geos

package
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 Go to latest Published: May 29, 2014 License: MIT Imports: 8 Imported by: 0

Documentation

Overview

Package geos provides support for creating and manipulating spatial data. At its core, it relies on the GEOS C library for the implementation of spatial operations and geometric algorithms.

Index

Examples

Constants

This section is empty.

Variables

View Source 
var (
	// ErrLineInterpolatePointDist is an error for an invalid interpolation
	// distance value.
	ErrLineInterpolatePointDist = errors.New("distance must between 0 and 1")
	// ErrLineInterpolatePointType is an error for an line interpolation point
	// performed on a non-linestring geometry.
	ErrLineInterpolatePointType = errors.New("geometry must be a linestring")
)

Functions

func Error 

func Error() error

Error gets the last error that occured in the GEOS C API as a Go error type.

func Version 

func Version() string

Version returns the version of the GEOS C API in use.

Types

type BufferOpts 

type BufferOpts struct {
	// QuadSegs is the number of quadrant segments.
	QuadSegs int
	// CapStyle is the end cap style.
	CapStyle CapStyle
	// JoinStyle is the line segment join style.
	JoinStyle JoinStyle
	// MitreLimit is the limit in the amount of a mitred join.
	MitreLimit float64
}

BufferOpts are options to the BufferWithOpts method.

type CapStyle 

type CapStyle int

CapStyle is the style of the cap at the end of a line segment. 

const (

	// CapRound is a round end cap.
	CapRound CapStyle
	// CapFlat is a flat end cap.
	CapFlat
	// CapSquare is a square end cap.
	CapSquare
)

type Coord 

type Coord struct {
	X, Y, Z float64
}

Coord represents a coordinate in 3-dimensional space.

func MustCoords 

func MustCoords(c []Coord, err error) []Coord

MustCoords is a helper that wraps a call to a function returning ([]Coord, error) and panics if the error is non-nil.

func NewCoord 

func NewCoord(x, y float64) Coord

NewCoord is the constructor for a Coord object.

func (Coord) String 

func (c Coord) String() string

String returns a (2d) string representation of a Coord.

type Geometry 

type Geometry struct {
	// contains filtered or unexported fields
}

Geometry represents a geometry object, which can be any one of the types of the Simple Features Specification of the Open GIS Consortium: 

Point
LineString
LinearRing
Polygon
MultiPoint
MultiLineString
MultiPolygon
GeometryCollection

func EmptyPolygon 

func EmptyPolygon() (*Geometry, error)

EmptyPolygon returns a new geometry of type Polygon that's empty (i.e., IsEmpty() == true).

func FromHex 

func FromHex(hex string) (*Geometry, error)

FromHex is a factory function that returns a new Geometry decoded from a Well-Known Binary (WKB) hex string.

func FromWKB 

func FromWKB(wkb []byte) (*Geometry, error)

FromWKB is a factory function that returns a new Geometry decoded from a Well-Known Binary (WKB).

func FromWKT 

func FromWKT(wkt string) (*Geometry, error)

FromWKT is a factory function that returns a new Geometry decoded from a Well-Known Text (WKT) string.

func Must 

func Must(g *Geometry, err error) *Geometry

Must is a helper that wraps a call to a function returning (*Geometry, error) and panics if the error is non-nil.

func NewCollection 

func NewCollection(_type GeometryType, geoms ...*Geometry) (*Geometry, error)

NewCollection returns a new geometry that is a collection containing multiple geometries given as variadic arguments. The type of the collection (in the SFS sense of type -- MultiPoint, MultiLineString, etc.) is determined by the first argument. If no geometries are given, the geometry is an empty version of the given collection type.

func NewLineString 

func NewLineString(coords ...Coord) (*Geometry, error)

NewLineString returns a new geometry of type LineString, initialized with the given coordinates. If no coordinates are given, it's an empty geometry (IsEmpty() == true).

func NewLinearRing 

func NewLinearRing(coords ...Coord) (*Geometry, error)

NewLinearRing returns a new geometry of type LinearRing, initialized with the given coordinates. The number of coordinates must either be zero (none given), in which case it's an empty geometry (IsEmpty() == true), or >= 4.

func NewPoint 

func NewPoint(coords ...Coord) (*Geometry, error)

NewPoint returns a new geometry of type Point, initialized with the given coordinate(s). If no coordinates are given, it's an empty geometry (i.e., IsEmpty() == true). It's an error if more than one coordinate is given.

func NewPolygon 

func NewPolygon(shell []Coord, holes ...[]Coord) (*Geometry, error)

NewPolygon returns a new geometry of type Polygon, initialized with the given shell (exterior ring) and slice of holes (interior rings). The shell and holes slice are themselves slices of coordinates. A shell is required, and a variadic number of holes (therefore are optional).

