public class PositionAlgorithmHelper{/// <summary>/// 判断当前位置是否在不规则形状里面/// </summary>/// <param name="nvert">不规则形状的定点数</param>/// <param name="vertx">当前x坐标</param>/// <param name="verty">当前y坐标</param>/// <param name="testx">不规则形状x坐标集合</param>/// <param name="testy">不规则形状y坐标集合</param>/// <returns></returns>public static bool PositionPnpoly(int nvert, List<double> vertx, List<double> verty, double testx, double testy){int i, j, c = 0;for (i = 0, j = nvert - 1; i < nvert; j = i++){if (((verty[i] > testy) != (verty[j] > testy)) && (testx < (vertx[j] - vertx[i]) * (testy - verty[i]) / (verty[j] - verty[i]) + vertx[i])){c = 1 + c; ;}}if (c % 2 == 0){return false;}else{return true;}}}

class Program{static void Main(string[] args){test1();}/// <summary>/// test1/// </summary>public static void test1(){//不规则图像坐标List<Position> position = new List<Position>();position.Add(new Position() { x = 6, y = 0 });position.Add(new Position() { x = 10, y = 2 });position.Add(new Position() { x = 16, y = 2 });position.Add(new Position() { x = 20, y = 6 });position.Add(new Position() { x = 14, y = 10 });position.Add(new Position() { x = 16, y = 6 });position.Add(new Position() { x = 12, y = 6 });position.Add(new Position() { x = 14, y = 8 });position.Add(new Position() { x = 10, y = 8 });position.Add(new Position() { x = 8, y = 6 });position.Add(new Position() { x = 12, y = 4 });position.Add(new Position() { x = 6, y = 4 });position.Add(new Position() { x = 8, y = 2 });//用户当前位置坐标List<Position> userPositions = new List<Position>();userPositions.Add(new Position() { x = 14, y = 4 });userPositions.Add(new Position() { x = 15, y = 4 });userPositions.Add(new Position() { x = 10, y = 6 });userPositions.Add(new Position() { x = 8, y = 5 });//不规则图像x坐标集合List<double> xList = position.Select(x => x.x).ToList();//不规则图像y坐标集合List<double> yList = position.Select(x => x.y).ToList();foreach (var userPosition in userPositions){bool result = PositionAlgorithmHelper.PositionPnpoly(position.Count, xList, yList, userPosition.x, userPosition.y);if (result){Console.WriteLine(string.Format("{0},{1}【在】坐标内", userPosition.x, userPosition.y));}else{Console.WriteLine(string.Format("{0},{1}【不在】坐标内", userPosition.x, userPosition.y));}}}}

/// <summary>  /// 判断点是否在多边形内.  /// ----------原理----------  /// 注意到如果从P作水平向左的射线的话，如果P在多边形内部，那么这条射线与多边形的交点必为奇数，  /// 如果P在多边形外部，则交点个数必为偶数(0也在内)。  /// 所以，我们可以顺序考虑多边形的每条边，求出交点的总个数。还有一些特殊情况要考虑。假如考虑边(P1,P2)，  /// 1)如果射线正好穿过P1或者P2,那么这个交点会被算作2次，处理办法是如果P的从坐标与P1,P2中较小的纵坐标相同，则直接忽略这种情况  /// 2)如果射线水平，则射线要么与其无交点，要么有无数个，这种情况也直接忽略。  /// 3)如果射线竖直，而P0的横坐标小于P1,P2的横坐标，则必然相交。  /// 4)再判断相交之前，先判断P是否在边(P1,P2)的上面，如果在，则直接得出结论：P再多边形内部。  /// </summary>  /// <param name="checkPoint">要判断的点</param>  /// <param name="polygonPoints">多边形的顶点</param>  /// <returns></returns>  public static bool IsInPolygon2(Position checkPoint, List<Position> polygonPoints){int counter = 0;int i;double xinters;Position p1, p2;int pointCount = polygonPoints.Count;p1 = polygonPoints[0];for (i = 1; i <= pointCount; i++){p2 = polygonPoints[i % pointCount];if (checkPoint.y > Math.Min(p1.y, p2.y)//校验点的Y大于线段端点的最小Y  && checkPoint.y <= Math.Max(p1.y, p2.y))//校验点的Y小于线段端点的最大Y  {if (checkPoint.x <= Math.Max(p1.x, p2.x))//校验点的X小于等线段端点的最大X(使用校验点的左射线判断).  {if (p1.y != p2.y)//线段不平行于X轴  {xinters = (checkPoint.y - p1.y) * (p2.x - p1.x) / (p2.y - p1.y) + p1.x;if (p1.x == p2.x || checkPoint.x <= xinters){counter++;}}}}p1 = p2;}if (counter % 2 == 0){return false;}else{return true;}}/// <summary>  /// 判断点是否在多边形内.  /// ----------原理----------  /// 注意到如果从P作水平向左的射线的话，如果P在多边形内部，那么这条射线与多边形的交点必为奇数，  /// 如果P在多边形外部，则交点个数必为偶数(0也在内)。  /// </summary>  /// <param name="checkPoint">要判断的点</param>  /// <param name="polygonPoints">多边形的顶点</param>  /// <returns></returns>  public static bool IsInPolygon(Position checkPoint, List<Position> polygonPoints){bool inside = false;int pointCount = polygonPoints.Count;Position p1, p2;for (int i = 0, j = pointCount - 1; i < pointCount; j = i, i++)//第一个点和最后一个点作为第一条线，之后是第一个点和第二个点作为第二条线，之后是第二个点与第三个点，第三个点与第四个点...  {p1 = polygonPoints[i];p2 = polygonPoints[j];if (checkPoint.y < p2.y){//p2在射线之上  if (p1.y <= checkPoint.y){//p1正好在射线中或者射线下方  if ((checkPoint.y - p1.y) * (p2.x - p1.x) > (checkPoint.x - p1.x) * (p2.y - p1.y))//斜率判断,在P1和P2之间且在P1P2右侧  {//射线与多边形交点为奇数时则在多边形之内，若为偶数个交点时则在多边形之外。  //由于inside初始值为false，即交点数为零。所以当有第一个交点时，则必为奇数，则在内部，此时为inside=(!inside)  //所以当有第二个交点时，则必为偶数，则在外部，此时为inside=(!inside)  inside = (!inside);}}}else if (checkPoint.y < p1.y){//p2正好在射线中或者在射线下方，p1在射线上  if ((checkPoint.y - p1.y) * (p2.x - p1.x) < (checkPoint.x - p1.x) * (p2.y - p1.y))//斜率判断,在P1和P2之间且在P1P2右侧  {inside = (!inside);}}}return inside;}