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gis: added the Envelope class, used in getting layer and geometry extents; also added boundary and convex_hull properties.
git-svn-id: http://code.djangoproject.com/svn/django/branches/gis@5527 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Justin Bronn
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112
django/contrib/gis/gdal/Envelope.py
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112
django/contrib/gis/gdal/Envelope.py
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@ -0,0 +1,112 @@
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from ctypes import Structure, c_double
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from types import TupleType
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"""
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The GDAL/OGR library uses an Envelope structure to hold the bounding
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box information for a geometry. The envelope (bounding box) contains
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two pairs of coordinates, one for the lower left coordinate and one
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for the upper right coordinate:
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+----------o Upper right; (max_x, max_y)
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Lower left (min_x, min_y) o----------+
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"""
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# The OGR definition of an Envelope is a C structure containing four doubles.
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# See the 'ogr_core.h' source file for more information:
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# http://www.gdal.org/ogr/ogr__core_8h-source.html
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class OGREnvelope(Structure):
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"Represents the OGREnvelope C Structure."
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_fields_ = [("MinX", c_double),
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("MaxX", c_double),
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("MinY", c_double),
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("MaxY", c_double),
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]
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class Envelope(object):
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"A class that will wrap an OGR Envelope structure."
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def __init__(self, *args):
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if len(args) == 1:
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if isinstance(args[0], OGREnvelope):
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# OGREnvelope (a ctypes Structure) was passed in.
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self._envelope = args[0]
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elif isinstance(args[0], TupleType) and len(args[0]) == 4:
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# A Tuple was passed in
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self._from_tuple(args[0])
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else:
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raise OGRException, 'Incorrect type of argument: %s' % str(type(args[0]))
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elif len(args) == 4:
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self._from_tuple(args)
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else:
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raise OGRException, 'Incorrect number of arguments!'
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def __eq__(self, other):
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"Returns true if the envelopes are equivalent; can compare against other Envelopes and 4-tuples."
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if isinstance(other, Envelope):
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return (self.min_x == other.min_x) and (self.min_y == other.min_y) and \
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(self.max_x == other.max_x) and (self.max_y == other.max_y)
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elif isinstance(other, TupleType) and len(other) == 4:
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return (self.min_x == other[0]) and (self.min_y == other[1]) and \
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(self.max_x == other[2]) and (self.max_y == other[3])
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else:
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raise OGRException, 'Equivalence testing only works with other Envelopes.'
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def __str__(self):
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"Returns a string representation of the tuple."
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return str(self.tuple)
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def _from_tuple(self, tup):
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"Initializes the C OGR Envelope structure from the given tuple."
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self._envelope = OGREnvelope()
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self._envelope.MinX = tup[0]
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self._envelope.MinY = tup[1]
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self._envelope.MaxX = tup[2]
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self._envelope.MaxY = tup[3]
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@property
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def min_x(self):
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"Returns the value of the minimum X coordinate."
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return self._envelope.MinX
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@property
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def min_y(self):
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"Returns the value of the minimum Y coordinate."
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return self._envelope.MinY
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@property
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def max_x(self):
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"Returns the value of the maximum X coordinate."
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return self._envelope.MaxX
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@property
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def max_y(self):
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"Returns the value of the maximum Y coordinate."
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return self._envelope.MaxY
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@property
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def ur(self):
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"Returns the upper-right coordinate."
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return (self.max_x, self.max_y)
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@property
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def ll(self):
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"Returns the lower-left coordinate."
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return (self.min_x, self.min_y)
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@property
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def tuple(self):
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"Returns a tuple representing the envelope."
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return (self.min_x, self.min_y, self.max_x, self.max_y)
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@property
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def wkt(self):
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"Returns WKT representing a Polygon for this envelope."
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# TODO: Fix significant figures.
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return 'POLYGON((%f %f,%f %f,%f %f,%f %f,%f %f))' % (self.min_x, self.min_y, self.min_x, self.max_y,
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self.max_x, self.max_y, self.max_x, self.min_y,
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self.min_x, self.min_y)
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@ -1,12 +1,13 @@
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# Needed ctypes routines
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from ctypes import c_int, c_long, c_void_p, string_at
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from ctypes import c_int, c_long, c_void_p, byref, string_at
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# The GDAL C Library
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from django.contrib.gis.gdal.libgdal import lgdal
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# Other GDAL imports.
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from django.contrib.gis.gdal.Envelope import Envelope, OGREnvelope
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from django.contrib.gis.gdal.Feature import Feature
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from django.contrib.gis.gdal.OGRError import OGRException
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from django.contrib.gis.gdal.OGRError import OGRException, check_err
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from django.contrib.gis.gdal.SpatialReference import SpatialReference
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# For more information, see the OGR C API source code:
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@ -57,6 +58,13 @@ class Layer(object):
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return self.name
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#### Layer properties ####
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@property
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def extent(self):
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"Returns the extent (an Envelope) of this layer."