To create a new polygon from existing linear ring Geometry objects, use PolygonFromGeom.

func PolygonFromGeom 

func PolygonFromGeom(shell *Geometry, holes ...*Geometry) (*Geometry, error)

PolygonFromGeom returns a new geometry of type Polygon, initialized with the given shell (exterior ring) and slice of holes (interior rings). The shell and slice of holes are geometry objects, and expected to be LinearRings.

func (*Geometry) Area 

func (g *Geometry) Area() (float64, error)

Area returns the area of the geometry, which must be a areal geometry like a polygon or multipolygon.

func (*Geometry) Boundary 

func (g *Geometry) Boundary() (*Geometry, error)

Boundary is the boundary of the geometry.

func (*Geometry) Buffer 

func (g *Geometry) Buffer(d float64) (*Geometry, error)

Buffer computes a new geometry as the dilation (position amount) or erosion (negative amount) of the geometry -- a sum or difference, respectively, of the geometry with a circle of radius of the absolute value of the buffer amount.

func (*Geometry) BufferWithOpts 

func (g *Geometry) BufferWithOpts(width float64, opts BufferOpts) (*Geometry, error)

BufferWithOpts computes a new geometry as the dilation (position amount) or erosion (negative amount) of the geometry -- a sum or difference, respectively, of the geometry with a circle of radius of the absolute value of the buffer amount.

BufferWithOpts gives the user more control than Buffer over the parameters of the buffering, including:

  • # of quadrant segments (defaults to 8 in Buffer)
  • mitre limit (defaults to 5.0 in Buffer)
  • end cap style (see CapStyle consts)
  • join style (see JoinStyle consts)

func (*Geometry) Centroid 

func (g *Geometry) Centroid() (*Geometry, error)

Centroid is the center point of the geometry.

func (*Geometry) Clone 

func (g *Geometry) Clone() (*Geometry, error)

Clone performs a deep copy on the geometry.

func (*Geometry) Contains 

func (g *Geometry) Contains(other *Geometry) (bool, error)

Contains returns true if every point of the other is a point of this geometry, and the interiors of the two geometries have at least one point in common.

func (*Geometry) ConvexHull 

func (g *Geometry) ConvexHull() (*Geometry, error)

ConvexHull computes the smallest convex geometry that contains all the points of the geometry.

func (*Geometry) CoordDimension 

func (g *Geometry) CoordDimension() int

CoordDimension returns the number of dimensions of the coordinates of the geometry (2 or 3).

func (*Geometry) Coords 

func (g *Geometry) Coords() ([]Coord, error)

Coords returns a slice of Coord, a sequence of coordinates underlying the point, linestring, or linear ring.

func (*Geometry) CoveredBy 

func (g *Geometry) CoveredBy(other *Geometry) (bool, error)

CoveredBy returns true if every point of this geometry is a point of the other geometry.

func (*Geometry) Covers 

func (g *Geometry) Covers(other *Geometry) (bool, error)

Covers returns true if every point of the other geometry is a point of this geometry.

func (*Geometry) Crosses 

func (g *Geometry) Crosses(other *Geometry) (bool, error)

Crosses returns true if the two geometries have some but not all interior points in common.

func (*Geometry) Difference 

func (g *Geometry) Difference(other *Geometry) (*Geometry, error)

Difference returns a new geometry representing the points making up this geometry that do not make up the other.

func (*Geometry) Dimension 

func (g *Geometry) Dimension() int

Dimension returns the number of dimensions geometry, eg., 1 for point, 2 for linestring.

func (*Geometry) Disjoint 

func (g *Geometry) Disjoint(other *Geometry) (bool, error)

Disjoint returns true if the two geometries have no point in common.

func (*Geometry) Distance 

func (g *Geometry) Distance(other *Geometry) (float64, error)

Distance returns the Cartesian distance between the two geometries.

func (*Geometry) EndPoint 

func (g *Geometry) EndPoint() (*Geometry, error)

EndPoint returns the (n-1)th point of the geometry. Geometry must be LineString.

func (*Geometry) Envelope 

func (g *Geometry) Envelope() (*Geometry, error)

Envelope is the bounding box of a geometry, as a polygon.

func (*Geometry) Equals 

func (g *Geometry) Equals(other *Geometry) (bool, error)

Equals returns true if the two geometries have at least one point in common, and no point of either geometry lies in the exterior of the other geometry.

func (*Geometry) EqualsExact 

func (g *Geometry) EqualsExact(other *Geometry, tolerance float64) (bool, error)

