author | Sverre Rabbelier <srabbelier@gmail.com> |
Sat, 21 Feb 2009 21:56:55 +0000 | |
changeset 1446 | bcbbcb72429d |
parent 323 | ff1a9aa48cfd |
permissions | -rw-r--r-- |
323
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Load ../vendor/django into trunk/app/django.
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1 |
# Needed ctypes routines |
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2 |
from ctypes import byref |
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3 |
|
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4 |
# Other GDAL imports. |
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5 |
from django.contrib.gis.gdal.envelope import Envelope, OGREnvelope |
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from django.contrib.gis.gdal.error import OGRException, OGRIndexError, SRSException |
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7 |
from django.contrib.gis.gdal.feature import Feature |
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8 |
from django.contrib.gis.gdal.field import FIELD_CLASSES |
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9 |
from django.contrib.gis.gdal.geometries import OGRGeomType |
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10 |
from django.contrib.gis.gdal.srs import SpatialReference |
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11 |
|
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12 |
# GDAL ctypes function prototypes. |
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13 |
from django.contrib.gis.gdal.prototypes.ds import \ |
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14 |
get_extent, get_fd_geom_type, get_fd_name, get_feature, get_feature_count, \ |
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15 |
get_field_count, get_field_defn, get_field_name, get_field_precision, \ |
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16 |
get_field_width, get_field_type, get_layer_defn, get_layer_srs, \ |
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17 |
get_next_feature, reset_reading, test_capability |
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18 |
from django.contrib.gis.gdal.prototypes.srs import clone_srs |
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19 |
|
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20 |
# For more information, see the OGR C API source code: |
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21 |
# http://www.gdal.org/ogr/ogr__api_8h.html |
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22 |
# |
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23 |
# The OGR_L_* routines are relevant here. |
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24 |
class Layer(object): |
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25 |
"A class that wraps an OGR Layer, needs to be instantiated from a DataSource object." |
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26 |
|
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27 |
#### Python 'magic' routines #### |
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28 |
def __init__(self, layer_ptr): |
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29 |
"Needs a C pointer (Python/ctypes integer) in order to initialize." |
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self._ptr = None # Initially NULL |
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31 |
if not layer_ptr: |
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32 |
raise OGRException('Cannot create Layer, invalid pointer given') |
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self._ptr = layer_ptr |
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34 |
self._ldefn = get_layer_defn(self._ptr) |
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35 |
# Does the Layer support random reading? |
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36 |
self._random_read = self.test_capability('RandomRead') |
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37 |
|
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38 |
def __getitem__(self, index): |
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39 |
"Gets the Feature at the specified index." |
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40 |
if isinstance(index, (int, long)): |
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41 |
# An integer index was given -- we cannot do a check based on the |
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42 |
# number of features because the beginning and ending feature IDs |
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43 |
# are not guaranteed to be 0 and len(layer)-1, respectively. |
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44 |
if index < 0: raise OGRIndexError('Negative indices are not allowed on OGR Layers.') |
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45 |
return self._make_feature(index) |
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46 |
elif isinstance(index, slice): |
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47 |
# A slice was given |
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48 |
start, stop, stride = index.indices(self.num_feat) |
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return [self._make_feature(fid) for fid in xrange(start, stop, stride)] |
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else: |
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51 |
raise TypeError('Integers and slices may only be used when indexing OGR Layers.') |
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52 |
|
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53 |
def __iter__(self): |
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54 |
"Iterates over each Feature in the Layer." |
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# ResetReading() must be called before iteration is to begin. |
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reset_reading(self._ptr) |
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for i in xrange(self.num_feat): |
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yield Feature(get_next_feature(self._ptr), self._ldefn) |
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59 |
|
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def __len__(self): |
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61 |
"The length is the number of features." |
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62 |
return self.num_feat |
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63 |
|
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64 |
def __str__(self): |
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65 |
"The string name of the layer." |
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66 |
return self.name |
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67 |
|
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68 |
def _make_feature(self, feat_id): |
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69 |
""" |
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70 |
Helper routine for __getitem__ that constructs a Feature from the given |
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71 |
Feature ID. If the OGR Layer does not support random-access reading, |
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72 |
then each feature of the layer will be incremented through until the |
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a Feature is found matching the given feature ID. |
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74 |
""" |
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75 |
if self._random_read: |
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76 |
# If the Layer supports random reading, return. |
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77 |
try: |
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78 |
return Feature(get_feature(self._ptr, feat_id), self._ldefn) |
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79 |
except OGRException: |
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80 |
pass |
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81 |
else: |
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82 |
# Random access isn't supported, have to increment through |
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83 |
# each feature until the given feature ID is encountered. |
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84 |
for feat in self: |
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85 |
if feat.fid == feat_id: return feat |
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86 |
# Should have returned a Feature, raise an OGRIndexError. |
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87 |
raise OGRIndexError('Invalid feature id: %s.' % feat_id) |
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88 |
|
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89 |
#### Layer properties #### |
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90 |
@property |
