geos::coverage::CoverageSimplifier Class Reference

#include <CoverageSimplifier.h>

Public Member Functions
	CoverageSimplifier (const std::vector< const Geometry * > &coverage)
std::vector< std::unique_ptr< Geometry > >	simplify (double tolerance)
std::vector< std::unique_ptr< Geometry > >	simplifyInner (double tolerance)

Static Public Member Functions
static std::vector< std::unique_ptr< Geometry > >	simplify (std::vector< const Geometry * > &coverage, double tolerance)
static std::vector< std::unique_ptr< Geometry > >	simplify (const std::vector< std::unique_ptr< Geometry >> &coverage, double tolerance)
static std::vector< std::unique_ptr< Geometry > >	simplifyInner (std::vector< const Geometry * > &coverage, double tolerance)
static std::vector< std::unique_ptr< Geometry > >	simplifyInner (const std::vector< std::unique_ptr< Geometry >> &coverage, double tolerance)

Detailed Description

Simplifies the boundaries of the polygons in a polygonal coverage while preserving the original coverage topology. An area-based simplification algorithm (similar to Visvalingam-Whyatt simplification) is used to provide high-quality results. Also supports simplifying just the inner edges in a coverage, which allows simplifying "patches" without affecting their boundary.

The amount of simplification is determined by a tolerance value, which is a non-negative quantity. It equates roughly to the maximum distance by which a simplified line can change from the original. (In fact, it is the square root of the area tolerance used in the Visvalingam-Whyatt algorithm.)

The simplified result coverage has the following characteristics:

• It has the same number and types of polygonal geometries as the input
• Node points (inner vertices shared by three or more polygons, or boundary vertices shared by two or more) are not changed
• If the input is a valid coverage, then so is the result

This class also supports inner simplification, which simplifies only edges of the coverage which are adjacent to two polygons. This allows partial simplification of a coverage, since a simplified subset of a coverage still matches the remainder of the coverage.

The input coverage should be valid according to CoverageValidator.

Author

Martin Davis

Constructor & Destructor Documentation

CoverageSimplifier()

geos::coverage::CoverageSimplifier::CoverageSimplifier

(

const std::vector< const Geometry * > &

coverage

)

Create a new coverage simplifier instance.

Parameters

coverage

a set of polygonal geometries forming a coverage

Member Function Documentation

simplify() [1/2]

std::vector<std::unique_ptr<Geometry> > geos::coverage::CoverageSimplifier::simplify

(

double

tolerance

)

Computes the simplified coverage, preserving the coverage topology.

Parameters

tolerance

the simplification tolerance

Returns

the simplified polygons

simplify() [2/2]

static std::vector<std::unique_ptr<Geometry> > geos::coverage::CoverageSimplifier::simplify ( std::vector< const Geometry * > &  coverage, double  tolerance  )

static

Simplifies the boundaries of a set of polygonal geometries forming a coverage, preserving the coverage topology.

Parameters

coverage	a set of polygonal geometries forming a coverage
tolerance	the simplification tolerance

Returns

the simplified polygons

simplifyInner() [1/2]

std::vector<std::unique_ptr<Geometry> > geos::coverage::CoverageSimplifier::simplifyInner

(

double

tolerance

)

Computes the inner-boundary simplified coverage, preserving the coverage topology, and leaving outer boundary edges unchanged.

Parameters

tolerance

the simplification tolerance

Returns

the simplified polygons

simplifyInner() [2/2]

static std::vector<std::unique_ptr<Geometry> > geos::coverage::CoverageSimplifier::simplifyInner ( std::vector< const Geometry * > &  coverage, double  tolerance  )

static

Simplifies the inner boundaries of a set of polygonal geometries forming a coverage, preserving the coverage topology. Edges which form the exterior boundary of the coverage are left unchanged.

Parameters

coverage	a set of polygonal geometries forming a coverage
tolerance	the simplification tolerance

Returns

the simplified polygons

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The documentation for this class was generated from the following file:

• CoverageSimplifier.h