com.vividsolutions.jts.linearref.LocationIndexOfPoint Maven / Gradle / Ivy
The newest version!
/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.vividsolutions.jts.linearref;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.util.Assert;
/**
* Computes the {@link LinearLocation} of the point
* on a linear {@link Geometry} nearest a given {@link Coordinate}.
* The nearest point is not necessarily unique; this class
* always computes the nearest point closest to
* the start of the geometry.
*/
class LocationIndexOfPoint
{
public static LinearLocation indexOf(Geometry linearGeom, Coordinate inputPt)
{
LocationIndexOfPoint locater = new LocationIndexOfPoint(linearGeom);
return locater.indexOf(inputPt);
}
public static LinearLocation indexOfAfter(Geometry linearGeom, Coordinate inputPt, LinearLocation minIndex)
{
LocationIndexOfPoint locater = new LocationIndexOfPoint(linearGeom);
return locater.indexOfAfter(inputPt, minIndex);
}
private Geometry linearGeom;
public LocationIndexOfPoint(Geometry linearGeom) {
this.linearGeom = linearGeom;
}
/**
* Find the nearest location along a linear {@link Geometry} to a given point.
*
* @param inputPt the coordinate to locate
* @return the location of the nearest point
*/
public LinearLocation indexOf(Coordinate inputPt)
{
return indexOfFromStart(inputPt, null);
}
/**
* Find the nearest {@link LinearLocation} along the linear {@link Geometry}
* to a given {@link Coordinate}
* after the specified minimum {@link LinearLocation}.
* If possible the location returned will be strictly greater than the
* minLocation.
* If this is not possible, the
* value returned will equal minLocation.
* (An example where this is not possible is when
* minLocation = [end of line] ).
*
* @param inputPt the coordinate to locate
* @param minIndex the minimum location for the point location
* @return the location of the nearest point
*/
public LinearLocation indexOfAfter(Coordinate inputPt, LinearLocation minIndex)
{
if (minIndex == null) return indexOf(inputPt);
// sanity check for minLocation at or past end of line
LinearLocation endLoc = LinearLocation.getEndLocation(linearGeom);
if (endLoc.compareTo(minIndex) <= 0)
return endLoc;
LinearLocation closestAfter = indexOfFromStart(inputPt, minIndex);
/**
* Return the minDistanceLocation found.
* This will not be null, since it was initialized to minLocation
*/
Assert.isTrue(closestAfter.compareTo(minIndex) >= 0,
"computed location is before specified minimum location");
return closestAfter;
}
private LinearLocation indexOfFromStart(Coordinate inputPt, LinearLocation minIndex)
{
double minDistance = Double.MAX_VALUE;
int minComponentIndex = 0;
int minSegmentIndex = 0;
double minFrac = -1.0;
LineSegment seg = new LineSegment();
for (LinearIterator it = new LinearIterator(linearGeom);
it.hasNext(); it.next()) {
if (! it.isEndOfLine()) {
seg.p0 = it.getSegmentStart();
seg.p1 = it.getSegmentEnd();
double segDistance = seg.distance(inputPt);
double segFrac = seg.segmentFraction(inputPt);
int candidateComponentIndex = it.getComponentIndex();
int candidateSegmentIndex = it.getVertexIndex();
if (segDistance < minDistance) {
// ensure after minLocation, if any
if (minIndex == null ||
minIndex.compareLocationValues(
candidateComponentIndex, candidateSegmentIndex, segFrac)
< 0
) {
// otherwise, save this as new minimum
minComponentIndex = candidateComponentIndex;
minSegmentIndex = candidateSegmentIndex;
minFrac = segFrac;
minDistance = segDistance;
}
}
}
}
if (minDistance == Double.MAX_VALUE) {
// no minimum was found past minLocation, so return it
return new LinearLocation(minIndex);
}
// otherwise, return computed location
LinearLocation loc = new LinearLocation(minComponentIndex, minSegmentIndex, minFrac);
return loc;
}
/**
* Computes the fraction of distance (in [0.0, 1.0])
* that a point occurs along a line segment.
* If the point is beyond either ends of the line segment,
* the closest fractional value (0.0 or 1.0) is returned.
*
* @param seg the line segment to use
* @param inputPt the point
* @return the fraction along the line segment the point occurs
*/
/*
// MD - no longer needed
private static double segmentFraction(
LineSegment seg,
Coordinate inputPt)
{
double segFrac = seg.projectionFactor(inputPt);
if (segFrac < 0.0)
segFrac = 0.0;
else if (segFrac > 1.0)
segFrac = 1.0;
return segFrac;
}
*/
}