1 """

     2  This module houses ctypes interfaces for GDAL objects.  The following GDAL

     3  objects are supported:

     4 

     5  CoordTransform: Used for coordinate transformations from one spatial

     6   reference system to another.

     7 

     8  Driver: Wraps an OGR data source driver.

     9   

    10  DataSource: Wrapper for the OGR data source object, supports

    11   OGR-supported data sources.

    12 

    13  Envelope: A ctypes structure for bounding boxes (GDAL library

    14   not required).

    15 

    16  OGRGeometry: Layer for accessing OGR Geometry objects.

    17 

    18  OGRGeomType: A class for representing the different OGR Geometry

    19   types (GDAL library not required).

    20 

    21  SpatialReference: Represents OSR Spatial Reference objects.

    22 

    23  The GDAL library will be imported from the system path using the default  

    24  library name for the current OS. The default library path may be overridden

    25  by setting `GDAL_LIBRARY_PATH` in your settings with the path to the GDAL C 

    26  library on your system.  

    27 

    28  GDAL links to a large number of external libraries that consume RAM when 

    29  loaded.  Thus, it may desirable to disable GDAL on systems with limited

    30  RAM resources -- this may be accomplished by setting `GDAL_LIBRARY_PATH`

    31  to a non-existant file location (e.g., `GDAL_LIBRARY_PATH='/null/path'`; 

    32  setting to None/False/'' will not work as a string must be given).

    33 """

    34 import sys

    35 

    36 # Attempting to import objects that depend on the GDAL library.  The

    37 # HAS_GDAL flag will be set to True if the library is present on

    38 # the system.

    39 try:

    40     from django.contrib.gis.gdal.driver import Driver

    41     from django.contrib.gis.gdal.datasource import DataSource

    42     from django.contrib.gis.gdal.libgdal import gdal_version, gdal_full_version, gdal_release_date

    43     from django.contrib.gis.gdal.srs import SpatialReference, CoordTransform

    44     from django.contrib.gis.gdal.geometries import OGRGeometry, GEOJSON

    45     HAS_GDAL = True

    46 except:

    47     HAS_GDAL, GEOJSON = False, False

    48 

    49 # The envelope, error, and geomtype modules do not actually require the

    50 # GDAL library, but still nead at least Python 2.4 and ctypes.

    51 PYTHON23 = sys.version_info[0] == 2 and sys.version_info[1] == 3

    52 if not PYTHON23:

    53     try:

    54         from django.contrib.gis.gdal.envelope import Envelope

    55         from django.contrib.gis.gdal.error import check_err, OGRException, OGRIndexError, SRSException

    56         from django.contrib.gis.gdal.geomtype import OGRGeomType

    57     except ImportError:

    58         # No ctypes, but don't raise an exception.

    59         pass