Class BufferOp


  • public class BufferOp
    extends java.lang.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 Detail

      • CAP_ROUND

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

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

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

        public static final int CAP_SQUARE
        Deprecated.
        use BufferParameters
        Specifies a square line buffer end cap style.
        See Also:
        Constant Field Values
      • 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).
      • distance

        private double distance
      • resultGeometry

        private Geometry resultGeometry
      • saveException

        private java.lang.RuntimeException saveException
    • Constructor Detail

      • 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 Detail

      • 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
      • 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)