public static Point PolygonCentre(IPolygonReader poly)
{
if (poly == null)
{
throw (new ArgumentNullException("PolygonCentre(poly)"));
}
Point ret = new Point();
double[] v = new double[3] {
0, 0, 0
};
double[,] p = poly.CopyTo();
double dx, dy;
int b = p.GetLength(0) - 1;
for (int e = 0; e < p.GetLength(0); e++)
{
dx = p[e, 0] - p[b, 0];
dy = p[e, 1] - p[b, 1];
v[2] += (p[b, 0] * dy - p[b, 1] * dx) / 2.0;
v[0] += -dx * (3.0 * p[b, 1] * p[b, 1] + 3.0 * p[b, 1] * dy + dy * dy) / 6.0;
v[1] += dy * (3.0 * p[b, 0] * p[b, 0] + 3.0 * p[b, 0] * dx + dx * dx) / 6.0;
b = e;
}
ret.X = v[1] / v[2];
ret.Y = v[0] / v[2];
return(ret);
}
public PolygonSelfCrossing(IPolygonReader poly, bool isClosed = true)
{
IsClosed = isClosed;
if (poly == null)
{
throw (new ArgumentNullException("PolygonSelfCrossing(poly)"));
}
myCrossId = null;
mySplits = null;
myPoly = poly.CopyTo();
int length = myPoly.GetLength(0);
myData = new MyLine[length];
for (int i = 0; i < myData.Length; i++)
{
myData[i] = new MyLine(i, i == (myData.Length - 1));
}
int begin = 0;
if (!IsClosed)
{
length -= 2;
begin = 1;
}
for (int i = begin; i < length; i++)
{
for (int j = i + 2; j < length; j++)
{
if (myData[i].TestCrossing(myData[j], myPoly))
{
if (myCrossId == null)
{
myCrossId = new List <int[]>();
}
myCrossId.Add(new int[] { i, j });
}
}
}
for (int i = 0; i < myData.Length; i++)
{
myData[i].Sort();
}
}
// vrati relativni souradnice pruseciku primky s polygonem
public static List <double> PolygonLineCrossingRel(IPolygonReader poly, bool closed, Point pt, Vector v)
{
if (poly == null)
{
throw (new ArgumentNullException("PolygonLineCrossing_rel(poly,..)"));
}
List <double> ret = new List <double>();
int b, e;
double[,] p = poly.CopyTo();
if (closed)
{
e = poly.Length - 1;
b = 0;
}
else
{
e = 0;
b = 1;
}
Point p1, p2;
for (int i = b; i < poly.Length; i++)
{
b = e; e = i;
p1 = new Point(p[b, 0], p[b, 1]);
p2 = new Point(p[e, 0], p[e, 1]);
if (TwoLine2D.CrossRel(pt, v, p1, p2.Minus(p1), out Point pr))
{
if (TwoLine2D.TestRelOnLine(TwoLine2D.CrossStatus.And, pr.Y))
{
ret.Add(pr.X);
}
}
}
ret.Sort();
return(ret);
}
// polygons
private static double f_PolygonArea(IPolygonReader poly)
{
if (poly == null)
{
throw (new ArgumentNullException("f_PolygonArea(poly)"));
}
if (poly.Length < 3)
{
return(0);
}
double dx, dy, a = 0;
double[,] p = poly.CopyTo();
int b = p.GetLength(0) - 1;
for (int e = 0; e < p.GetLength(0); e++)
{
dx = p[e, 0] - p[b, 0];
dy = p[e, 1] - p[b, 1];
a += (p[b, 0] * dy - p[b, 1] * dx) / 2.0;
b = e;
}
return(a);
}