--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/app/django/contrib/gis/gdal/srs.py Tue Oct 14 16:00:59 2008 +0000
@@ -0,0 +1,360 @@
+"""
+ The Spatial Reference class, represensents OGR Spatial Reference objects.
+
+ Example:
+ >>> from django.contrib.gis.gdal import SpatialReference
+ >>> srs = SpatialReference('WGS84')
+ >>> print srs
+ GEOGCS["WGS 84",
+ DATUM["WGS_1984",
+ SPHEROID["WGS 84",6378137,298.257223563,
+ AUTHORITY["EPSG","7030"]],
+ TOWGS84[0,0,0,0,0,0,0],
+ AUTHORITY["EPSG","6326"]],
+ PRIMEM["Greenwich",0,
+ AUTHORITY["EPSG","8901"]],
+ UNIT["degree",0.01745329251994328,
+ AUTHORITY["EPSG","9122"]],
+ AUTHORITY["EPSG","4326"]]
+ >>> print srs.proj
+ +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
+ >>> print srs.ellipsoid
+ (6378137.0, 6356752.3142451793, 298.25722356300003)
+ >>> print srs.projected, srs.geographic
+ False True
+ >>> srs.import_epsg(32140)
+ >>> print srs.name
+ NAD83 / Texas South Central
+"""
+import re
+from types import UnicodeType, TupleType
+from ctypes import byref, c_char_p, c_int, c_void_p
+
+# Getting the error checking routine and exceptions
+from django.contrib.gis.gdal.error import OGRException, SRSException
+from django.contrib.gis.gdal.prototypes.srs import *
+
+#### Spatial Reference class. ####
+class SpatialReference(object):
+ """
+ A wrapper for the OGRSpatialReference object. According to the GDAL website,
+ the SpatialReference object "provide[s] services to represent coordinate
+ systems (projections and datums) and to transform between them."
+ """
+
+ # Well-Known Geographical Coordinate System Name
+ _well_known = {'WGS84':4326, 'WGS72':4322, 'NAD27':4267, 'NAD83':4269}
+ _epsg_regex = re.compile('^(EPSG:)?(?P<epsg>\d+)$', re.I)
+ _proj_regex = re.compile(r'^\+proj')
+
+ #### Python 'magic' routines ####
+ def __init__(self, srs_input='', srs_type='wkt'):
+ """
+ Creates a GDAL OSR Spatial Reference object from the given input.
+ The input may be string of OGC Well Known Text (WKT), an integer
+ EPSG code, a PROJ.4 string, and/or a projection "well known" shorthand
+ string (one of 'WGS84', 'WGS72', 'NAD27', 'NAD83').
+ """
+ # Intializing pointer and string buffer.
+ self._ptr = None
+ buf = c_char_p('')
+
+ if isinstance(srs_input, basestring):
+ # Encoding to ASCII if unicode passed in.
+ if isinstance(srs_input, UnicodeType):
+ srs_input = srs_input.encode('ascii')
+
+ epsg_m = self._epsg_regex.match(srs_input)
+ proj_m = self._proj_regex.match(srs_input)
+ if epsg_m:
+ # Is this an EPSG well known name?
+ srs_type = 'epsg'
+ srs_input = int(epsg_m.group('epsg'))
+ elif proj_m:
+ # Is the string a PROJ.4 string?
+ srs_type = 'proj'
+ elif srs_input in self._well_known:
+ # Is this a short-hand well known name?
+ srs_type = 'epsg'
+ srs_input = self._well_known[srs_input]
+ elif srs_type == 'proj':
+ pass
+ else:
+ # Setting the buffer with WKT, PROJ.4 string, etc.
+ buf = c_char_p(srs_input)
+ elif isinstance(srs_input, int):
+ # EPSG integer code was input.
+ if srs_type != 'epsg': srs_type = 'epsg'
+ elif isinstance(srs_input, c_void_p):
+ srs_type = 'ogr'
+ else:
+ raise TypeError('Invalid SRS type "%s"' % srs_type)
+
+ if srs_type == 'ogr':
+ # SRS input is OGR pointer
+ srs = srs_input
+ else:
+ # Creating a new pointer, using the string buffer.
+ srs = new_srs(buf)
+
+ # If the pointer is NULL, throw an exception.
+ if not srs:
+ raise SRSException('Could not create spatial reference from: %s' % srs_input)
+ else:
+ self._ptr = srs
+
+ # Post-processing if in PROJ.4 or EPSG formats.
+ if srs_type == 'proj': self.import_proj(srs_input)
+ elif srs_type == 'epsg': self.import_epsg(srs_input)
+
+ def __del__(self):
+ "Destroys this spatial reference."
+ if self._ptr: release_srs(self._ptr)
+
+ def __getitem__(self, target):
+ """
+ Returns the value of the given string attribute node, None if the node
+ doesn't exist. Can also take a tuple as a parameter, (target, child),
+ where child is the index of the attribute in the WKT. For example:
+
+ >>> wkt = 'GEOGCS["WGS 84", DATUM["WGS_1984, ... AUTHORITY["EPSG","4326"]]')
+ >>> srs = SpatialReference(wkt) # could also use 'WGS84', or 4326
+ >>> print srs['GEOGCS']
+ WGS 84
+ >>> print srs['DATUM']
+ WGS_1984
+ >>> print srs['AUTHORITY']
+ EPSG
+ >>> print srs['AUTHORITY', 1] # The authority value
+ 4326
+ >>> print srs['TOWGS84', 4] # the fourth value in this wkt
+ 0
+ >>> print srs['UNIT|AUTHORITY'] # For the units authority, have to use the pipe symbole.
