Polylines to a Polygon Feature Class

8/3/2019 Polylines to a Polygon Feature Class

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The code below takes the closed Polylines from an existing FeatureClass, and creates a new

FeatureClass of Polygons from them. The FeatureClass must be in a GeoDatabase

FeatureDataset - the new FeatureClass is created in this FeatureDataset.

How to use:

1. Open ArcMap, open the VBA editor and paste the code below into the code window.2. Add a FeatureDataset containing a Polyline FeatureClass. Some of the Polyline

features should form closed loops.

3. Run the ClosedLinesNewFC macro.Public Sub ClosedLinesNewFC()

'

' Get the current map.

'

Dim pMxDoc As IMxDocument, pMap As IMap

Set pMxDoc = ThisDocument

Set pMap = pMxDoc.FocusMap'

' Here, we select the top layer in the Map to work with.

'

Dim pFeatureLyr As IFeatureLayer, pFeatureClass As IFeatureClass

If TypeOf pMap.Layer(0) Is IFeatureLayer Then

Set pFeatureLyr = pMap.Layer(0)

Set pFeatureClass = pFeatureLyr.FeatureClass

'

' Check the layer belongs to a (Local or Remote) GeoDatabase

FeatureDataset - we will

' add the new FeatureClass of Polygons to this same FeatureDataset.

'

If Not pFeatureClass.FeatureDataset Is Nothing ThenDim pFeatureDataset As IFeatureDataset

Set pFeatureDataset = pFeatureClass.FeatureDataset

If Not pFeatureDataset.Workspace.Type = esriFileSystemWorkspace Then

'

' Check we have some closed lines before going ahead and creating a

FeatureClass.

'

If fnHasClosedLines(pFeatureClass) Then

'

' If we have found some closed lines, then create a FeatureClass.

The first step

' is to establish a fields collection, by copying the existing

Fields collection,' and altering the GeometryDef to contain Polygons instead of

Polylines.

'

Dim pNewFields As IFields

Set pNewFields = fnMakePolygonFields(pFeatureClass.Fields,

pFeatureClass.ShapeFieldName)

If pNewFields Is Nothing Then Exit Sub

If Not pNewFields.FieldCount = pFeatureClass.Fields.FieldCount

Then Exit Sub

'

' Create the new FeatureClass in the FeatureDataset, using the

cloned and edited

' Fields collection, and the name NewPolygons.'

Dim pNewFeatureClass As IFeatureClass


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Set pNewFeatureClass =

pFeatureDataset.CreateFeatureClass("NewPolygons", pNewFields, Nothing,

Nothing, esriFTSimple, pFeatureClass.ShapeFieldName, "")

'

' Start editing the FeatureClass we have created.

'

Dim pNewDataset As IDataset, pNewWorkspaceEdit As IWorkspaceEditSet pNewDataset = pNewFeatureClass

Set pNewWorkspaceEdit = pNewDataset.Workspace

pNewWorkspaceEdit.StartEditing False

pNewWorkspaceEdit.StartEditOperation

'

' Now we create a FeatureCursor from all of the features in the

original feature

' class. We use this cursor to iterate the features to find

closed Polylines.

'

Dim pFeatureCursor As IFeatureCursor, pFeature As IFeature

Set pFeatureCursor = pFeatureClass.Search(Nothing, False)

Set pFeature = pFeatureCursor.NextFeature

Dim pCurve As ICurve

Do While Not pFeature Is Nothing

Set pCurve = pFeature.Shape

If fnCurveClosed(pCurve) Then

'

' Add the closed line to the new FeatureClass as a Polygon,

copying the attributes.

'

Dim pPolygon As IPolygon

Set pPolygon = fnPolylineToPolygon(pCurve)

Dim pNewFeature As IFeature

Set pNewFeature = pNewFeatureClass.CreateFeature

'

' Iterate all the Fields to copy the attribute values.

'

Dim i As Integer

For i = 0 To pNewFields.FieldCount - 1

If (Not pNewFields.Field(i).Type = esriFieldTypeGeometry)

And (Not pNewFields.Field(i).Type = esriFieldTypeOID) Then

If pNewFields.Field(i).Editable Then

pNewFeature.Value(i) = pFeature.Value(i)

End If

End If

Next i

Set pNewFeature.Shape = pPolygon

pNewFeature.Store

End If

'

' Get the next Feature in the original Polyline FeatureClass.

'


Loop

'

' After iterating all of the features, stop the editing operation

and

' save the edits made.

'

pNewWorkspaceEdit.StopEditOperation

pNewWorkspaceEdit.StopEditing True


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'

' Add the new FeatureClass to the Map as a layer.

