213 lines
8.3 KiB
Python
213 lines
8.3 KiB
Python
# Needed ctypes routines
|
|
from ctypes import c_double, byref
|
|
|
|
# Other GDAL imports.
|
|
from django.contrib.gis.gdal.base import GDALBase
|
|
from django.contrib.gis.gdal.envelope import Envelope, OGREnvelope
|
|
from django.contrib.gis.gdal.error import OGRException, OGRIndexError, SRSException
|
|
from django.contrib.gis.gdal.feature import Feature
|
|
from django.contrib.gis.gdal.field import OGRFieldTypes
|
|
from django.contrib.gis.gdal.geomtype import OGRGeomType
|
|
from django.contrib.gis.gdal.geometries import OGRGeometry
|
|
from django.contrib.gis.gdal.srs import SpatialReference
|
|
|
|
# GDAL ctypes function prototypes.
|
|
from django.contrib.gis.gdal.prototypes import ds as capi, geom as geom_api, srs as srs_api
|
|
|
|
# For more information, see the OGR C API source code:
|
|
# http://www.gdal.org/ogr/ogr__api_8h.html
|
|
#
|
|
# The OGR_L_* routines are relevant here.
|
|
class Layer(GDALBase):
|
|
"A class that wraps an OGR Layer, needs to be instantiated from a DataSource object."
|
|
|
|
#### Python 'magic' routines ####
|
|
def __init__(self, layer_ptr, ds):
|
|
"""
|
|
Initializes on an OGR C pointer to the Layer and the `DataSource` object
|
|
that owns this layer. The `DataSource` object is required so that a
|
|
reference to it is kept with this Layer. This prevents garbage
|
|
collection of the `DataSource` while this Layer is still active.
|
|
"""
|
|
if not layer_ptr:
|
|
raise OGRException('Cannot create Layer, invalid pointer given')
|
|
self.ptr = layer_ptr
|
|
self._ds = ds
|
|
self._ldefn = capi.get_layer_defn(self._ptr)
|
|
# Does the Layer support random reading?
|
|
self._random_read = self.test_capability('RandomRead')
|
|
|
|
def __getitem__(self, index):
|
|
"Gets the Feature at the specified index."
|
|
if isinstance(index, (int, long)):
|
|
# An integer index was given -- we cannot do a check based on the
|
|
# number of features because the beginning and ending feature IDs
|
|
# are not guaranteed to be 0 and len(layer)-1, respectively.
|
|
if index < 0: raise OGRIndexError('Negative indices are not allowed on OGR Layers.')
|
|
return self._make_feature(index)
|
|
elif isinstance(index, slice):
|
|
# A slice was given
|
|
start, stop, stride = index.indices(self.num_feat)
|
|
return [self._make_feature(fid) for fid in xrange(start, stop, stride)]
|
|
else:
|
|
raise TypeError('Integers and slices may only be used when indexing OGR Layers.')
|
|
|
|
def __iter__(self):
|
|
"Iterates over each Feature in the Layer."
|
|
# ResetReading() must be called before iteration is to begin.
|
|
capi.reset_reading(self._ptr)
|
|
for i in xrange(self.num_feat):
|
|
yield Feature(capi.get_next_feature(self._ptr), self._ldefn)
|
|
|
|
def __len__(self):
|
|
"The length is the number of features."
|
|
return self.num_feat
|
|
|
|
def __str__(self):
|
|
"The string name of the layer."
|
|
return self.name
|
|
|
|
def _make_feature(self, feat_id):
|
|
"""
|
|
Helper routine for __getitem__ that constructs a Feature from the given
|
|
Feature ID. If the OGR Layer does not support random-access reading,
|
|
then each feature of the layer will be incremented through until the
|
|
a Feature is found matching the given feature ID.
|
|
"""
|
|
if self._random_read:
|
|
# If the Layer supports random reading, return.
|
|
try:
|
|
return Feature(capi.get_feature(self.ptr, feat_id), self._ldefn)
|
|
except OGRException:
|
|
pass
|
|
else:
|
|
# Random access isn't supported, have to increment through
|
|
# each feature until the given feature ID is encountered.
|
|
for feat in self:
|
|
if feat.fid == feat_id: return feat
|
|
# Should have returned a Feature, raise an OGRIndexError.
|
|
raise OGRIndexError('Invalid feature id: %s.' % feat_id)
|
|
|
|
#### Layer properties ####
|
|
@property
|
|
def extent(self):
|
|
"Returns the extent (an Envelope) of this layer."
|
|
env = OGREnvelope()
|
|
capi.get_extent(self.ptr, byref(env), 1)
|
|
return Envelope(env)
|
|
|
|
@property
|
|
def name(self):
|
|
"Returns the name of this layer in the Data Source."