EqualsExact returns true if both geometries are Equal, as evaluated by their points being within the given tolerance.

func (*Geometry) Geometry 

func (g *Geometry) Geometry(n int) (*Geometry, error)

Geometry returns the nth sub-geometry of the geometry (eg., of a collection).

func (*Geometry) HasZ 

func (g *Geometry) HasZ() (bool, error)

HasZ returns true if the geometry is 3D.

func (*Geometry) HausdorffDistance 

func (g *Geometry) HausdorffDistance(other *Geometry) (float64, error)

HausdorffDistance computes the maximum distance of the geometry to the nearest point in the other geometry (i.e., considers the whole shape and position of the geometries).

func (*Geometry) HausdorffDistanceDensify 

func (g *Geometry) HausdorffDistanceDensify(other *Geometry, densifyFrac float64) (float64, error)

HausdorffDistanceDensify computes the Hausdorff distance (see HausdorffDistance) with an additional densification fraction amount.

func (*Geometry) Hex 

func (g *Geometry) Hex() ([]byte, error)

Hex returns the geometry as a Well-Known Binary (WKB) hex-encoded byte slice.

func (*Geometry) Holes 

func (g *Geometry) Holes() ([]*Geometry, error)

Holes returns a slice of geometries (LinearRings) representing the interior rings of a polygon (possibly nil). Geometry must be a Polygon.

func (*Geometry) Interpolate 

func (g *Geometry) Interpolate(dist float64) (*Geometry, error)

Interpolate returns the closest point to given distance within geometry. This geometry must be a LineString.

func (*Geometry) Intersection 

func (g *Geometry) Intersection(other *Geometry) (*Geometry, error)

Intersection returns a new geometry representing the points shared by this geometry and the other.

func (*Geometry) Intersects 

func (g *Geometry) Intersects(other *Geometry) (bool, error)

Intersects returns true if the two geometries have at least one point in common.

func (*Geometry) IsClosed 

func (g *Geometry) IsClosed() (bool, error)

IsClosed returns true if the geometry is closed (i.e., start & end points equal).

func (*Geometry) IsEmpty 

func (g *Geometry) IsEmpty() (bool, error)

IsEmpty returns true if the set of points of this geometry is empty (i.e., the empty geometry).

func (*Geometry) IsRing 

func (g *Geometry) IsRing() (bool, error)

IsRing returns true if the lineal geometry has the ring property.

func (*Geometry) IsSimple 

func (g *Geometry) IsSimple() (bool, error)

IsSimple returns true iff the only self-intersections are at boundary points.

func (*Geometry) Length 

func (g *Geometry) Length() (float64, error)

Length returns the length of the geometry, which must be a lineal geometry like a linestring or linear ring.

func (*Geometry) LineInterpolatePoint 

func (g *Geometry) LineInterpolatePoint(dist float64) (*Geometry, error)

LineInterpolatePoint interpolates a point along a line.

Example 
package main

import (
	"fmt"

	"github.com/paulsmith/gogeos/geos"
)

func main() {
	line := geos.Must(geos.FromWKT("LINESTRING(25 50, 100 125, 150 190)"))
	pt := geos.Must(line.LineInterpolatePoint(0.20))
	fmt.Println(pt)
}

Output:

POINT (51.5974135047432014 76.5974135047432014)

func (*Geometry) LineMerge 

func (g *Geometry) LineMerge() (*Geometry, error)

LineMerge will merge together a collection of LineStrings where they touch only at their start and end points. The LineStrings must be fully noded. The resulting geometry is a new collection.

func (*Geometry) NCoordinate 

func (g *Geometry) NCoordinate() (int, error)

NCoordinate returns the number of coordinates of the geometry.

func (*Geometry) NGeometry 

func (g *Geometry) NGeometry() (int, error)

NGeometry returns the number of component geometries (eg., for a collection).

func (*Geometry) NPoint 

func (g *Geometry) NPoint() (int, error)

NPoint returns the number of points in the geometry.

func (*Geometry) Normalize 

func (g *Geometry) Normalize() error

Normalize computes the normal form of the geometry. Modifies geometry in-place, clone first if this is not wanted/safe.

func (*Geometry) OffsetCurve 

func (g *Geometry) OffsetCurve(distance float64, opts BufferOpts) (*Geometry, error)

OffsetCurve computes a new linestring that is offset from the input linestring by the given distance and buffer options. A negative distance is offset on the right side; positive distance offset on the left side.

func (*Geometry) Overlaps 

func (g *Geometry) Overlaps(other *Geometry) (bool, error)

