com.vividsolutions.jts.operation.buffer.BufferOp Maven / Gradle / Ivy
/*
* 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.operation.buffer;
/**
* @version 1.7
*/
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.precision.SimpleGeometryPrecisionReducer;
import com.vividsolutions.jts.math.MathUtil;
import com.vividsolutions.jts.noding.*;
import com.vividsolutions.jts.noding.snapround.*;
//import debug.*;
/**
* Computes the buffer of a geometry, for both positive and negative buffer distances.
*
* In GIS, the positive (or negative) buffer of a geometry is defined as
* the Minkowski sum (or difference) of the geometry
* with a circle of radius equal to the absolute value of the buffer distance.
* In the CAD/CAM world buffers are known as offset curves.
* In morphological analysis the
* operation of positive and negative buffering
* is referred to as erosion and dilation
*
* The buffer operation always returns a polygonal result.
* The negative or zero-distance buffer of lines and points is always an empty {@link Polygon}.
*
* Since true buffer curves may contain circular arcs,
* computed buffer polygons are only approximations to the true geometry.
* The user can control the accuracy of the approximation by specifying
* the number of linear segments used to approximate arcs.
* This is specified via {@link BufferParameters#setQuadrantSegments(int)} or {@link #setQuadrantSegments(int)}.
*
* The end cap style of a linear buffer may be {@link BufferParameters#setEndCapStyle(int) specified}. The
* following end cap styles are supported:
*
{@link BufferParameters#CAP_ROUND} - the usual round end caps
* - {@link BufferParameters#CAP_BUTT} - end caps are truncated flat at the line ends
*
- {@link BufferParameters#CAP_SQUARE} - end caps are squared off at the buffer distance beyond the line ends
*
*
* The join style of the corners in a buffer may be {@link BufferParameters#setJoinStyle(int) specified}. The
* following join styles are supported:
*
{@link BufferParameters#JOIN_ROUND} - the usual round join
* - {@link BufferParameters#JOIN_MITRE} - corners are "sharp" (up to a {@link BufferParameters#getMitreLimit() distance limit})
*
- {@link BufferParameters#JOIN_BEVEL} - corners are beveled (clipped off).
*
*
* The buffer algorithm can perform simplification on the input to increase performance.
* The simplification is performed a way that always increases the buffer area
* (so that the simplified input covers the original input).
* The degree of simplification can be {@link BufferParameters#setSimplifyFactor(double) specified},
* with a {@link BufferParameters#DEFAULT_SIMPLIFY_FACTOR default} used otherwise.
* Note that if the buffer distance is zero then so is the computed simplify tolerance,
* no matter what the simplify factor.
*
* @version 1.7
*/
public class BufferOp
{
/**
* Specifies a round line buffer end cap style.
* @deprecated use BufferParameters
*/
public static final int CAP_ROUND = BufferParameters.CAP_ROUND;
/**
* Specifies a butt (or flat) line buffer end cap style.
* @deprecated use BufferParameters
*/
public static final int CAP_BUTT = BufferParameters.CAP_FLAT;
/**
* Specifies a butt (or flat) line buffer end cap style.
* @deprecated use BufferParameters
*/
public static final int CAP_FLAT = BufferParameters.CAP_FLAT;
/**
* Specifies a square line buffer end cap style.
* @deprecated use BufferParameters
*/
public static final int CAP_SQUARE = BufferParameters.CAP_SQUARE;
/**
* A number of digits of precision which leaves some computational "headroom"
* for floating point operations.
*
* This value should be less than the decimal precision of double-precision values (16).
*/
private static int MAX_PRECISION_DIGITS = 12;
/**
* Compute a scale factor to limit the precision of
* a given combination of Geometry and buffer distance.
* The scale factor is determined by
* the number of digits of precision in the (geometry + buffer distance),
* limited by the supplied maxPrecisionDigits value.
*
* The scale factor is based on the absolute magnitude of the (geometry + buffer distance).
