计算坐标点是否在一组不规则的坐标点内

/// <summary>
/// 计算坐标点是否在一组坐标点内
/// </summary>
/// <param name="pt"></param>
/// <param name="polygon"></param>
/// <param name="noneZeroMode"></param>
/// <returns></returns>
public static bool IsWithin(Point pt, IList<Point> polygon, bool noneZeroMode)
{
int ptNum = polygon.Count();
if (ptNum < 3)
{
return false;
}
int j = ptNum - 1;
bool oddNodes = false;
int zeroState = 0;
for (int k = 0; k < ptNum; k++)
{
Point ptK = polygon[k];
Point ptJ = polygon[j];
if (((ptK.Y > pt.Y) != (ptJ.Y > pt.Y)) && (pt.X < (ptJ.X - ptK.X) * (pt.Y - ptK.Y) / (ptJ.Y - ptK.Y) + ptK.X))
{
oddNodes = !oddNodes;
if (ptK.Y > ptJ.Y)
{
zeroState++;
}
else
{
zeroState--;
}
}
j = k;
}
return noneZeroMode ? zeroState != 0 : oddNodes;
}