Overlaps returns true if the geometries have some but not all points in common, they have the same dimension, and the intersection of the interiors of the two geometries has the same dimension as the geometries themselves.

func (*Geometry) Point 

func (g *Geometry) Point(n int) (*Geometry, error)

Point returns the nth point of the geometry. Geometry must be LineString.

func (*Geometry) PointOnSurface 

func (g *Geometry) PointOnSurface() (*Geometry, error)

PointOnSurface computes a point geometry guaranteed to be on the surface of the geometry.

func (*Geometry) Prepare 

func (g *Geometry) Prepare() *PGeometry

Prepare returns a new prepared geometry from the geometry -- see PGeometry

func (*Geometry) Project 

func (g *Geometry) Project(p *Geometry) float64

Project returns distance of point projected on this geometry from origin. This must be a lineal geometry.

func (*Geometry) ProjectNormalized 

func (g *Geometry) ProjectNormalized(p *Geometry) float64

ProjectNormalized returns distance of point projected on this geometry from origin, divided by its length. This must be a lineal geometry.

func (*Geometry) Relate 

func (g *Geometry) Relate(other *Geometry) (string, error)

Relate computes the intersection matrix (Dimensionally Extended Nine-Intersection Model (DE-9IM) matrix) for the spatial relationship between the two geometries.

func (*Geometry) RelatePat 

func (g *Geometry) RelatePat(other *Geometry, pat string) (bool, error)

RelatePat returns true if the DE-9IM matrix equals the intersection matrix of the two geometries.

func (*Geometry) SRID 

func (g *Geometry) SRID() (int, error)

SRID returns the geometry's SRID, if set.

func (*Geometry) SetSRID 

func (g *Geometry) SetSRID(srid int)

SetSRID sets the geometry's SRID.

func (*Geometry) SharedPaths 

func (g *Geometry) SharedPaths(other *Geometry) (*Geometry, error)

SharedPaths finds paths shared between the two given lineal geometries. Returns a GeometryCollection having two elements:

  • first element is a MultiLineString containing shared paths having the _same_ direction on both inputs
  • second element is a MultiLineString containing shared paths having the _opposite_ direction on the two inputs

func (*Geometry) Shell 

func (g *Geometry) Shell() (*Geometry, error)

Shell returns the exterior ring (a LinearRing) of the geometry. Geometry must be a Polygon.

func (*Geometry) Simplify 

func (g *Geometry) Simplify(tolerance float64) (*Geometry, error)

Simplify returns a geometry simplified by amount given by tolerance. May not preserve topology -- see SimplifyP.

func (*Geometry) SimplifyP 

func (g *Geometry) SimplifyP(tolerance float64) (*Geometry, error)

SimplifyP returns a geometry simplified by amount given by tolerance. Unlike Simplify, SimplifyP guarantees it will preserve topology.

func (*Geometry) Snap 

func (g *Geometry) Snap(other *Geometry, tolerance float64) (*Geometry, error)

Snap returns a new geometry where the geometry is snapped to the given geometry by given tolerance.

func (*Geometry) StartPoint 

func (g *Geometry) StartPoint() (*Geometry, error)

StartPoint returns the 0th point of the geometry. Geometry must be LineString.

func (*Geometry) String 

func (g *Geometry) String() string

String returns a string encoding of the geometry, in Well-Known Text (WKT) format, or the empty string if there is an error creating the encoding.

func (*Geometry) SymDifference 

func (g *Geometry) SymDifference(other *Geometry) (*Geometry, error)

SymDifference returns a new geometry representing the set combining the points in this geometry not in the other, and the points in the other geometry and not in this.

func (*Geometry) ToWKT 

func (g *Geometry) ToWKT() (string, error)

ToWKT returns a string encoding of the geometry, in Well-Known Text (WKT) format.

func (*Geometry) Touches 

func (g *Geometry) Touches(other *Geometry) (bool, error)

Touches returns true if the two geometries have at least one point in common, but their interiors do not intersect.

func (*Geometry) Type 

func (g *Geometry) Type() (GeometryType, error)

Type returns the SFS type of the geometry.

func (*Geometry) UnaryUnion 

func (g *Geometry) UnaryUnion() (*Geometry, error)

UnaryUnion computes the union of all the constituent geometries of the geometry.

func (*Geometry) Union 

func (g *Geometry) Union(other *Geometry) (*Geometry, error)

Union returns a new geometry representing all points in this geometry and the other.

func (*Geometry) UniquePoints 

func (g *Geometry) UniquePoints() (*Geometry, error)

UniquePoints return all distinct vertices of input geometry as a MultiPoint.

func (*Geometry) WKB 

func (g *Geometry) WKB() ([]byte, error)

