package com.vividsolutions.jts.linearref;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.util.Assert;
/**
* Computes the length index 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 LengthIndexOfPoint
{
public static double indexOf(Geometry linearGeom, Coordinate inputPt)
{
LengthIndexOfPoint locater = new LengthIndexOfPoint(linearGeom);
return locater.indexOf(inputPt);
}
public static double indexOfAfter(Geometry linearGeom, Coordinate inputPt, double minIndex)
{
LengthIndexOfPoint locater = new LengthIndexOfPoint(linearGeom);
return locater.indexOfAfter(inputPt, minIndex);
}
private Geometry linearGeom;
public LengthIndexOfPoint(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 double indexOf(Coordinate inputPt)
{
return indexOfFromStart(inputPt, -1.0);
}
/**
* Finds the nearest index along the linear {@link Geometry}
* to a given {@link Coordinate}
* after the specified minimum index.
* If possible the location returned will be strictly greater than the
* <code>minLocation</code>.
* If this is not possible, the
* value returned will equal <code>minLocation</code>.
* (An example where this is not possible is when
* minLocation = [end of line] ).
*
* @param inputPt the coordinate to locate
* @param minLocation the minimum location for the point location
* @return the location of the nearest point
*/
public double indexOfAfter(Coordinate inputPt, double minIndex)
{
if (minIndex < 0.0) return indexOf(inputPt);
// sanity check for minIndex at or past end of line
double endIndex = linearGeom.getLength();
if (endIndex < minIndex)
return endIndex;
double closestAfter = indexOfFromStart(inputPt, minIndex);
/**
* Return the minDistanceLocation found.
* This will not be null, since it was initialized to minLocation
*/
Assert.isTrue(closestAfter > minIndex,
"computed index is before specified minimum index");
return closestAfter;
}
private double indexOfFromStart(Coordinate inputPt, double minIndex)
{
double minDistance = Double.MAX_VALUE;
double ptMeasure = minIndex;
double segmentStartMeasure = 0.0;
LineSegment seg = new LineSegment();
LinearIterator it = new LinearIterator(linearGeom);
while (it.hasNext()) {
if (! it.isEndOfLine()) {
seg.p0 = it.getSegmentStart();
seg.p1 = it.getSegmentEnd();
double segDistance = seg.distance(inputPt);
double segMeasureToPt = segmentNearestMeasure(seg, inputPt, segmentStartMeasure);
if (segDistance < minDistance
&& segMeasureToPt > minIndex) {
ptMeasure = segMeasureToPt;
minDistance = segDistance;
}
segmentStartMeasure += seg.getLength();
}
it.next();
}
return ptMeasure;
}
private double segmentNearestMeasure(LineSegment seg, Coordinate inputPt,
double segmentStartMeasure)
{
// found new minimum, so compute location distance of point
double projFactor = seg.projectionFactor(inputPt);
if (projFactor <= 0.0)
return segmentStartMeasure;
if (projFactor <= 1.0)
return segmentStartMeasure + projFactor * seg.getLength();
// projFactor > 1.0
return segmentStartMeasure + seg.getLength();
}
}