一些常ArcGIS常用简单算法 C#

最近开始重构不顺眼的辣鸡代码，顺带将某个模块的一个算法辅助类贴到这里。

  /// <summary>
    /// 算法逻辑辅助类
    /// </summary>
    internal  static class AlgorithmHelper
    {
        /// <summary>
        /// “两点距离公式”求已知两点的距离
        /// </summary>
        /// <param name="point_start"></param>
        /// <param name="point_end"></param>
        /// <returns></returns>
        internal static double GetDistance(IPoint point_start, IPoint point_end)
        {
            double x = point_end.X - point_start.X;
            double y = point_end.Y - point_start.Y;
            double distance = Math.Sqrt(x * x + y * y);
            return distance;
        }
        /// <summary>
        /// “余弦定理”求已知三点组成的夹角的角度。
        /// </summary>
        /// <param name="first"></param>
        /// <param name="cen"></param>
        /// <param name="last"></param>
        /// <returns></returns>
        internal static double GetAngle(IPoint first, IPoint cen, IPoint last)
        {
            double ma_x = first.X - cen.X;
            double ma_y = first.Y - cen.Y;
            double mb_x = last.X - cen.X;
            double mb_y = last.Y - cen.Y;
            double ab_x = first.X - last.X;
            double ab_y = first.Y - last.Y;
            double ab_val2 = ab_x * ab_x + ab_y * ab_y;
            double ma_val = Math.Sqrt(ma_x * ma_x + ma_y * ma_y);
            double mb_val = Math.Sqrt(mb_x * mb_x + mb_y * mb_y);
            double cosM = (ma_val * ma_val + mb_val * mb_val - ab_val2) / ( * ma_val * mb_val);
            double angleAMB = Math.Acos(cosM) / System.Math.PI * ;
            return angleAMB;
        }
        /// <summary>
        /// 延长线段
        /// </summary>
        /// <param name="passLine">传入去的线</param>
        /// <param name="mode">模式，1为从FromPoint处延长，2为从ToPint处延长，3为两端延长</param>
        /// <param name="dis">延长的距离</param>
        /// <returns></returns>
        internal static IPolyline GetExtendLine(IPolyline passLine, int mode, double dis)
        {
            IPointCollection pPointCol = passLine as IPointCollection;
            switch (mode)
            {
                case :
                    IPoint fromPoint = new PointClass();
                    passLine.QueryPoint(esriSegmentExtension.esriExtendAtFrom, - * dis, false, fromPoint);
                    pPointCol.InsertPoints(, , ref fromPoint);
                    break;
                case :
                    IPoint endPoint = new PointClass();
                    object missing = Type.Missing;
                    passLine.QueryPoint(esriSegmentExtension.esriExtendAtTo, dis + passLine.Length, false, endPoint);
                    pPointCol.AddPoint(endPoint, ref missing, ref missing);
                    break;
                case :
                    IPoint fPoint = new PointClass();
                    IPoint ePoint = new PointClass();
                    object missing2 = Type.Missing;
                    passLine.QueryPoint(esriSegmentExtension.esriExtendAtFrom, - * dis, false, fPoint);
                    pPointCol.InsertPoints(, , ref fPoint);
                    passLine.QueryPoint(esriSegmentExtension.esriExtendAtTo, dis + passLine.Length, false, ePoint);
                    pPointCol.AddPoint(ePoint, ref missing2, ref missing2);
                    break;
                default:
                    return pPointCol as IPolyline;
            }
            return pPointCol as IPolyline;
        }
        /// <summary>
        /// xy坐标转地理坐标
        /// </summary>
        /// <param name="pActiveView"></param>
        /// <param name="x"></param>
        /// <param name="y"></param>
        /// <returns></returns>
        internal static IPoint XYToGeo(IActiveView pActiveView, double x, double y)
        {
            try
            {
                IMap pMap = pActiveView.FocusMap;
                IPoint pt = new PointClass();
                ISpatialReferenceFactory pfactory = new SpatialReferenceEnvironmentClass();
                ISpatialReference flatref = pMap.SpatialReference;
                ISpatialReference earthref = pfactory.CreateGeographicCoordinateSystem();
                pt.PutCoords(x, y);

                IGeometry geo = (IGeometry)pt;
                geo.SpatialReference = flatref;
                geo.Project(earthref);
                return pt;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message + "\r\n" + ex.StackTrace);
            }
        }

        /// <summary>
        /// 数字经纬度和度分秒经纬度转换
        /// </summary>
        /// <param name="digitalDegree">十进制度</param>
        /// <return>度分秒经纬度</return>
        internal static string DigitalToDegrees(double digitalDegree)
        {
            const double num = ;
            int degree = (int)digitalDegree;
            double tmp = (digitalDegree - degree) * num;
            int minute = (int)tmp;
            double second = (tmp - minute) * num;
            string degrees = "" + degree + "°" + minute + "′" + Math.Floor(second) + "″";
            return degrees;
        }
    }