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env = OGREnvelope()
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check_err(lgdal.OGR_L_GetExtent(self._layer, byref(env), c_int(1)))
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return Envelope(env)
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@property
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def name(self):
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"Returns the name of this layer in the Data Source."
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@ -4,6 +4,7 @@ from ctypes import byref, string_at, c_char_p, c_double, c_int, c_void_p
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# Getting the GDAL C library and error checking facilities
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from django.contrib.gis.gdal.libgdal import lgdal
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from django.contrib.gis.gdal.Envelope import Envelope, OGREnvelope
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from django.contrib.gis.gdal.OGRError import check_err, OGRException
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from django.contrib.gis.gdal.SpatialReference import SpatialReference, CoordTransform
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@ -249,6 +250,13 @@ class OGRGeometry(object):
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a = lgdal.OGR_G_GetArea(self._g)
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return a.value
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@property
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def envelope(self):
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"Returns the envelope for this Geometry."
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env = OGREnvelope()
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lgdal.OGR_G_GetEnvelope(self._g, byref(env))
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return Envelope(env)
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#### Geometry Methods ####
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def clone(self):
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"Clones this OGR Geometry."
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@ -322,10 +330,22 @@ class OGRGeometry(object):
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return self._topology(lgdal.OGR_G_Overlaps, other)
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#### Geometry-generation Methods ####
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def _geomgen(self, gen_func, other):
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if not isinstance(other, OGRGeometry):
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raise OGRException, 'Must use another OGRGeometry object for geometry-generating operations!'
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return OGRGeometry(gen_func(self._g, other._g))
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def _geomgen(self, gen_func, other=None):
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"A helper routine for the OGR routines that generate geometries."
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if isinstance(other, OGRGeometry):
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return OGRGeometry(gen_func(self._g, other._g))
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else:
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return OGRGeometry(gen_func(self._g))
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@property
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def boundary(self):
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"Returns the boundary of this geometry."
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return self._geomgen(lgdal.OGR_G_GetBoundary)
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@property
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def convex_hull(self):
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"Returns the smallest convex Polygon that contains all the points in the Geometry."
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return self._geomgen(lgdal.OGR_G_ConvexHull)
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def union(self, other):
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"""Returns a new geometry consisting of the region which is the union of
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@ -1,4 +1,5 @@
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from Driver import Driver
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from Envelope import Envelope
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from DataSource import DataSource
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from SpatialReference import SpatialReference, CoordTransform
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from OGRGeometry import OGRGeometry, OGRGeomType
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@ -1,5 +1,6 @@
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import os, os.path, unittest
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from django.contrib.gis.gdal import DataSource, OGRException
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from django.contrib.gis.gdal.Envelope import Envelope
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from django.contrib.gis.gdal.Field import OFTReal, OFTInteger, OFTString
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# Path for SHP files
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@ -16,8 +17,10 @@ class TestSHP:
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# List of acceptable data sources.
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ds_list = (TestSHP('test_point', nfeat=5, nfld=3, geom='POINT', gtype=1, fields={'dbl' : OFTReal, 'int' : OFTReal, 'str' : OFTString,},
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extent=(-1.35011,0.166623,-0.524093,0.824508), # Got extent from QGIS
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srs_wkt='GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]'),
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TestSHP('test_poly', nfeat=3, nfld=3, geom='POLYGON', gtype=3, fields={'float' : OFTReal, 'int' : OFTReal, 'str' : OFTString,},
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extent=(-1.01513,-0.558245,0.161876,0.839637), # Got extent from QGIS
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srs_wkt='GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]'),
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)
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@ -67,8 +70,15 @@ class DataSourceTest(unittest.TestCase):
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self.assertEqual(len(layer), source.nfeat)
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# Making sure we get the number of fields we expect
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self.assertEqual(layer.num_fields, source.nfld)
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self.assertEqual(len(layer.fields), source.nfld)
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self.assertEqual(source.nfld, layer.num_fields)
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self.assertEqual(source.nfld, len(layer.fields))
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# Testing the layer's extent (an Envelope), and it's properties
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self.assertEqual(True, isinstance(layer.extent, Envelope))
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self.assertAlmostEqual(source.extent[0], layer.extent.min_x, 5)
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self.assertAlmostEqual(source.extent[1], layer.extent.min_y, 5)
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self.assertAlmostEqual(source.extent[2], layer.extent.max_x, 5)
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self.assertAlmostEqual(source.extent[3], layer.extent.max_y, 5)
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# Now checking the field names.
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flds = layer.fields
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