/// <summary> /// 获取有效的多边形 /// </summary> /// <param name="PG">多边形PG</param> /// <returns>返回多边形</returns> public static PolygonD?GetValidatePolygon(PolygonD PG) { List <PointD> pts = new List <PointD>(); for (Int32 i = 0; i < PG.Vertex.Count; ++i) { if (pts.Contains(PG.Vertex[i]) == false) { if (pts.Count > 2) { //斜率相等 if (LineAlgorithm.Gradient(new LineD(pts[pts.Count - 2], pts[pts.Count - 1])) == LineAlgorithm.Gradient(new LineD(pts[pts.Count - 1], PG.Vertex[i]))) { pts[pts.Count - 1] = PG.Vertex[i]; } else { pts.Add(PG.Vertex[i]); } } } } if (pts.Count < 3) { return(null); } return(new PolygonD(pts.ToArray())); }
/// <summary> /// 点P是否在多边形区域内 /// </summary> /// <param name="PG">多边形PL</param> /// <param name="P">点P</param> /// <returns>如果点P在区域内返回True,否则返回False.</returns> /// <remarks>此处不考虑平行边的情况</remarks> public static Boolean InPolygon(PolygonI PG, PointI P) { //count ← 0; //以P为端点,作从右向左的射线L; //for 多边形的每条边s // do if P在边s上 // then return true; // if s不是水平的 // then if s的一个端点在L上 // if 该端点是s两端点中纵坐标较大的端点 // then count ← count+1 // else if s和L相交 // then count ← count+1; //if count mod 2 = 1 // then return true; //else return false; Int32 count = 0; LineI L = new LineI(P, new PointI(Int32.MaxValue, P.Y)); foreach (LineI S in PG) { if (LineAlgorithm.OnLine(S, P) == true) { return(true); } if (LineAlgorithm.Gradient(S) != 0)//不是水平线段 { if (LineAlgorithm.OnLine(L, S.Starting) || LineAlgorithm.OnLine(L, S.End)) { if (LineAlgorithm.OnLine(L, S.Starting) && S.Starting.Y > S.End.Y) { ++count; } if (LineAlgorithm.OnLine(L, S.End) && S.End.Y > S.Starting.Y) { ++count; } } else if (LineAlgorithm.HasIntersection(S, L) > 0) { ++count; } } } //如果X的水平射线和多边形的交点数是奇数个则点在多边形内,否则不在区域内。 if (count % 2 == 0) { return(false); } return(true); }