* since this determines the number of digits of precision which must be handled.
*
* @param g the Geometry being buffered
* @param distance the buffer distance
* @param maxPrecisionDigits the max # of digits that should be allowed by
* the precision determined by the computed scale factor
*
* @return a scale factor for the buffer computation
*/
private static double precisionScaleFactor(Geometry g,
double distance,
int maxPrecisionDigits)
{
Envelope env = g.getEnvelopeInternal();
double envMax = MathUtil.max(
Math.abs(env.getMaxX()),
Math.abs(env.getMaxY()),
Math.abs(env.getMinX()),
Math.abs(env.getMinY())
);
double expandByDistance = distance > 0.0 ? distance : 0.0;
double bufEnvMax = envMax + 2 * expandByDistance;
// the smallest power of 10 greater than the buffer envelope
int bufEnvPrecisionDigits = (int) (Math.log(bufEnvMax) / Math.log(10) + 1.0);
int minUnitLog10 = maxPrecisionDigits - bufEnvPrecisionDigits;
double scaleFactor = Math.pow(10.0, minUnitLog10);
return scaleFactor;
}
/*
private static double OLDprecisionScaleFactor(Geometry g,
double distance,
int maxPrecisionDigits)
{
Envelope env = g.getEnvelopeInternal();
double envSize = Math.max(env.getHeight(), env.getWidth());
double expandByDistance = distance > 0.0 ? distance : 0.0;
double bufEnvSize = envSize + 2 * expandByDistance;
// the smallest power of 10 greater than the buffer envelope
int bufEnvLog10 = (int) (Math.log(bufEnvSize) / Math.log(10) + 1.0);
int minUnitLog10 = bufEnvLog10 - maxPrecisionDigits;
// scale factor is inverse of min Unit size, so flip sign of exponent
double scaleFactor = Math.pow(10.0, -minUnitLog10);
return scaleFactor;
}
*/
/**
* Computes the buffer of a geometry for a given buffer distance.
*
* @param g the geometry to buffer
* @param distance the buffer distance
* @return the buffer of the input geometry
*/
public static Geometry bufferOp(Geometry g, double distance)
{
BufferOp gBuf = new BufferOp(g);
Geometry geomBuf = gBuf.getResultGeometry(distance);
//BufferDebug.saveBuffer(geomBuf);
//BufferDebug.runCount++;
return geomBuf;
}
/**
* Comutes the buffer for a geometry for a given buffer distance
* and accuracy of approximation.
*
* @param g the geometry to buffer
* @param distance the buffer distance
* @param params the buffer parameters to use
* @return the buffer of the input geometry
*
*/
public static Geometry bufferOp(Geometry g, double distance, BufferParameters params)
{
BufferOp bufOp = new BufferOp(g, params);
Geometry geomBuf = bufOp.getResultGeometry(distance);
return geomBuf;
}
/**
* Comutes the buffer for a geometry for a given buffer distance
* and accuracy of approximation.
*
* @param g the geometry to buffer
* @param distance the buffer distance
* @param quadrantSegments the number of segments used to approximate a quarter circle
* @return the buffer of the input geometry
*
*/
public static Geometry bufferOp(Geometry g, double distance, int quadrantSegments)
{
BufferOp bufOp = new BufferOp(g);
bufOp.setQuadrantSegments(quadrantSegments);
Geometry geomBuf = bufOp.getResultGeometry(distance);
return geomBuf;
}
/**
* Comutes the buffer for a geometry for a given buffer distance
* and accuracy of approximation.
