LengthSubstring Class Reference

Computes a substring of a LineString between given distances along the line. More...

Collaboration diagram for LengthSubstring:

Public Member Functions
	LengthSubstring (LineString line)
LineString	getSubstring (double startDistance, double endDistance)

Static Public Member Functions
static LineString	getSubstring (LineString line, double startLength, double endLength)

Private Member Functions
LineString	computeSubstring (double startDistance, double endDistance)
	Assumes input is strictly valid (e.g. More...

Private Attributes
LineString	line

Detailed Description

Computes a substring of a LineString between given distances along the line.

• The distances are clipped to the actual line length
• If the start distance is equal to the end distance, a zero-length line with two identical points is returned
• FUTURE: If the start distance is greater than the end distance, an inverted section of the line is returned

FUTURE: should handle startLength > endLength, and flip the returned linestring. Also should handle negative lengths (they are measured from end of line backwards).

Constructor & Destructor Documentation

LengthSubstring()

LengthSubstring

(

LineString

line

)

References LengthSubstring.line.

Referenced by LengthSubstring.getSubstring().

                                          {
    this.line = line;
  }

Member Function Documentation

computeSubstring()

LineString computeSubstring ( double  startDistance, double  endDistance  )

private

Assumes input is strictly valid (e.g.

startDist < endDistance)

Parameters

startDistance
endDistance

Returns

Ensure there is enough coordinates to build a valid line. Make a 2-point line with duplicate coordinates, if necessary There will always be at least one coordinate in the coordList.

References LocatePoint.pointAlongSegment().

Referenced by LengthSubstring.getSubstring().

  {
    Coordinate[] coordinates = line.getCoordinates();
    CoordinateList newCoordinates = new CoordinateList();
    double segmentStartDistance = 0.0;
    double segmentEndDistance = 0.0;
    boolean started = false;
    int i = 0;
    LineSegment segment = new LineSegment();
    while (i < coordinates.length - 1 && endDistance > segmentEndDistance) {
      segment.p0 = coordinates[i];
      segment.p1 = coordinates[i + 1];
      i++;
      segmentStartDistance = segmentEndDistance;
      segmentEndDistance = segmentStartDistance + segment.getLength();

      if (startDistance > segmentEndDistance)
        continue;
      if (startDistance >= segmentStartDistance
          && startDistance < segmentEndDistance) {
        newCoordinates.add(LocatePoint.pointAlongSegment(segment.p0, segment.p1,
            startDistance - segmentStartDistance), false);
      }
      /*
      if (startDistance >= segmentStartDistance
          && startDistance == segmentEndDistance) {
        newCoordinates.add(new Coordinate(segment.p1), false);
      }
      */
      if (endDistance >= segmentEndDistance) {
        newCoordinates.add(new Coordinate(segment.p1), false);
      }
      if (endDistance >= segmentStartDistance
          && endDistance < segmentEndDistance) {
        newCoordinates.add(LocatePoint.pointAlongSegment(segment.p0, segment.p1,
            endDistance - segmentStartDistance), false);
      }
    }
    Coordinate[] newCoordinateArray = newCoordinates.toCoordinateArray();
    if (newCoordinateArray.length <= 1) {
      newCoordinateArray = new Coordinate[] { newCoordinateArray[0], newCoordinateArray[0]};
    }
    return line.getFactory().createLineString(newCoordinateArray);
  }

getSubstring() [1/2]

static LineString getSubstring ( LineString  line, double  startLength, double  endLength  )

static

References LengthSubstring.getSubstring(), and LengthSubstring.LengthSubstring().

Referenced by LengthSubstring.getSubstring().

                                                          {
    LengthSubstring ls = new LengthSubstring(line);
    return ls.getSubstring(startLength, endLength);
  }

getSubstring() [2/2]

LineString getSubstring	(	double	startDistance,
		double	endDistance
	)

References LengthSubstring.computeSubstring().

  {
    // future: if start > end, flip values and return an inverted line
    Assert.isTrue(startDistance <= endDistance, "inverted distances not currently supported");

    Coordinate[] coordinates = line.getCoordinates();
    // check for a zero-length segment and handle appropriately
    if (endDistance <= 0.0) {
      return line.getFactory().createLineString(
          new Coordinate[] { coordinates[0], coordinates[0]});
    }
    if (startDistance >= line.getLength()) { return line.getFactory()
                       .createLineString(
                       new Coordinate[] { coordinates[coordinates.length - 1],
    coordinates[coordinates.length - 1]}); }
    if (startDistance < 0.0) {
      startDistance = 0.0;
    }
    return computeSubstring(startDistance, endDistance);
  }

Member Data Documentation

line

LineString line

private

Referenced by LengthSubstring.LengthSubstring().