243 lines
6.4 KiB
Python
243 lines
6.4 KiB
Python
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"""Points and related utilities
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"""
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from ctypes import c_double
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from shapely.errors import DimensionError
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from shapely.geos import lgeos
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from shapely.geometry.base import BaseGeometry, geos_geom_from_py
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from shapely.geometry.proxy import CachingGeometryProxy
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__all__ = ['Point', 'asPoint']
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class Point(BaseGeometry):
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"""
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A zero dimensional feature
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A point has zero length and zero area.
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Attributes
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----------
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x, y, z : float
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Coordinate values
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Example
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-------
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>>> p = Point(1.0, -1.0)
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>>> print(p)
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POINT (1.0000000000000000 -1.0000000000000000)
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>>> p.y
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-1.0
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>>> p.x
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1.0
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"""
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def __init__(self, *args):
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"""
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Parameters
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----------
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There are 2 cases:
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1) 1 parameter: this must satisfy the numpy array protocol.
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2) 2 or more parameters: x, y, z : float
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Easting, northing, and elevation.
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"""
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BaseGeometry.__init__(self)
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if len(args) > 0:
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self._set_coords(*args)
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# Coordinate getters and setters
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@property
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def x(self):
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"""Return x coordinate."""
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return self.coords[0][0]
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@property
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def y(self):
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"""Return y coordinate."""
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return self.coords[0][1]
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@property
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def z(self):
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"""Return z coordinate."""
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if self._ndim != 3:
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raise DimensionError("This point has no z coordinate.")
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return self.coords[0][2]
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@property
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def __geo_interface__(self):
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return {
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'type': 'Point',
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'coordinates': self.coords[0]
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}
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def svg(self, scale_factor=1., fill_color=None):
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"""Returns SVG circle element for the Point geometry.
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Parameters
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==========
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scale_factor : float
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Multiplication factor for the SVG circle diameter. Default is 1.
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fill_color : str, optional
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Hex string for fill color. Default is to use "#66cc99" if
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geometry is valid, and "#ff3333" if invalid.
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"""
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if self.is_empty:
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return '<g />'
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if fill_color is None:
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fill_color = "#66cc99" if self.is_valid else "#ff3333"
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return (
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'<circle cx="{0.x}" cy="{0.y}" r="{1}" '
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'stroke="#555555" stroke-width="{2}" fill="{3}" opacity="0.6" />'
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).format(self, 3. * scale_factor, 1. * scale_factor, fill_color)
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@property
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def ctypes(self):
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if not self._ctypes_data:
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array_type = c_double * self._ndim
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array = array_type()
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xy = self.coords[0]
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array[0] = xy[0]
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array[1] = xy[1]
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if self._ndim == 3:
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array[2] = xy[2]
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self._ctypes_data = array
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return self._ctypes_data
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def array_interface(self):
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"""Provide the Numpy array protocol."""
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if self.is_empty:
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ai = {'version': 3, 'typestr': '<f8', 'shape': (0,), 'data': (c_double * 0)()}
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else:
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ai = self.array_interface_base
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ai.update({'shape': (self._ndim,)})
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return ai
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__array_interface__ = property(array_interface)
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@property
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def bounds(self):
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"""Returns minimum bounding region (minx, miny, maxx, maxy)"""
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try:
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xy = self.coords[0]
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except IndexError:
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return ()
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return (xy[0], xy[1], xy[0], xy[1])
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# Coordinate access
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def _set_coords(self, *args):
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self.empty()
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if len(args) == 1:
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self._geom, self._ndim = geos_point_from_py(args[0])
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elif len(args) > 3:
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raise TypeError("Point() takes at most 3 arguments ({} given)".format(len(args)))
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else:
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self._geom, self._ndim = geos_point_from_py(tuple(args))
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coords = property(BaseGeometry._get_coords, _set_coords)
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@property
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def xy(self):
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"""Separate arrays of X and Y coordinate values
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Example:
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>>> x, y = Point(0, 0).xy
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>>> list(x)
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[0.0]
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>>> list(y)
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[0.0]
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"""
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return self.coords.xy
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class PointAdapter(CachingGeometryProxy, Point):
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_other_owned = False
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def __init__(self, context):
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self.context = context
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self.factory = geos_point_from_py
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@property
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def _ndim(self):
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try:
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# From array protocol
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array = self.context.__array_interface__
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n = array['shape'][0]
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assert n == 2 or n == 3
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return n
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except AttributeError:
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# Fall back on list
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return len(self.context)
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@property
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def __array_interface__(self):
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"""Provide the Numpy array protocol."""
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try:
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return self.context.__array_interface__
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except AttributeError:
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return self.array_interface()
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_get_coords = BaseGeometry._get_coords
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def _set_coords(self, ob):
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raise NotImplementedError("Adapters can not modify their sources")
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coords = property(_get_coords)
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def asPoint(context):
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"""Adapt an object to the Point interface"""
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return PointAdapter(context)
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def geos_point_from_py(ob, update_geom=None, update_ndim=0):
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"""Create a GEOS geom from an object that is a Point, a coordinate sequence
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or that provides the array interface.
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Returns the GEOS geometry and the number of its dimensions.
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"""
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if isinstance(ob, Point):
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return geos_geom_from_py(ob)
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# Accept either (x, y) or [(x, y)]
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if not hasattr(ob, '__getitem__'): # Iterators, e.g. Python 3 zip
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ob = list(ob)
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if isinstance(ob[0], tuple):
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coords = ob[0]
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else:
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coords = ob
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n = len(coords)
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dx = c_double(coords[0])
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dy = c_double(coords[1])
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dz = None
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if n == 3:
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dz = c_double(coords[2])
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if update_geom:
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cs = lgeos.GEOSGeom_getCoordSeq(update_geom)
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if n != update_ndim:
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raise ValueError(
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"Wrong coordinate dimensions; this geometry has dimensions: "
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"%d" % update_ndim)
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else:
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cs = lgeos.GEOSCoordSeq_create(1, n)
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# Because of a bug in the GEOS C API, always set X before Y
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lgeos.GEOSCoordSeq_setX(cs, 0, dx)
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lgeos.GEOSCoordSeq_setY(cs, 0, dy)
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if n == 3:
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lgeos.GEOSCoordSeq_setZ(cs, 0, dz)
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if update_geom:
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return None
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else:
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return lgeos.GEOSGeom_createPoint(cs), n
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def update_point_from_py(geom, ob):
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geos_point_from_py(ob, geom._geom, geom._ndim)
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