'

Dim pNewFeatureLayer As IFeatureLayer

Set pNewFeatureLayer = New FeatureLayer

Set pNewFeatureLayer.FeatureClass = pNewFeatureClass

pNewFeatureLayer.Name = pNewFeatureClass.AliasNamepMap.AddLayer pNewFeatureLayer

End If

End If

Else

MsgBox "To use this sample, your data should be part of a GeoDatabase

FeatureDataset." _

& vbNewLine & "You can create a FeatureDataset within ArcCatalog",

vbInformation

End If

End If

End Sub

Private Function fnMakePolygonFields(ByVal pOldFields As IFields,strShapeFieldName As String) As IFields

'

' This function creates a new Fields collection from an existing object,

' but changes the Geometry type held to Polylines. We pass in the

existing

' Fields collection by value to avoid changing the existing Fields.

'

If Not pOldFields Is Nothing Then

Set fnMakePolygonFields = pOldFields

Dim pFieldsEdit As esriCore.IFieldsEdit

Dim pFieldEdit As IFieldEdit, pField As IField

Dim pGeomDef As IGeometryDef, pGeomDefEdit As IGeometryDefEdit, lGeom

As Long

'

' Find the Field containing the shapes.

'

lGeom = fnMakePolygonFields.FindField(strShapeFieldName)

Set pField = fnMakePolygonFields.Field(lGeom)

Set pFieldEdit = pField

'

' Copy the current GeometryDefinition, get the GeometryDef editing

interface,

' and change it to store Polygons.

'

Set pGeomDef = pField.GeometryDef

Set pGeomDefEdit = pGeomDef

pGeomDefEdit.GeometryType = esriGeometryPolygon

'

' Set the new GeometryDef back to the Shape field.

'

With pFieldEdit

.Name = strShapeFieldName

.Type = esriFieldTypeGeometry

Set .GeometryDef = pGeomDef

End With

Set pFieldsEdit = fnMakePolygonFields

Set pFieldsEdit.Field(lGeom) = pFieldEdit

End If

End Function


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Private Function fnHasClosedLines(pFeatClass As IFeatureClass) As Boolean

fnHasClosedLines = False

If Not pFeatClass.ShapeType = esriGeometryPolyline Then Exit Function

'

' Check each feature in the FeatureClass to see if any features can be

classed as

' closed. We could use the ICurve.IsClosed property, but this way we canallow

' for a small tolerance in the distance between the FromPoint and

ToPoint.

'

Dim pFeatureCursor As IFeatureCursor, pFeature As IFeature

Set pFeatureCursor = pFeatClass.Search(Nothing, False)


'

' Iterate all Features.

'

Do While Not pFeature Is Nothing

If fnCurveClosed(pFeature.Shape) Then

fnHasClosedLines = TrueExit Function

End If


Loop

End Function

Private Function fnCurveClosed(pCurve As ICurve) As Boolean

fnCurveClosed = False

'

' We use the IProximityOperator interface to work out the distance

between

' the FromPoint and ToPoint of the curve passed in.

'

Dim pProxOp As IProximityOperator, dblDist As Double

Set pProxOp = pCurve.FromPoint

dblDist = pProxOp.ReturnDistance(pCurve.ToPoint)

'

' This is our tolerance for a 'closed' curve. We could relate this to a

snapping

' tolerance, or to the spatial reference, or to the size of the shape,

instead

' of hardcoding the distance.

'

If (dblDist < 0.0001) Then fnCurveClosed = True

End Function

Private Function fnPolylineToPolygon(ByVal pPolyline As IPolyline) As

IPolygon

'

' This function converts a Polyline to a Polygon, by creating a new

Polygon

' object and copying the Segments from the Polyline to the new Polygon,

and

' then ensuring the Polygon is Simple.

'

Set fnPolylineToPolygon = New Polygon

'

' Passing the Polyline by value means that we do not need to clone the

Polyline.

'


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Dim pPolygonSegs As ISegmentCollection, pPolylineSegs As

ISegmentCollection

Set pPolygonSegs = fnPolylineToPolygon

Set pPolylineSegs = pPolyline

'

' Here we copy the Segment objects by using the QuerySegments and

AddSegments' methods on the ISegmentCollection interface, which is implemented by

both

' a Polygon and Polyline coclass.

'

Dim pSegs() As ISegment

ReDim pSegs(pPolylineSegs.SegmentCount - 1) As ISegment

pPolylineSegs.QuerySegments 0, pPolylineSegs.SegmentCount, pSegs(0)

If UBound(pSegs) > 0 Then

pPolygonSegs.AddSegments UBound(pSegs) + 1, pSegs(0)

End If

'

' The Polygon may have it's rings oriented incorrectly, or have

overlapping Rings.' We call simplify here to ensure the new Polygon is Simple, which is a

requirement

' for adding to a FeatureClass.

'

fnPolylineToPolygon.SimplifyPreserveFromTo

End Function

Documents

Polylines to a Polygon Feature Class