org.locationtech.jts.algorithm.BoundaryNodeRule Maven / Gradle / Ivy
/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.algorithm;
import org.locationtech.jts.geom.LineString;
import org.locationtech.jts.geom.Lineal;
import org.locationtech.jts.geom.LinearRing;
import org.locationtech.jts.geom.MultiLineString;
import org.locationtech.jts.operation.BoundaryOp;
import org.locationtech.jts.operation.IsSimpleOp;
import org.locationtech.jts.operation.relate.RelateOp;
/**
* An interface for rules which determine whether node points
* which are in boundaries of {@link Lineal} geometry components
* are in the boundary of the parent geometry collection.
* The SFS specifies a single kind of boundary node rule,
* the {@link Mod2BoundaryNodeRule} rule.
* However, other kinds of Boundary Node Rules are appropriate
* in specific situations (for instance, linear network topology
* usually follows the {@link EndPointBoundaryNodeRule}.)
* Some JTS operations
* (such as {@link RelateOp}, {@link BoundaryOp} and {@link IsSimpleOp})
* allow the BoundaryNodeRule to be specified,
* and respect the supplied rule when computing the results of the operation.
*
* An example use case for a non-SFS-standard Boundary Node Rule is
* that of checking that a set of {@link LineString}s have
* valid linear network topology, when turn-arounds are represented
* as closed rings. In this situation, the entry road to the
* turn-around is only valid when it touches the turn-around ring
* at the single (common) endpoint. This is equivalent
* to requiring the set of LineStrings to be
* simple under the {@link EndPointBoundaryNodeRule}.
* The SFS-standard {@link Mod2BoundaryNodeRule} is not
* sufficient to perform this test, since it
* states that closed rings have no boundary points.
*
* This interface and its subclasses follow the Strategy design pattern.
*
* @author Martin Davis
* @version 1.7
*
* @see RelateOp
* @see BoundaryOp
* @see IsSimpleOp
* @see PointLocator
*/
public interface BoundaryNodeRule
{
/**
* Tests whether a point that lies in boundaryCount
* geometry component boundaries is considered to form part of the boundary
* of the parent geometry.
*
* @param boundaryCount the number of component boundaries that this point occurs in
* @return true if points in this number of boundaries lie in the parent boundary
*/
boolean isInBoundary(int boundaryCount);
/**
* The Mod-2 Boundary Node Rule (which is the rule specified in the OGC SFS).
* @see Mod2BoundaryNodeRule
*/
public static final BoundaryNodeRule MOD2_BOUNDARY_RULE = new Mod2BoundaryNodeRule();
/**
* The Endpoint Boundary Node Rule.
* @see EndPointBoundaryNodeRule
*/
public static final BoundaryNodeRule ENDPOINT_BOUNDARY_RULE = new EndPointBoundaryNodeRule();
/**
* The MultiValent Endpoint Boundary Node Rule.
* @see MultiValentEndPointBoundaryNodeRule
*/
public static final BoundaryNodeRule MULTIVALENT_ENDPOINT_BOUNDARY_RULE = new MultiValentEndPointBoundaryNodeRule();
/**
* The Monovalent Endpoint Boundary Node Rule.
* @see MonoValentEndPointBoundaryNodeRule
*/
public static final BoundaryNodeRule MONOVALENT_ENDPOINT_BOUNDARY_RULE = new MonoValentEndPointBoundaryNodeRule();
/**
* The Boundary Node Rule specified by the OGC Simple Features Specification,
* which is the same as the Mod-2 rule.
* @see Mod2BoundaryNodeRule
*/
public static final BoundaryNodeRule OGC_SFS_BOUNDARY_RULE = MOD2_BOUNDARY_RULE;
/**
* A {@link BoundaryNodeRule} specifies that points are in the
* boundary of a lineal geometry iff
* the point lies on the boundary of an odd number
* of components.
* Under this rule {@link LinearRing}s and closed
* {@link LineString}s have an empty boundary.
*
* This is the rule specified by the OGC SFS,
* and is the default rule used in JTS.
*
* @author Martin Davis
* @version 1.7
*/
public static class Mod2BoundaryNodeRule
implements BoundaryNodeRule
{
public boolean isInBoundary(int boundaryCount)
{
// the "Mod-2 Rule"
return boundaryCount % 2 == 1;
}
}
/**
* A {@link BoundaryNodeRule} which specifies that any points which are endpoints
* of lineal components are in the boundary of the
* parent geometry.
* This corresponds to the "intuitive" topological definition
* of boundary.
* Under this rule {@link LinearRing}s have a non-empty boundary
* (the common endpoint of the underlying LineString).
*
* This rule is useful when dealing with linear networks.
* For example, it can be used to check
* whether linear networks are correctly noded.
* The usual network topology constraint is that linear segments may touch only at endpoints.
* In the case of a segment touching a closed segment (ring) at one point,
* the Mod2 rule cannot distinguish between the permitted case of touching at the
* node point and the invalid case of touching at some other interior (non-node) point.
* The EndPoint rule does distinguish between these cases,
* so is more appropriate for use.
*
* @author Martin Davis
* @version 1.7
*/
public static class EndPointBoundaryNodeRule
implements BoundaryNodeRule
{
public boolean isInBoundary(int boundaryCount)
{
return boundaryCount > 0;
}
}
/**
* A {@link BoundaryNodeRule} which determines that only
* endpoints with valency greater than 1 are on the boundary.
* This corresponds to the boundary of a {@link MultiLineString}
* being all the "attached" endpoints, but not
* the "unattached" ones.
*
* @author Martin Davis
* @version 1.7
*/
public static class MultiValentEndPointBoundaryNodeRule
implements BoundaryNodeRule
{
public boolean isInBoundary(int boundaryCount)
{
return boundaryCount > 1;
}
}
/**
* A {@link BoundaryNodeRule} which determines that only
* endpoints with valency of exactly 1 are on the boundary.
* This corresponds to the boundary of a {@link MultiLineString}
* being all the "unattached" endpoints.
*
* @author Martin Davis
* @version 1.7
*/
public static class MonoValentEndPointBoundaryNodeRule
implements BoundaryNodeRule
{
public boolean isInBoundary(int boundaryCount)
{
return boundaryCount == 1;
}
}
}