public MBR GetMBR()
{
double minX = 99999999999;
double minY = 99999999999;
double maxX = -99999999999;
double maxY = -99999999999;
MBR mbr = new MBR();
foreach (var ring in LinearRings)
{
foreach (var p in ring)
{
if (p.X < minX)
{
minX = p.X;
}
if (p.Y < minY)
{
minY = p.Y;
}
if (p.X > maxX)
{
maxX = p.X;
}
if (p.Y > maxY)
{
maxY = p.Y;
}
}
}
mbr.Southwest = new Point(minX, minY);
mbr.Northeast = new Point(maxX, maxY);
return(mbr);
}
/// <summary>
/// Uses the raycasting algorithm
/// </summary>
/// <param name="p"></param>
/// <returns></returns>
public bool ContainsPoint(Point p)
{
//the point must at least be in the bounding box to continue below
MBR mbr = this.GetMBR();
if (!mbr.ContainsPoint(p))
{
return(false);
}
#region Partial Differential Equation Theory or simple line
//---Line intersection
/*
* Lets consider 2 lines
* Y = X + 1
* Y = -5X -2
*
* To see if they intersect lets set them equal to each other
* X + 1 = -5X - 2
*
* Solve for X
*
* 6X = -3
* X = -1/2
*
* Plug back into original equations
*
* Y = 1/2
*
* These lines cross at (-1/2, 1/2)
*/
//---Finding the intercept
/*
* Equation of a line --> Y = mX + b
*
* m = (Y2 - Y1) / (X2 - X1)
*
* b = Y - mX
*
* Lets consider the 2 points
* (1, 3) and (2,5)
*
* m = 2
*
* b = 3 - 2(1) = 1
*
* Line --> Y = 2X + 1
*/
#endregion
Point rayEnd = new Point(p.X + 1000000, p.Y);
LineSegment ray = new LineSegment(p, rayEnd);
int crossCount = 0;
bool itDoes = false;
foreach (List <Point> ring in this.LinearRings)
{
for (int i = 0; i < ring.Count - 1; i++)
{
Point current = ring[i];
Point next = ring[i + 1];
LineSegment segment = new LineSegment(current, next);
//--does the "segment" intersect the "ray"
if (segment.Intersects(ray))
{
++crossCount;
itDoes = !itDoes;
}
}
}
return(itDoes);
}
