Engine中如何截取线上指定两点间的线段？

//调用 

IPolyline newLine = GetSubCurve(polyline, p1, p2); 



ESRI.ArcGIS.Display.IScreenDisplay screenDisplay = axMapControl1.ActiveView.ScreenDisplay; 

screenDisplay.StartDrawing(screenDisplay.hDC, System.Convert.ToInt16(ESRI.ArcGIS.Display.esriScreenCache.esriNoScreenCache)); 

IRgbColor rgbColor = new RgbColorClass(); 

rgbColor.Red = 255; 

ESRI.ArcGIS.Display.IColor color = rgbColor; // Implicit Cast 

ESRI.ArcGIS.Display.ISimpleLineSymbol simpleLineSymbol = new ESRI.ArcGIS.Display.SimpleLineSymbolClass(); 

simpleLineSymbol.Color = color; 

ESRI.ArcGIS.Display.ISymbol symbol = (ESRI.ArcGIS.Display.ISymbol)simpleLineSymbol; // Explicit Cast 

screenDisplay.SetSymbol(symbol); 

screenDisplay.DrawPolyline(newLine); 

screenDisplay.FinishDrawing(); 





private IPolyline GetSubCurve(IPolyline inpolyLine, IPoint pnt1, IPoint pnt2) 

{ 

double d1 = GetDistAlong(inpolyLine, pnt1); 

double d2 = GetDistAlong(inpolyLine, pnt2); 



var c = inpolyLine as ICurve; 

ICurve outCurve; 

c.GetSubcurve(d1, d2, false, out outCurve); 

if (c == null || c.IsEmpty) 

throw new Exception(fail); 

var outPolyline = outCurve as IPolyline; 

if (outPolyline == null) 

{ 

outPolyline = new PolylineClass() as IPolyline; 

var sc = outPolyline as ISegmentCollection; 

sc.AddSegment((ISegment)outCurve); 

((IGeometry)sc).SpatialReference = outCurve.SpatialReference; 

} 

return outPolyline; 

} 



private double GetDistAlong(IPolyline polyLine, IPoint pnt) 

{ 

var outPnt = new PointClass() as IPoint; 

double distAlong = double.NaN; 

double distFrom = double.NaN; 

bool bRight = false; 

polyLine.QueryPointAndDistance(esriSegmentExtension.esriNoExtension, pnt, false, outPnt, 

ref distAlong, ref distFrom, ref bRight); 

return distAlong; 

} 

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