Class GeometryPrecisionReducer

Namespace

NetTopologySuite.Precision

Assembly

NetTopologySuite.dll

Reduces the precision of a Geometry according to the supplied PrecisionModel, ensuring that the result is valid (unless specified otherwise).

By default the geometry precision model is not changed. This can be overridden by using ChangePrecisionModel.

Topological Precision Reduction

The default mode of operation ensures the reduced result is topologically valid (i.e. IsValid is true). To ensure this polygonal geometry is reduced in a topologically valid fashion (technically, by using snap-rounding). Note that this may change polygonal geometry structure (e.g.two polygons separated by a distance below the specified precision will be merged into a single polygon). Duplicate vertices are removed. This mode is invoked by the static method Reduce(Geometry, PrecisionModel).

Normally, collapsed linear components(e.g.lines collapsing to a point) are not included in the result. This behavior can be changed by setting RemoveCollapsedComponents to false, or by using the static method ReduceKeepCollapsed(Geometry, PrecisionModel).

In general input must be valid geometry, or an ArgumentException will be thrown. However if the invalidity is "mild" or very small then it may be eliminated by precision reduction.

Pointwise Precision Reduction

Alternatively, geometry can be reduced pointwise by using {@link #setPointwise(boolean)}. Linear and point geometry are always reduced pointwise(i.e.without further change to topology or structure), since this does not change validity. Invalid inputs are allowed. Duplicate vertices are preserved. Collapsed components are always included in the result. The result geometry may be invalid.

This mode is invoked by the static method ReducePointwise(Geometry, PrecisionModel).

public class GeometryPrecisionReducer

Inheritance

object

GeometryPrecisionReducer

Inherited Members

object.GetType()

object.MemberwiseClone()

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

Constructors

GeometryPrecisionReducer(PrecisionModel)

public GeometryPrecisionReducer(PrecisionModel pm)

Parameters

pm PrecisionModel

Properties

ChangePrecisionModel

Gets or sets whether the PrecisionModel of the new reduced Geometry will be changed to be the PrecisionModel supplied to specify the precision reduction.

The default is to not change the precision model

public bool ChangePrecisionModel { get; set; }

Property Value

bool

Pointwise

Gets or sets whether the precision reduction will be done in pointwise fashion only. Pointwise precision reduction reduces the precision of the individual coordinates only, but does not attempt to recreate valid topology. This is only relevant for geometries containing polygonal components.

public bool Pointwise { get; set; }

Property Value

bool

RemoveCollapsedComponents

Gets or sets whether the reduction will result in collapsed components being removed completely, or simply being collapsed to an (invalid) Geometry of the same type. The default is to remove collapsed components.

public bool RemoveCollapsedComponents { get; set; }

Property Value

bool

Methods

Reduce(Geometry)

Reduces the precision of a geometry, according to the specified strategy of this reducer.

public Geometry Reduce(Geometry geom)

Parameters

geom Geometry

The geometry to reduce

Returns

Geometry

The precision-reduced geometry

Exceptions

ArgumentException

if the reduction fails due to input geometry is invalid.

Reduce(Geometry, PrecisionModel)

Reduces precision of a geometry, ensuring output geometry is valid. Collapsed linear and polygonal components are removed. The geometry precision model is not changed. Invalid input geometry may cause an error, unless the invalidity is below the scale of the precision reduction.

public static Geometry Reduce(Geometry g, PrecisionModel precModel)

Parameters

g Geometry

The geometry to reduce

precModel PrecisionModel

The precision model to use

Returns

Geometry

The reduced geometry

Exceptions

ArgumentException

Thrwon if the reduction fails due to invalid input geometry

ReduceKeepCollapsed(Geometry, PrecisionModel)

Reduces precision of a geometry, ensuring output polygonal geometry is valid, and preserving collapsed linear elements. The geometry precision model is not changed. Invalid input geometry may cause an error, unless the invalidity is below the scale of the precision reduction.

public static Geometry ReduceKeepCollapsed(Geometry geom, PrecisionModel pm)

Parameters

geom Geometry

pm PrecisionModel

Returns

Geometry

The reduced geometry

Exceptions

ArgumentException

Thrwon if the reduction fails due to invalid input geometry

ReducePointwise(Geometry, PrecisionModel)

Reduce precision of a geometry in a pointwise way. All input geometry elements are preserved in the output, including invalid polygons and collapsed polygons and linestrings. The output may not be valid, due to collapse or self-intersection. The geometry precision model is not changed. Invalid input geometry is allowed.

public static Geometry ReducePointwise(Geometry g, PrecisionModel precModel)

Parameters

g Geometry

The geometry to reduce

precModel PrecisionModel

The precision model to use

Returns

Geometry

The reduced geometry