|
|
return capi.get_fd_name(self._ldefn)
|
|
|
|
@property
|
|
def num_feat(self, force=1):
|
|
"Returns the number of features in the Layer."
|
|
return capi.get_feature_count(self.ptr, force)
|
|
|
|
@property
|
|
def num_fields(self):
|
|
"Returns the number of fields in the Layer."
|
|
return capi.get_field_count(self._ldefn)
|
|
|
|
@property
|
|
def geom_type(self):
|
|
"Returns the geometry type (OGRGeomType) of the Layer."
|
|
return OGRGeomType(capi.get_fd_geom_type(self._ldefn))
|
|
|
|
@property
|
|
def srs(self):
|
|
"Returns the Spatial Reference used in this Layer."
|
|
try:
|
|
ptr = capi.get_layer_srs(self.ptr)
|
|
return SpatialReference(srs_api.clone_srs(ptr))
|
|
except SRSException:
|
|
return None
|
|
|
|
@property
|
|
def fields(self):
|
|
"""
|
|
Returns a list of string names corresponding to each of the Fields
|
|
available in this Layer.
|
|
"""
|
|
return [capi.get_field_name(capi.get_field_defn(self._ldefn, i))
|
|
for i in xrange(self.num_fields) ]
|
|
|
|
@property
|
|
def field_types(self):
|
|
"""
|
|
Returns a list of the types of fields in this Layer. For example,
|
|
the list [OFTInteger, OFTReal, OFTString] would be returned for
|
|
an OGR layer that had an integer, a floating-point, and string
|
|
fields.
|
|
"""
|
|
return [OGRFieldTypes[capi.get_field_type(capi.get_field_defn(self._ldefn, i))]
|
|
for i in xrange(self.num_fields)]
|
|
|
|
@property
|
|
def field_widths(self):
|
|
"Returns a list of the maximum field widths for the features."
|
|
return [capi.get_field_width(capi.get_field_defn(self._ldefn, i))
|
|
for i in xrange(self.num_fields)]
|
|
|
|
@property
|
|
def field_precisions(self):
|
|
"Returns the field precisions for the features."
|
|
return [capi.get_field_precision(capi.get_field_defn(self._ldefn, i))
|
|
for i in xrange(self.num_fields)]
|
|
|
|
def _get_spatial_filter(self):
|
|
try:
|
|
return OGRGeometry(geom_api.clone_geom(capi.get_spatial_filter(self.ptr)))
|
|
except OGRException:
|
|
return None
|
|
|
|
def _set_spatial_filter(self, filter):
|
|
if isinstance(filter, OGRGeometry):
|
|
capi.set_spatial_filter(self.ptr, filter.ptr)
|
|
elif isinstance(filter, (tuple, list)):
|
|
if not len(filter) == 4:
|
|
raise ValueError('Spatial filter list/tuple must have 4 elements.')
|
|
# Map c_double onto params -- if a bad type is passed in it
|
|
# will be caught here.
|
|
xmin, ymin, xmax, ymax = map(c_double, filter)
|
|
capi.set_spatial_filter_rect(self.ptr, xmin, ymin, xmax, ymax)
|
|
elif filter is None:
|
|
capi.set_spatial_filter(self.ptr, None)
|
|
else:
|
|
raise TypeError('Spatial filter must be either an OGRGeometry instance, a 4-tuple, or None.')
|
|
|
|
spatial_filter = property(_get_spatial_filter, _set_spatial_filter)
|
|
|
|
#### Layer Methods ####
|
|
def get_fields(self, field_name):
|
|
"""
|
|
Returns a list containing the given field name for every Feature
|
|
in the Layer.
|
|
"""
|
|
if not field_name in self.fields:
|
|
raise OGRException('invalid field name: %s' % field_name)
|
|
return [feat.get(field_name) for feat in self]
|
|
|
|
def get_geoms(self, geos=False):
|
|
"""
|
|
Returns a list containing the OGRGeometry for every Feature in
|
|
the Layer.
|
|
"""
|
|
if geos:
|
|
from django.contrib.gis.geos import GEOSGeometry
|
|
return [GEOSGeometry(feat.geom.wkb) for feat in self]
|
|
else:
|
|
return [feat.geom for feat in self]
|
|
|
|
def test_capability(self, capability):
|
|
"""
|
|
Returns a bool indicating whether the this Layer supports the given
|
|
capability (a string). Valid capability strings include:
|
|
'RandomRead', 'SequentialWrite', 'RandomWrite', 'FastSpatialFilter',
|
|
'FastFeatureCount', 'FastGetExtent', 'CreateField', 'Transactions',
|
|
'DeleteFeature', and 'FastSetNextByIndex'.
|
|
"""
|
|
return bool(capi.test_capability(self.ptr, capability))
|