Python base.geom_factory函数代码示例

    def polygonize_full(self, lines):
        """Creates polygons from a source of lines, returning the polygons
        and leftover geometries.

        The source may be a MultiLineString, a sequence of LineString objects,
        or a sequence of objects than can be adapted to LineStrings.

        Returns a tuple of objects: (polygons, dangles, cut edges, invalid ring
        lines). Each are a geometry collection.

        Dangles are edges which have one or both ends which are not incident on
        another edge endpoint. Cut edges are connected at both ends but do not
        form part of polygon. Invalid ring lines form rings which are invalid
        (bowties, etc).
        """
        source = getattr(lines, "geoms", None) or lines
        try:
            source = iter(source)
        except TypeError:
            source = [source]
        finally:
            obs = [self.shapeup(l) for l in source]
        L = len(obs)
        subs = (c_void_p * L)()
        for i, g in enumerate(obs):
            subs[i] = g._geom
        collection = lgeos.GEOSGeom_createCollection(5, subs, L)
        dangles = c_void_p()
        cuts = c_void_p()
        invalids = c_void_p()
        product = lgeos.GEOSPolygonize_full(collection, byref(dangles), byref(cuts), byref(invalids))
        return (geom_factory(product), geom_factory(dangles), geom_factory(cuts), geom_factory(invalids))

def polygonize(iterator):
    """Creates polygons from a list of LineString objects.
    """
    lines = [shapeup(ob) for ob in iterator]
    geom_array_type = c_void_p * len(lines)
    geom_array = geom_array_type()
    for i, line in enumerate(lines):
        geom_array[i] = line._geom
    product = lgeos.GEOSPolygonize(byref(geom_array), len(lines))
    collection = geom_factory(product)
    for g in collection.geoms:
        clone = lgeos.GEOSGeom_clone(g._geom)
        g = geom_factory(clone)
        g._owned = False
        yield g

def clip_by_rect(geom, xmin, ymin, xmax, ymax):
    """Returns the portion of a geometry within a rectangle

    The geometry is clipped in a fast but possibly dirty way. The output is
    not guaranteed to be valid. No exceptions will be raised for topological
    errors.

    Parameters
    ----------
    geom : geometry
        The geometry to be clipped
    xmin : float
        Minimum x value of the rectangle
    ymin : float
        Minimum y value of the rectangle
    xmax : float
        Maximum x value of the rectangle
    ymax : float
        Maximum y value of the rectangle

    Notes
    -----
    Requires GEOS >= 3.5.0
    New in 1.7.
    """
    if geom.is_empty:
        return geom
    result = geom_factory(lgeos.methods['clip_by_rect'](geom._geom, xmin, ymin, xmax, ymax))
    return result

    def parallel_offset(
            self, distance, side='right',
            resolution=16, join_style=JOIN_STYLE.round, mitre_limit=5.0):

        """Returns a LineString or MultiLineString geometry at a distance from
        the object on its right or its left side.

        The side parameter may be 'left' or 'right' (default is 'right'). The
        resolution of the buffer around each vertex of the object increases by
        increasing the resolution keyword parameter or third positional
        parameter. If the distance parameter is negative the side is inverted,
        e.g. distance=5.0, side='left' is the same as distance=-5.0,
        side='right'.

        The join style is for outside corners between line segments. Accepted
        values are JOIN_STYLE.round (1), JOIN_STYLE.mitre (2), and
        JOIN_STYLE.bevel (3).

        The mitre ratio limit is used for very sharp corners. It is the ratio
        of the distance from the corner to the end of the mitred offset corner.
        When two line segments meet at a sharp angle, a miter join will extend
        far beyond the original geometry. To prevent unreasonable geometry, the
        mitre limit allows controlling the maximum length of the join corner.
        Corners with a ratio which exceed the limit will be beveled."""
        if mitre_limit == 0.0:
            raise ValueError(
                'Cannot compute offset from zero-length line segment')
        try:
            return geom_factory(self.impl['parallel_offset'](
                self, distance, resolution, join_style, mitre_limit, side))
        except OSError:
            raise TopologicalError()

def dumps(ob, hex=False, srid=None, **kw):
    """Dump a WKB representation of a geometry to a byte string, or a
    hex-encoded string if ``hex=True``.
    
    Parameters
    ----------
    ob : geometry
        The geometry to export to well-known binary (WKB) representation
    hex : bool
        If true, export the WKB as a hexidecimal string. The default is to
        return a binary string/bytes object.
    srid : int
        Spatial reference system ID to include in the output. The default value
        means no SRID is included.
    **kw : kwargs
        See available keyword output settings in ``shapely.geos.WKBWriter``."""
    if srid is not None:
        # clone the object and set the SRID before dumping
        geom = lgeos.GEOSGeom_clone(ob._geom)
        lgeos.GEOSSetSRID(geom, srid)
        ob = geom_factory(geom)
        kw["include_srid"] = True
    writer = WKBWriter(lgeos, **kw)
    if hex:
        return writer.write_hex(ob)
    else:
        return writer.write(ob)

def loads(data):
    """Load a geometry from a WKT string."""
    from shapely.geometry.base import geom_factory
    geom = lgeos.GEOSGeomFromWKT(c_char_p(data.encode('utf-8')))
    if not geom:
        raise ReadingError("Could not create geometry because of errors while reading input.")
    return geom_factory(geom)

    def parallel_offset(self, distance, side, resolution=16, join_style=1, mitre_limit=1.0):

        """Returns a LineString or MultiLineString geometry at a distance from
        the object on its right or its left side.
        
