ArcObjects Library Reference (Geometry)

ITopologicalOperator.Buffer Method

Constructs a polygon that is the locus of points at a distance less than or equal to a specified distance from this geometry.

[Visual Basic .NET]
Public Function Buffer ( _
    ByVal distance As Double _
) As IGeometry

[C#]
public IGeometry Buffer (
    double distance
);

[C++]
HRESULT Buffer(
  double distance,
  IGeometry** outBuffer
);

[C++]
Parameters
distance 
  distance is a parameter of type double
outBuffer [out, retval]
  outBuffer is a parameter of type IGeometry

Product Availability

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

Remarks

The buffer distance is in the same units as the source shape that is being buffered.

A negative distance can be specified to produce a buffer inside the original polygon. This cannot be used with polyline. ITopologicalOperator methods must be applied on top-level geometries only. Top-Level geometries are point, multipoint, polyline and polygon. To use this method with segments (Line, Circular Arc, Elliptic Arc, Bézier Curve), paths or rings, they must be wrapped with a top-level type.

Buffer Example

[C#]

//The following code shows to wrap a line segment into a polyline in C#

//Assume a line (line1 as ILine) is already created

object obj = Type.Missing;

ISegmentCollection segCollection = new PolylineClass() as ISegmentCollection;

segCollection.AddSegment((ISegment)line1, ref obj, ref obj);

//Set the spatial reference on the new polyline

//The spatial reference is not transfered automatically from the segments

IGeometry geom = segCollection as IGeometry;

geom.SpatialReference = spatialRef;

//Can now be used with ITopologicalOperator methods

[C#]//This example demonstrates how to use ITopologicalOperator::Buffer
private void BufferArea()
{
IPoint[] points = new IPoint[5];
//The spatial reference should be set here using IGeometry::SpatialReference (Code skipped here)
for(int i = 0; i < points.Length; i++)
{
points[i] = new PointClass();
}
points[0].PutCoords(0, 0);
points[1].PutCoords(0, 10);
points[2].PutCoords(10, 10);
points[3].PutCoords(10, 0);
points[4].PutCoords(0, 0);
IPointCollection4 pointCollection = new PolygonClass();
IGeometryBridge geometryBride = new GeometryEnvironmentClass();
geometryBride.AddPoints(pointCollection, ref points);
IArea area = pointCollection as IArea;
System.Windows.Forms.MessageBox.Show("Area original polygon : " + area.Area);
ITopologicalOperator topologicalOperator = pointCollection as ITopologicalOperator;
//Outside buffer
IPolygon polygon = topologicalOperator.Buffer(1) as IPolygon;
area = polygon as IArea;
System.Windows.Forms.MessageBox.Show( "Area polygon positive distance : " + area.Area);
//Inside buffer
polygon = topologicalOperator.Buffer(-1) as IPolygon;
area = polygon as IArea;
System.Windows.Forms.MessageBox.Show("Area polygon negative distance : " + area.Area);
}

[Visual Basic .NET]

    Sub exampleITopologicalOperator_Buffer()
        Dim ptc As ESRI.ArcGIS.Geometry.IPointCollection, i As Long, pa As ESRI.ArcGIS.Geometry.IArea, ptopo As ESRI.ArcGIS.Geometry.ITopologicalOperator
        ptc = New ESRI.ArcGIS.Geometry.Polygon
        Dim pt(4) As ESRI.ArcGIS.Geometry.IPoint, poutPoly As ESRI.ArcGIS.Geometry.IPolygon
        'The spatial reference should be set here using IGeometry::SpatialReference (Code skipped here)
        For i = 0 To 4
            pt(i) = New ESRI.ArcGIS.Geometry.Point
        Next
        pt(0).PutCoords(0, 0)
        pt(1).PutCoords(0, 10)
        pt(2).PutCoords(10, 10)
        pt(3).PutCoords(10, 0)
        pt(4).PutCoords(0, 0)
        Dim geometryBride As ESRI.ArcGIS.Geometry.IGeometryBridge
        geometryBride = New ESRI.ArcGIS.Geometry.GeometryEnvironmentClass()
        geometryBride.AddPoints(ptc, pt)
        pa = ptc
        Debug.Print("Area original polygon : " & pa.Area)
        ptopo = ptc
        poutPoly = ptopo.Buffer(1) 'Outside buffer
        pa = poutPoly
        Debug.Print("Area polygon positive distance : " & pa.Area)
        poutPoly = ptopo.Buffer(-1) 'Inside buffer
        pa = poutPoly
        Debug.Print("Area polygon negative distance : " & pa.Area)
    End Sub

ITopologicalOperator.Buffer Method

Product Availability

Remarks

See Also