Class BufferOp

java.lang.Object
org.locationtech.jts.operation.buffer.BufferOp

public class BufferOp extends Object
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 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 BufferParameters.setQuadrantSegments(int) or setQuadrantSegments(int).

The end cap style of a linear buffer may be specified. The following end cap styles are supported:

The join style of the corners in a buffer may be specified. The following join styles are supported:

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 specified, with a 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
  • Field Details

    • CAP_ROUND

      public static final int CAP_ROUND
      Deprecated.
      use BufferParameters
      Specifies a round line buffer end cap style.
      See Also:
    • CAP_BUTT

      public static final int CAP_BUTT
      Deprecated.
      use BufferParameters
      Specifies a butt (or flat) line buffer end cap style.
      See Also:
    • CAP_FLAT

      public static final int CAP_FLAT
      Deprecated.
      use BufferParameters
      Specifies a butt (or flat) line buffer end cap style.
      See Also:
    • CAP_SQUARE

      public static final int CAP_SQUARE
      Deprecated.
      use BufferParameters
      Specifies a square line buffer end cap style.
      See Also:
    • MAX_PRECISION_DIGITS

      private static int MAX_PRECISION_DIGITS
      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).
    • argGeom

      private Geometry argGeom
    • distance

      private double distance
    • bufParams

      private BufferParameters bufParams
    • resultGeometry

      private Geometry resultGeometry
    • saveException

      private RuntimeException saveException
  • Constructor Details

    • BufferOp

      public BufferOp(Geometry g)
      Initializes a buffer computation for the given geometry
      Parameters:
      g - the geometry to buffer
    • BufferOp

      public BufferOp(Geometry g, BufferParameters bufParams)
      Initializes a buffer computation for the given geometry with the given set of parameters
      Parameters:
      g - the geometry to buffer
      bufParams - the buffer parameters to use
  • Method Details

    • precisionScaleFactor

      private static double precisionScaleFactor(Geometry g, double distance, int maxPrecisionDigits)
      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.

      Parameters:
      g - the Geometry being buffered
      distance - the buffer distance
      maxPrecisionDigits - the max # of digits that should be allowed by the precision determined by the computed scale factor
      Returns:
      a scale factor for the buffer computation
    • bufferOp

      public static Geometry bufferOp(Geometry g, double distance)
      Computes the buffer of a geometry for a given buffer distance.
      Parameters:
      g - the geometry to buffer
      distance - the buffer distance
      Returns:
      the buffer of the input geometry
    • bufferOp

      public static Geometry bufferOp(Geometry g, double distance, BufferParameters params)
      Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.
      Parameters:
      g - the geometry to buffer
      distance - the buffer distance
      params - the buffer parameters to use
      Returns:
      the buffer of the input geometry
    • bufferOp

      public static Geometry bufferOp(Geometry g, double distance, int quadrantSegments)
      Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.
      Parameters:
      g - the geometry to buffer
      distance - the buffer distance
      quadrantSegments - the number of segments used to approximate a quarter circle
      Returns:
      the buffer of the input geometry
    • bufferOp

      public static Geometry bufferOp(Geometry g, double distance, int quadrantSegments, int endCapStyle)
      Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.
      Parameters:
      g - the geometry to buffer
      distance - the buffer distance
      quadrantSegments - the number of segments used to approximate a quarter circle
      endCapStyle - the end cap style to use
      Returns:
      the buffer of the input geometry
    • setEndCapStyle

      public void setEndCapStyle(int endCapStyle)
      Specifies the end cap style of the generated buffer. The styles supported are BufferParameters.CAP_ROUND, BufferParameters.CAP_FLAT, and BufferParameters.CAP_SQUARE. The default is CAP_ROUND.
      Parameters:
      endCapStyle - the end cap style to specify
    • setQuadrantSegments

      public void setQuadrantSegments(int quadrantSegments)
      Sets the number of segments used to approximate a angle fillet
      Parameters:
      quadrantSegments - the number of segments in a fillet for a quadrant
    • getResultGeometry

      public Geometry getResultGeometry(double distance)
      Returns the buffer computed for a geometry for a given buffer distance.
      Parameters:
      distance - the buffer distance
      Returns:
      the buffer of the input geometry
    • computeGeometry

      private void computeGeometry()
    • bufferReducedPrecision

      private void bufferReducedPrecision()
    • bufferOriginalPrecision

      private void bufferOriginalPrecision()
    • bufferReducedPrecision

      private void bufferReducedPrecision(int precisionDigits)
    • bufferFixedPrecision

      private void bufferFixedPrecision(PrecisionModel fixedPM)