Class VWSimplifier

Simplifies a Geometry using the Visvalingam-Whyatt area-based algorithm. Ensures that any polygonal geometries returned are valid. Simple lines are not guaranteed to remain simple after simplification. All geometry types are handled. Empty and point geometries are returned unchanged. Empty geometry components are deleted. The simplification tolerance is specified as a distance. This is converted to an area tolerance by squaring it.

Known Bugs * Not yet optimized for performance. * Does not simplify the endpoint of rings. To Do * Allow specifying desired number of vertices in the output.

Inheritance

object

VWSimplifier

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: NetTopologySuite.Simplify

Assembly: NetTopologySuite.dll

Syntax

public class VWSimplifier

Remarks

Note that in general this algorithm does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross.

Constructors

VWSimplifier(Geometry)

Creates a simplifier for a given Geometry.

Declaration

public VWSimplifier(Geometry inputGeom)

Parameters

Type	Name	Description
Geometry	inputGeom	The Geometry to simplify.

Properties

DistanceTolerance

Sets the distance tolerance for the simplification. All vertices in the simplified Geometry will be within this distance of the original geometry. The tolerance value must be non-negative.

Declaration

public double DistanceTolerance { get; set; }

Property Value

Type	Description
double

IsEnsureValidTopology

Controls whether simplified polygons will be "fixed" to have valid topology. The caller may choose to disable this because:

• valid topology is not required.
• fixing topology is a relative expensive operation.
• in some pathological cases the topology fixing operation may either fail or run for too long.

Declaration

public bool IsEnsureValidTopology { get; set; }

Property Value

Type	Description
bool

Remarks

The default is to fix polygon topology.

Methods

GetResultGeometry()

Gets the simplified Geometry.

Declaration

public Geometry GetResultGeometry()

Returns

Type	Description
Geometry	The simplified Geometry.

Simplify(Geometry, double)

Simplifies a Geometry using a given tolerance.

Declaration

public static Geometry Simplify(Geometry geom, double distanceTolerance)

Parameters

Type	Name	Description
Geometry	geom	The Geometry to simplify.
double	distanceTolerance	The tolerance to use.

Returns

Type	Description
Geometry	A simplified version of the Geometry.