Computes the buffer of a geometry, for both positive and negative buffer distances. More...
#include <geos/opBuffer.h>
Public Types | |
enum | { CAP_ROUND = BufferParameters::CAP_ROUND, CAP_BUTT = BufferParameters::CAP_FLAT, CAP_SQUARE = BufferParameters::CAP_SQUARE } |
Public Member Functions | |
BufferOp (const geom::Geometry *g) | |
BufferOp (const geom::Geometry *g, const BufferParameters ¶ms) | |
void | setEndCapStyle (int nEndCapStyle) |
void | setQuadrantSegments (int nQuadrantSegments) |
geom::Geometry * | getResultGeometry (double nDistance) |
Static Public Member Functions | |
static geom::Geometry * | bufferOp (const geom::Geometry *g, double distance, int quadrantSegments=BufferParameters::DEFAULT_QUADRANT_SEGMENTS, int endCapStyle=BufferParameters::CAP_ROUND) |
Computes the buffer of a geometry, for both positive and negative buffer distances.
In GIS, the buffer of a geometry is defined as the Minkowski sum or difference of the geometry with a circle with radius equal to the absolute value of the buffer distance. In the CAD/CAM world buffers are known as offset curves. In morphological analysis they are known 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 can only be approximations to the true geometry. The user can control the accuracy of the curve approximation by specifying the number of linear segments with which to approximate a curve.
The end cap style of a linear buffer may be specified. The following end cap styles are supported:
anonymous enum |
geos::operation::buffer::BufferOp::BufferOp | ( | const geom::Geometry * | g | ) | [inline] |
Initializes a buffer computation for the given geometry
g | the geometry to buffer |
geos::operation::buffer::BufferOp::BufferOp | ( | const geom::Geometry * | g, | |
const BufferParameters & | params | |||
) | [inline] |
Initializes a buffer computation for the given geometry with the given set of parameters
g | the geometry to buffer | |
params | the buffer parameters to use. This class will copy it to private memory. |
static geom::Geometry* geos::operation::buffer::BufferOp::bufferOp | ( | const geom::Geometry * | g, | |
double | distance, | |||
int | quadrantSegments = BufferParameters::DEFAULT_QUADRANT_SEGMENTS , |
|||
int | endCapStyle = BufferParameters::CAP_ROUND | |||
) | [static] |
Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.
g | the geometry to buffer | |
distance | the buffer distance | |
quadrantSegments | the number of segments used to approximate a quarter circle |
geom::Geometry* geos::operation::buffer::BufferOp::getResultGeometry | ( | double | nDistance | ) |
Returns the buffer computed for a geometry for a given buffer distance.
g | the geometry to buffer | |
distance | the buffer distance |
void geos::operation::buffer::BufferOp::setEndCapStyle | ( | int | nEndCapStyle | ) | [inline] |
Specifies the end cap style of the generated buffer. The styles supported are CAP_ROUND, CAP_BUTT, and CAP_SQUARE. The default is CAP_ROUND.
endCapStyle | the end cap style to specify |
References geos::operation::buffer::BufferParameters::setEndCapStyle().
void geos::operation::buffer::BufferOp::setQuadrantSegments | ( | int | nQuadrantSegments | ) | [inline] |
Specifies the end cap style of the generated buffer. The styles supported are CAP_ROUND, CAP_BUTT, and CAP_SQUARE. The default is CAP_ROUND.
endCapStyle | the end cap style to specify |
References geos::operation::buffer::BufferParameters::setQuadrantSegments().