WKB returns the geoemtry encoded as a Well-Known Binary (WKB).

func (*Geometry) Within 

func (g *Geometry) Within(other *Geometry) (bool, error)

Within returns true if every point of this geometry is a point of the other, and the interiors of the two geometries have at least one point in common.

func (*Geometry) X 

func (g *Geometry) X() (float64, error)

X returns the x ordinate of the geometry. Geometry must be a Point.

func (*Geometry) Y 

func (g *Geometry) Y() (float64, error)

Y returns the y ordinate of the geometry. Geometry must be a Point

type GeometryType 

type GeometryType C.int

GeometryType represents the various geometry types supported by GEOS, and correspond to OGC Simple Features geometry types. 

const (
	// POINT is a 0-dimensional geometric object, a single location is geometric
	// space.
	POINT GeometryType = C.GEOS_POINT
	// LINESTRING is a curve with linear interpolation between points.
	LINESTRING GeometryType = C.GEOS_LINESTRING
	// LINEARRING is a linestring that is both closed and simple.
	LINEARRING GeometryType = C.GEOS_LINEARRING
	// POLYGON is a planar surface with 1 exterior boundary and 0 or more
	// interior boundaries.
	POLYGON GeometryType = C.GEOS_POLYGON
	// MULTIPOINT is a 0-dimensional geometry collection, the elements of which
	// are restricted to points.
	MULTIPOINT GeometryType = C.GEOS_MULTIPOINT
	// MULTILINESTRING is a 1-dimensional geometry collection, the elements of
	// which are restricted to linestrings.
	MULTILINESTRING GeometryType = C.GEOS_MULTILINESTRING
	// MULTIPOLYGON is a 2-dimensional geometry collection, the elements of
	// which are restricted to polygons.
	MULTIPOLYGON GeometryType = C.GEOS_MULTIPOLYGON
	// GEOMETRYCOLLECTION is a geometric object that is a collection of some
	// number of geometric objects.
	GEOMETRYCOLLECTION GeometryType = C.GEOS_GEOMETRYCOLLECTION
)

func (GeometryType) String 

func (t GeometryType) String() string

type JoinStyle 

type JoinStyle int

JoinStyle is the style of the joint of two line segments. 

const (

	// JoinRound is a round segment join style.
	JoinRound JoinStyle
	// JoinMitre is a mitred segment join style.
	JoinMitre
	// JoinBevel is a beveled segment join style.
	JoinBevel
)

type PGeometry 

type PGeometry struct {
	// contains filtered or unexported fields
}

PGeometry represents a "prepared geometry", a type of geometry object that is optimized for a limited set of operations.

func PrepareGeometry 

func PrepareGeometry(g *Geometry) *PGeometry

PrepareGeometry constructs a prepared geometry from a normal geometry object.

func (*PGeometry) Contains 

func (p *PGeometry) Contains(other *Geometry) (bool, error)

Contains computes whether the prepared geometry contains the other prepared geometry.

func (*PGeometry) ContainsP 

func (p *PGeometry) ContainsP(other *Geometry) (bool, error)

ContainsP computes whether the prepared geometry properly contains the other prepared geometry.

func (*PGeometry) CoveredBy 

func (p *PGeometry) CoveredBy(other *Geometry) (bool, error)

CoveredBy computes whether the prepared geometry is covered by the other prepared geometry.

func (*PGeometry) Covers 

func (p *PGeometry) Covers(other *Geometry) (bool, error)

Covers computes whether the prepared geometry covers the other prepared geometry.

func (*PGeometry) Crosses 

func (p *PGeometry) Crosses(other *Geometry) (bool, error)

Crosses computes whether the prepared geometry crosses the other prepared geometry.

func (*PGeometry) Disjoint 

func (p *PGeometry) Disjoint(other *Geometry) (bool, error)

Disjoint computes whether the prepared geometry is disjoint from the other prepared geometry.

func (*PGeometry) Intersects 

func (p *PGeometry) Intersects(other *Geometry) (bool, error)

Intersects computes whether the prepared geometry intersects the other prepared geometry.

func (*PGeometry) Overlaps 

func (p *PGeometry) Overlaps(other *Geometry) (bool, error)

Overlaps computes whether the prepared geometry overlaps the other prepared geometry.

func (*PGeometry) Touches 

func (p *PGeometry) Touches(other *Geometry) (bool, error)

Touches computes whether the prepared geometry touches the other prepared geometry.

func (*PGeometry) Within 

func (p *PGeometry) Within(other *Geometry) (bool, error)

Within computes whether the prepared geometry is within the other prepared geometry.

Source Files

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