It provides an easy way of applying specific transformations to given point types, while allowing unhandled types to be simply copied. Also, the framework handles ensuring that if subcomponents change type the parent geometries types change appropriately to maintain valid structure. Subclasses will override whichever TransformX methods they need to to handle particular Geometry types.

A typically usage would be a transformation that may transform Polygons into Polygons, LineStrings or Points, depending on the geometry of the input (For instance, a simplification operation). This class would likely need to override the TransformMultiPolygon(MultiPolygon, Geometry) method to ensure that if input Polygons change type the result is a GeometryCollection, not a MultiPolygon.

The default behaviour of this class is simply to recursively transform each Geometry component into an identical object by deep copying down to the level of, but not including, coordinates.

Note that all TransformXXX methods may return null, to avoid creating empty point objects. This will be handled correctly by the transformer. TransformXXX methods should always return valid geometry - if they cannot do this they should return null (for instance, it may not be possible for a transformLineString implementation to return at least two points - in this case, it should return null). The Transform(Geometry) method itself will always return a non-null Geometry object (but this may be empty).

Fields

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Factory

The geometry factory

Declaration

protected GeometryFactory Factory

Field Value

Type	Description
GeometryFactory

Properties

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InputGeometry

Makes the input geometry available

Declaration

public Geometry InputGeometry { get; }

Property Value

Type	Description
Geometry

Methods

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Copy(CoordinateSequence)

Convenience method which provides a standard way of copying CoordinateSequences.

Declaration

protected virtual CoordinateSequence Copy(CoordinateSequence seq)

Parameters

Type	Name	Description
CoordinateSequence	seq	The sequence to copy.

Returns

Type	Description
CoordinateSequence	A deep copy of the sequence.

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CreateCoordinateSequence(Coordinate[])

Convenience method which provides standard way of creating a CoordinateSequence.

Declaration

protected virtual CoordinateSequence CreateCoordinateSequence(Coordinate[] coords)

Parameters

Type	Name	Description
Coordinate[]	coords	The coordinate array to copy.

Returns

Type	Description
CoordinateSequence	A coordinate sequence for the array.

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Transform(Geometry)

Declaration

public Geometry Transform(Geometry inputGeom)

Parameters

Type	Name	Description
Geometry	inputGeom

Returns

Type	Description
Geometry

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TransformCoordinates(CoordinateSequence, Geometry)

Transforms a CoordinateSequence. This method should always return a valid coordinate list for the desired result type. (E.g. a coordinate list for a LineString must have 0 or at least 2 points). If this is not possible, return an empty sequence - this will be pruned out.

Declaration

protected virtual CoordinateSequence TransformCoordinates(CoordinateSequence coords, Geometry parent)

Parameters

Type	Name	Description
CoordinateSequence	coords	The coordinates to transform
Geometry	parent	The parent geometry

Returns

Type	Description
CoordinateSequence	The transformed coordinates

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TransformGeometryCollection(GeometryCollection, Geometry)

Transforms a GeometryCollection geometry.

Declaration

protected virtual Geometry TransformGeometryCollection(GeometryCollection geom, Geometry parent)

Parameters

Type	Name	Description
GeometryCollection	geom	The `GeometryCollection` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `GeometryCollection`

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TransformLinearRing(LinearRing, Geometry)

Transforms a LinearRing.

The transformation of a LinearRing may result in a coordinate sequence which does not form a structurally valid ring (i.e. a degenerate ring of 3 or fewer points). In this case a LineString is returned. Subclasses may wish to override this method and check for this situation (e.g.a subclass may choose to eliminate degenerate linear rings)

Declaration

protected virtual Geometry TransformLinearRing(LinearRing geom, Geometry parent)

Parameters

Type	Name	Description
LinearRing	geom	The `LinearRing` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `LinearRing` if the transformation resulted in a structurally valid ring, otherwise, if the transformation caused the LinearRing to collapse to 3 or fewer points, a `LineString`

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TransformLineString(LineString, Geometry)

Transforms a LineString geometry.

Declaration

protected virtual Geometry TransformLineString(LineString geom, Geometry parent)

Parameters

Type	Name	Description
LineString	geom	The `LineString` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `LineString`

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TransformMultiLineString(MultiLineString, Geometry)

Transforms a MultiLineString geometry.

Declaration

protected virtual Geometry TransformMultiLineString(MultiLineString geom, Geometry parent)

Parameters

Type	Name	Description
MultiLineString	geom	The `MultiLineString` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `MultiLineString`

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TransformMultiPoint(MultiPoint, Geometry)

Transforms a MultiPoint geometry.

Declaration

protected virtual Geometry TransformMultiPoint(MultiPoint geom, Geometry parent)

Parameters

Type	Name	Description
MultiPoint	geom	The `MultiPoint` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `MultiPoint`

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TransformMultiPolygon(MultiPolygon, Geometry)

Transforms a MultiPolygon geometry.

Declaration

protected virtual Geometry TransformMultiPolygon(MultiPolygon geom, Geometry parent)

Parameters

Type	Name	Description
MultiPolygon	geom	The `MultiPolygon` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `MultiPolygon`

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TransformPoint(Point, Geometry)

Transforms a Point geometry.

Declaration

protected virtual Geometry TransformPoint(Point geom, Geometry parent)

Parameters

Type	Name	Description
Point	geom	The `Point` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `Point`

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TransformPolygon(Polygon, Geometry)

Transforms a Polygon geometry.

Declaration

protected virtual Geometry TransformPolygon(Polygon geom, Geometry parent)

Parameters

Type	Name	Description
Polygon	geom	The `Polygon` to transform
Geometry	parent	The parent geometry

Returns

Type	Description
Geometry	A `Polygon`