Class OffsetCurve

Computes an offset curve from a geometry. An offset curve is a linear geometry which is offset a given distance from the input. If the offset distance is positive the curve lies on the left side of the input; if it is negative the curve is on the right side. The curve(s) have the same direction as the input line(s). The result for a zero offset distance is a copy of the input linework.

The offset curve is based on the boundary of the buffer for the geometry at the offset distance(see BufferOp. The normal mode of operation is to return the sections of the buffer boundarywhich lie on the raw offset curve (obtained via RawOffset(LineString, double). The offset curve will contain multiple sections if the input self-intersects or has close approaches.The computed sections are ordered along the raw offset curve. Sections are disjoint.They never self-intersect, but may be rings.

• For a LineString the offset curve is a linear geometry (LineString or MultiLineString).
• For a Point or MultiPoint the offset curve is an empty LineString.
• For a Polygon the offset curve is the boundary of the polygon buffer (which may be a MultiLineString).
• For a collection the output is a MultiLineString containing the offset curves of the elements.

In "joined" mode (see {@link #setJoined(boolean)} the sections computed for each input line are joined into a single offset curve line. The joined curve may self-intersect. At larger offset distances the curve may contain "flat-line" artifacts in places where the input self-intersects.

Offset curves support setting the number of quadrant segments, the join style, and the mitre limit(if applicable) via the BufferParameters.

Inheritance

object

OffsetCurve

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: NetTopologySuite.Operation.Buffer

Assembly: NetTopologySuite.dll

Syntax

public class OffsetCurve

Constructors

OffsetCurve(Geometry, double)

Creates a new instance for computing an offset curve for a geometry at a given distance. with default quadrant segments(DefaultQuadrantSegments and join style (DefaultJoinStyle).

Declaration

public OffsetCurve(Geometry geom, double distance)

Parameters

Type	Name	Description
Geometry	geom	The geometry
double	distance	The offset distance (positive for left, negative for right)

OffsetCurve(Geometry, double, BufferParameters)

Creates a new instance for computing an offset curve for a geometry at a given distance. setting the quadrant segments, join style and mitre limit via BufferParameters.

Declaration

public OffsetCurve(Geometry geom, double distance, BufferParameters bufParams)

Parameters

Type	Name	Description
Geometry	geom	The geometry
double	distance	The offset distance (positive for left, negative for right)
BufferParameters	bufParams	The buffer paramters to use

Properties

Joined

Gets or sets a value indicating if a single curve line for each input linear component is computed by joining curve sections in order along the raw offset curve. The default mode is to compute separate curve sections.

Declaration

public bool Joined { get; set; }

Property Value

Type	Description
bool

Methods

GetCurve()

Gets the computed offset curve.

Declaration

public Geometry GetCurve()

Returns

Type	Description
Geometry	The offset curve geometry

GetCurve(Geometry, double)

Computes the offset curve of a geometry at a given distance.

Declaration

public static Geometry GetCurve(Geometry geom, double distance)

Parameters

Type	Name	Description
Geometry	geom	A geometry
double	distance	the offset distance (positive for left, negative for right)

Returns

Type	Description
Geometry	The offset curve

GetCurve(Geometry, double, int, JoinStyle, double)

Computes the offset curve of a geometry at a given distance, with specified quadrant segments, join style and mitre limit.

Declaration

public static Geometry GetCurve(Geometry geom, double distance, int quadSegs = -1, JoinStyle joinStyle = JoinStyle.Round, double mitreLimit = -1)

Parameters

Type	Name	Description
Geometry	geom	A geometry
double	distance	The offset distance (positive for left, negative for right)
int	quadSegs	The quadrant segments
JoinStyle	joinStyle	The join style
double	mitreLimit	The mitre limit

Returns

Type	Description
Geometry	The offset curve

GetCurveJoined(Geometry, double)

Computes the offset curve of a geometry at a given distance, joining curve sections into a single line for each input line.

Declaration

public static Geometry GetCurveJoined(Geometry geom, double distance)

Parameters

Type	Name	Description
Geometry	geom	A geometry
double	distance	the offset distance (positive for left, negative for right)

Returns

Type	Description
Geometry	The joined offset curve

RawOffset(LineString, double)

Gets the raw offset curve for a line at a given distance, with default buffer parameters.

Declaration

public static Coordinate[] RawOffset(LineString line, double distance)

Parameters

Type	Name	Description
LineString	line	The LineString to offset
double	distance	The offset distance (positive for left, negative for right)

Returns

Type	Description
Coordinate[]	The raw offset line

RawOffset(LineString, double, BufferParameters)

Gets the raw offset curve for a line at a given distance. The quadrant segments, join style and mitre limit can be specified via BufferParameters.

The raw offset line may contain loops and other artifacts which are not present in the true offset curve.

Declaration

public static Coordinate[] RawOffset(LineString line, double distance, BufferParameters bufParams)

Parameters

Type	Name	Description
LineString	line	The LineString to offset
double	distance	The offset distance (positive for left, negative for right)
BufferParameters	bufParams	The buffer parameters to use

Returns

Type	Description
Coordinate[]	The raw offset curve points