[求助]缓冲区分析

在缓冲区分析中有三种方法，其中属性权值缓冲区（以分析对象的属性值作为权值建立缓冲区），分级缓冲区（建立一个给定环个数和间距的分级缓冲区）怎么在vc中实现，函数是怎样的？

<P>Sub exampleITopologicalOperator_Buffer()<BR>Dim ptc As IPointCollection, i As Long, pa As IArea, ptopo As ITopologicalOperator<BR>Dim pt(4) As IPoint, poutPoly As IPolygon<BR>Set ptc = New Polygon<BR>'The spatial reference should be set here using IGeometry::SpatialReference (Code skipped here)<BR>For i = 0 To 4<BR>   Set pt(i) = New Point<BR>Next<BR>pt(0).PutCoords 0, 0<BR>pt(1).PutCoords 0, 10<BR>pt(2).PutCoords 10, 10<BR>pt(3).PutCoords 10, 0<BR>pt(4).PutCoords 0, 0<BR>ptc.AddPoints 5, pt(0)<BR>Set pa = ptc<BR>Debug.Print "Area original polygon : " ; pa.Area<BR>Set ptopo = ptc<BR>Set poutPoly = ptopo.Buffer(1) 'Outside buffer<BR>Set pa = poutPoly<BR>Debug.Print "Area polygon positive distance : " ; pa.Area<BR>Set poutPoly = ptopo.Buffer(-1) 'Inside buffer<BR>Set pa = poutPoly<BR>Debug.Print "Area polygon negative distance : " ; pa.Area<BR>End Sub</P>