        Distance must be a positive float value. The side parameter may be
        'left' or 'right'. The resolution of the buffer around each vertex of
        the object increases by increasing the resolution keyword parameter or
        third positional parameter.
        
        The join style is for outside corners between line segments. Accepted
        values are 1 => ROUND, 2 => MITRE, 3 => BEVEL.
        
        The mitre ratio limit is used for very sharp corners. It is the ratio
        of the distance from the corner to the end of the mitred offset corner.
        When two line segments meet at a sharp angle, a miter join will extend
        far beyond the original geometry. To prevent unreasonable geometry, the
        mitre limit allows controlling the maximum length of the join corner.
        Corners with a ratio which exceed the limit will be beveled."""

        try:
            return geom_factory(
                self.impl["parallel_offset"](self, distance, resolution, join_style, mitre_limit, bool(side == "left"))
            )
        except WindowsError:
            raise TopologicalError()

def snap(g1, g2, tolerance):
    """Snap one geometry to another with a given tolerance

    Vertices of the first geometry are snapped to vertices of the second
    geometry. The resulting snapped geometry is returned. The input geometries
    are not modified.

    Parameters
    ----------
    g1 : geometry
        The first geometry
    g2 : geometry
        The second geometry
    tolerence : float
        The snapping tolerance

    Example
    -------
    >>> square = Polygon([(1,1), (2, 1), (2, 2), (1, 2), (1, 1)])
    >>> line = LineString([(0,0), (0.8, 0.8), (1.8, 0.95), (2.6, 0.5)])
    >>> result = snap(line, square, 0.5)
    >>> result.wkt
    'LINESTRING (0 0, 1 1, 2 1, 2.6 0.5)'
    """
    return(geom_factory(lgeos.methods['snap'](g1._geom, g2._geom, tolerance)))

def loads(data):
    """Load a geometry from a WKT string."""
    geom = lgeos.GEOSGeomFromWKT(c_char_p(data))
    if not geom:
        raise ReadingError, \
        "Could not create geometry because of errors while reading input."
    return geom_factory(geom)

def linemerge(shape):
    """ Returns a geometry with lines merged using GEOSLineMerge.
    """
    if shape.type != 'MultiLineString':
        return shape
    
    # copied from shapely.ops.linemerge at http://github.com/sgillies/shapely
    result = lgeos.GEOSLineMerge(shape._geom)
    return geom_factory(result)

 def polygonize(self, lines):
     """Creates polygons from a source of lines
     
     The source may be a MultiLineString, a sequence of LineString objects,
     or a sequence of objects than can be adapted to LineStrings.
     """
     source = getattr(lines, 'geoms', None) or lines
     obs = [self.shapeup(l) for l in source]
     geom_array_type = c_void_p * len(obs)
     geom_array = geom_array_type()
     for i, line in enumerate(obs):
         geom_array[i] = line._geom
     product = lgeos.GEOSPolygonize(byref(geom_array), len(obs))
     collection = geom_factory(product)
     for g in collection.geoms:
         clone = lgeos.GEOSGeom_clone(g._geom)
         g = geom_factory(clone)
         g._owned = False
         yield g

 def read(self, text):
     """Returns geometry from WKT"""
     if sys.version_info[0] >= 3:
         text = text.encode('ascii')
     geom = self._lgeos.GEOSWKTReader_read(self._reader, c_char_p(text))
     if not geom:
         raise ReadingError("Could not create geometry because of errors "
                            "while reading input.")
     # avoid circular import dependency
     from shapely.geometry.base import geom_factory
     return geom_factory(geom)

 def unary_union(self, geoms):
     """Returns the union of a sequence of geometries
     
     This is the most efficient method of dissolving many polygons.
     """
     L = len(geoms)
     subs = (c_void_p * L)()
     for i, g in enumerate(geoms):
         subs[i] = g._geom
     collection = lgeos.GEOSGeom_createCollection(6, subs, L)
     return geom_factory(lgeos.GEOSUnaryUnion(collection))

    def unary_union(self, geoms):
        """Returns the union of a sequence of geometries

        This method replaces :meth:`cascaded_union` as the
        prefered method for dissolving many polygons.

        """
        L = len(geoms)
        subs = (c_void_p * L)()
        for i, g in enumerate(geoms):
            subs[i] = g._geom
        collection = lgeos.GEOSGeom_createCollection(6, subs, L)
        return geom_factory(lgeos.methods['unary_union'](collection))

 def read(self, text):
     """Returns geometry from WKT"""
     if not isinstance(text, text_types):
         raise TypeError("Only str is accepted.")
     if sys.version_info[0] >= 3:
          text = text.encode()
     c_string = c_char_p(text)
     geom = self._lgeos.GEOSWKTReader_read(self._reader, c_string)
     if not geom:
         raise WKTReadingError(
             "Could not create geometry because of errors "
             "while reading input.")
     # avoid circular import dependency
     from shapely.geometry.base import geom_factory
     return geom_factory(geom)