c1, ICoordinate c2, ICoordinate c3)
{
if (CGAlgorithms.ComputeOrientation(c1, c2, c3) != 0)
{
return(false);
}
if (c1.X != c3.X)
{
if (c1.X <= c2.X && c2.X <= c3.X)
{
return(true);
}
if (c3.X <= c2.X && c2.X <= c1.X)
{
return(true);
}
}
if (c1.Y != c3.Y)
{
if (c1.Y <= c2.Y && c2.Y <= c3.Y)
{
return(true);
}
if (c3.Y <= c2.Y && c2.Y <= c1.Y)
{
return(true);
}
}
return(false);
}
/// <summary>
///
/// </summary>
/// <param name="o"></param>
/// <param name="p"></param>
/// <param name="q"></param>
/// <returns></returns>
private static int PolarCompare(ICoordinate o, ICoordinate p, ICoordinate q)
{
double dxp = p.X - o.X;
double dyp = p.Y - o.Y;
double dxq = q.X - o.X;
double dyq = q.Y - o.Y;
int orient = CGAlgorithms.ComputeOrientation(o, p, q);
if (orient == CGAlgorithms.CounterClockwise)
{
return(1);
}
if (orient == CGAlgorithms.Clockwise)
{
return(-1);
}
// points are collinear - check distance
double op = dxp * dxp + dyp * dyp;
double oq = dxq * dxq + dyq * dyq;
if (op < oq)
{
return(-1);
}
if (op > oq)
{
return(1);
}
return(0);
}
/// <summary>
///
/// </summary>
/// <param name="c"></param>
/// <returns></returns>
private Stack <ICoordinate> GrahamScan(ICoordinate[] c)
{
ICoordinate p;
Stack <ICoordinate> ps = new Stack <ICoordinate>(c.Length);
ps.Push(c[0]);
ps.Push(c[1]);
ps.Push(c[2]);
for (int i = 3; i < c.Length; i++)
{
p = (Coordinate)ps.Pop();
while (CGAlgorithms.ComputeOrientation((ICoordinate)ps.Peek(), p, c[i]) > 0)
{
p = (ICoordinate)ps.Pop();
}
ps.Push(p);
ps.Push(c[i]);
}
ps.Push(c[0]);
return(ps);
}