*
* @param g the geometry to buffer
* @param distance the buffer distance
* @param quadrantSegments the number of segments used to approximate a quarter circle
* @param endCapStyle the end cap style to use
* @return the buffer of the input geometry
*
*/
public static Geometry bufferOp(Geometry g,
double distance,
int quadrantSegments,
int endCapStyle)
{
BufferOp bufOp = new BufferOp(g);
bufOp.setQuadrantSegments(quadrantSegments);
bufOp.setEndCapStyle(endCapStyle);
Geometry geomBuf = bufOp.getResultGeometry(distance);
return geomBuf;
}
private Geometry argGeom;
private double distance;
private BufferParameters bufParams = new BufferParameters();
private Geometry resultGeometry = null;
private RuntimeException saveException; // debugging only
/**
* Initializes a buffer computation for the given geometry
*
* @param g the geometry to buffer
*/
public BufferOp(Geometry g) {
argGeom = g;
}
/**
* Initializes a buffer computation for the given geometry
* with the given set of parameters
*
* @param g the geometry to buffer
* @param bufParams the buffer parameters to use
*/
public BufferOp(Geometry g, BufferParameters bufParams) {
argGeom = g;
this.bufParams = bufParams;
}
/**
* Specifies the end cap style of the generated buffer.
* The styles supported are {@link BufferParameters#CAP_ROUND}, {@link BufferParameters##CAP_BUTT}, and {@link BufferParameters##CAP_SQUARE}.
* The default is CAP_ROUND.
*
* @param endCapStyle the end cap style to specify
*/
public void setEndCapStyle(int endCapStyle)
{
bufParams.setEndCapStyle(endCapStyle);
}
/**
* Sets the number of segments used to approximate a angle fillet
*
* @param quadrantSegments the number of segments in a fillet for a quadrant
*/
public void setQuadrantSegments(int quadrantSegments)
{
bufParams.setQuadrantSegments(quadrantSegments);
}
/**
* Returns the buffer computed for a geometry for a given buffer distance.
*
* @param distance the buffer distance
* @return the buffer of the input geometry
*/
public Geometry getResultGeometry(double distance)
{
this.distance = distance;
computeGeometry();
return resultGeometry;
}
private void computeGeometry()
{
bufferOriginalPrecision();
if (resultGeometry != null) return;
PrecisionModel argPM = argGeom.getFactory().getPrecisionModel();
if (argPM.getType() == PrecisionModel.FIXED)
bufferFixedPrecision(argPM);
else
bufferReducedPrecision();
}
private void bufferReducedPrecision()
{
// try and compute with decreasing precision
for (int precDigits = MAX_PRECISION_DIGITS; precDigits >= 0; precDigits--) {
try {
bufferReducedPrecision(precDigits);
}
catch (TopologyException ex) {
// update the saved exception to reflect the new input geometry
saveException = ex;
// don't propagate the exception - it will be detected by fact that resultGeometry is null
}
if (resultGeometry != null) return;
}
// tried everything - have to bail
throw saveException;
}
private void bufferOriginalPrecision()
{
try {
// use fast noding by default
BufferBuilder bufBuilder = new BufferBuilder(bufParams);
resultGeometry = bufBuilder.buffer(argGeom, distance);
}
catch (RuntimeException ex) {
saveException = ex;
// don't propagate the exception - it will be detected by fact that resultGeometry is null
// testing ONLY - propagate exception
//throw ex;
}
}
private void bufferReducedPrecision(int precisionDigits)
{
double sizeBasedScaleFactor = precisionScaleFactor(argGeom, distance, precisionDigits);
// System.out.println("recomputing with precision scale factor = " + sizeBasedScaleFactor);
PrecisionModel fixedPM = new PrecisionModel(sizeBasedScaleFactor);
bufferFixedPrecision(fixedPM);
}
private void bufferFixedPrecision(PrecisionModel fixedPM)
{
Noder noder = new ScaledNoder(new MCIndexSnapRounder(new PrecisionModel(1.0)),
fixedPM.getScale());
BufferBuilder bufBuilder = new BufferBuilder(bufParams);
bufBuilder.setWorkingPrecisionModel(fixedPM);
bufBuilder.setNoder(noder);
// this may throw an exception, if robustness errors are encountered
resultGeometry = bufBuilder.buffer(argGeom, distance);
}
}