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91 |
def extent(self): |
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92 |
"Returns the extent (an Envelope) of this layer." |
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93 |
env = OGREnvelope() |
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94 |
get_extent(self._ptr, byref(env), 1) |
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95 |
return Envelope(env) |
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96 |
|
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97 |
@property |
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98 |
def name(self): |
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99 |
"Returns the name of this layer in the Data Source." |
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100 |
return get_fd_name(self._ldefn) |
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101 |
|
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102 |
@property |
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103 |
def num_feat(self, force=1): |
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104 |
"Returns the number of features in the Layer." |
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105 |
return get_feature_count(self._ptr, force) |
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106 |
|
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107 |
@property |
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108 |
def num_fields(self): |
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109 |
"Returns the number of fields in the Layer." |
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110 |
return get_field_count(self._ldefn) |
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111 |
|
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112 |
@property |
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|
113 |
def geom_type(self): |
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114 |
"Returns the geometry type (OGRGeomType) of the Layer." |
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115 |
return OGRGeomType(get_fd_geom_type(self._ldefn)) |
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116 |
|
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117 |
@property |
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118 |
def srs(self): |
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119 |
"Returns the Spatial Reference used in this Layer." |
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120 |
try: |
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121 |
ptr = get_layer_srs(self._ptr) |
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122 |
return SpatialReference(clone_srs(ptr)) |
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123 |
except SRSException: |
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124 |
return None |
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125 |
|
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126 |
@property |
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127 |
def fields(self): |
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128 |
""" |
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129 |
Returns a list of string names corresponding to each of the Fields |
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130 |
available in this Layer. |
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131 |
""" |
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132 |
return [get_field_name(get_field_defn(self._ldefn, i)) |
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133 |
for i in xrange(self.num_fields) ] |
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134 |
|
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135 |
@property |
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136 |
def field_types(self): |
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137 |
""" |
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138 |
Returns a list of the types of fields in this Layer. For example, |
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139 |
the list [OFTInteger, OFTReal, OFTString] would be returned for |
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140 |
an OGR layer that had an integer, a floating-point, and string |
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|
141 |
fields. |
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|
142 |
""" |
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143 |
return [FIELD_CLASSES[get_field_type(get_field_defn(self._ldefn, i))] |
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144 |
for i in xrange(self.num_fields)] |
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145 |
|
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|
146 |
@property |
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|
147 |
def field_widths(self): |
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|
148 |
"Returns a list of the maximum field widths for the features." |
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|
149 |
return [get_field_width(get_field_defn(self._ldefn, i)) |
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150 |
for i in xrange(self.num_fields)] |
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|
151 |
|
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152 |
@property |
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|
153 |
def field_precisions(self): |
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154 |
"Returns the field precisions for the features." |
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|
155 |
return [get_field_precision(get_field_defn(self._ldefn, i)) |
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|
156 |
for i in xrange(self.num_fields)] |
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|
157 |
|
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|
158 |
#### Layer Methods #### |
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|
159 |
def get_fields(self, field_name): |
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|
160 |
""" |
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|
161 |
Returns a list containing the given field name for every Feature |
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|
162 |
in the Layer. |
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|
163 |
""" |
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|
164 |
if not field_name in self.fields: |
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|
165 |
raise OGRException('invalid field name: %s' % field_name) |
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|
166 |
return [feat.get(field_name) for feat in self] |
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|
167 |
|
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|
168 |
def get_geoms(self, geos=False): |
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|
169 |
""" |
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|
170 |
Returns a list containing the OGRGeometry for every Feature in |
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|
171 |
the Layer. |
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|
172 |
""" |
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|
173 |
if geos: |
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|
174 |
from django.contrib.gis.geos import GEOSGeometry |
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|
175 |
return [GEOSGeometry(feat.geom.wkb) for feat in self] |
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|
176 |
else: |
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|
177 |
return [feat.geom for feat in self] |
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|
178 |
|
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|
179 |
def test_capability(self, capability): |
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|
180 |
""" |
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|
181 |
Returns a bool indicating whether the this Layer supports the given |
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parents:
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|
182 |
capability (a string). Valid capability strings include: |
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parents:
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|
183 |
'RandomRead', 'SequentialWrite', 'RandomWrite', 'FastSpatialFilter', |
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parents:
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|
184 |
'FastFeatureCount', 'FastGetExtent', 'CreateField', 'Transactions', |
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parents:
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|
185 |
'DeleteFeature', and 'FastSetNextByIndex'. |
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parents:
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|
186 |
""" |
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|
187 |
return bool(test_capability(self._ptr, capability)) |