+ EPSG
+ >>> print srs['UNIT|AUTHORITY', 1] # The authority value for the untis
+ 9122
+ """
+ if isinstance(target, TupleType):
+ return self.attr_value(*target)
+ else:
+ return self.attr_value(target)
+
+ def __str__(self):
+ "The string representation uses 'pretty' WKT."
+ return self.pretty_wkt
+
+ #### SpatialReference Methods ####
+ def attr_value(self, target, index=0):
+ """
+ The attribute value for the given target node (e.g. 'PROJCS'). The index
+ keyword specifies an index of the child node to return.
+ """
+ if not isinstance(target, str) or not isinstance(index, int):
+ raise TypeError
+ return get_attr_value(self._ptr, target, index)
+
+ def auth_name(self, target):
+ "Returns the authority name for the given string target node."
+ return get_auth_name(self._ptr, target)
+
+ def auth_code(self, target):
+ "Returns the authority code for the given string target node."
+ return get_auth_code(self._ptr, target)
+
+ def clone(self):
+ "Returns a clone of this SpatialReference object."
+ return SpatialReference(clone_srs(self._ptr))
+
+ def from_esri(self):
+ "Morphs this SpatialReference from ESRI's format to EPSG."
+ morph_from_esri(self._ptr)
+
+ def identify_epsg(self):
+ """
+ This method inspects the WKT of this SpatialReference, and will
+ add EPSG authority nodes where an EPSG identifier is applicable.
+ """
+ identify_epsg(self._ptr)
+
+ def to_esri(self):
+ "Morphs this SpatialReference to ESRI's format."
+ morph_to_esri(self._ptr)
+
+ def validate(self):
+ "Checks to see if the given spatial reference is valid."
+ srs_validate(self._ptr)
+
+ #### Name & SRID properties ####
+ @property
+ def name(self):
+ "Returns the name of this Spatial Reference."
+ if self.projected: return self.attr_value('PROJCS')
+ elif self.geographic: return self.attr_value('GEOGCS')
+ elif self.local: return self.attr_value('LOCAL_CS')
+ else: return None
+
+ @property
+ def srid(self):
+ "Returns the SRID of top-level authority, or None if undefined."
+ try:
+ return int(self.attr_value('AUTHORITY', 1))
+ except (TypeError, ValueError):
+ return None
+
+ #### Unit Properties ####
+ @property
+ def linear_name(self):
+ "Returns the name of the linear units."
+ units, name = linear_units(self._ptr, byref(c_char_p()))
+ return name
+
+ @property
+ def linear_units(self):
+ "Returns the value of the linear units."
+ units, name = linear_units(self._ptr, byref(c_char_p()))
+ return units
+
+ @property
+ def angular_name(self):
+ "Returns the name of the angular units."
+ units, name = angular_units(self._ptr, byref(c_char_p()))
+ return name
+
+ @property
+ def angular_units(self):
+ "Returns the value of the angular units."
+ units, name = angular_units(self._ptr, byref(c_char_p()))
+ return units
+
+ @property
+ def units(self):
+ """
+ Returns a 2-tuple of the units value and the units name,
+ and will automatically determines whether to return the linear
+ or angular units.
+ """
+ if self.projected or self.local:
+ return linear_units(self._ptr, byref(c_char_p()))
+ elif self.geographic:
+ return angular_units(self._ptr, byref(c_char_p()))
+ else:
+ return (None, None)
+
+ #### Spheroid/Ellipsoid Properties ####
+ @property
+ def ellipsoid(self):
+ """
+ Returns a tuple of the ellipsoid parameters:
+ (semimajor axis, semiminor axis, and inverse flattening)
+ """
+ return (self.semi_major, self.semi_minor, self.inverse_flattening)
+
+ @property
+ def semi_major(self):
+ "Returns the Semi Major Axis for this Spatial Reference."
+ return semi_major(self._ptr, byref(c_int()))
+
+ @property
+ def semi_minor(self):
+ "Returns the Semi Minor Axis for this Spatial Reference."
+ return semi_minor(self._ptr, byref(c_int()))
+
+ @property
+ def inverse_flattening(self):
+ "Returns the Inverse Flattening for this Spatial Reference."
+ return invflattening(self._ptr, byref(c_int()))
+
+ #### Boolean Properties ####
+ @property
+ def geographic(self):
+ """
+ Returns True if this SpatialReference is geographic
+ (root node is GEOGCS).
+ """
+ return bool(isgeographic(self._ptr))
+
+ @property
+ def local(self):
+ "Returns True if this SpatialReference is local (root node is LOCAL_CS)."
+ return bool(islocal(self._ptr))
+
+ @property
+ def projected(self):
+ """
+ Returns True if this SpatialReference is a projected coordinate system
+ (root node is PROJCS).
+ """
+ return bool(isprojected(self._ptr))
+
+ #### Import Routines #####
+ def import_wkt(self, wkt):
+ "Imports the Spatial Reference from OGC WKT (string)"
+ from_wkt(self._ptr, byref(c_char_p(wkt)))
+
+ def import_proj(self, proj):
+ "Imports the Spatial Reference from a PROJ.4 string."
+ from_proj(self._ptr, proj)
+
+ def import_epsg(self, epsg):
+ "Imports the Spatial Reference from the EPSG code (an integer)."
+ from_epsg(self._ptr, epsg)
+
+ def import_xml(self, xml):
+ "Imports the Spatial Reference from an XML string."
+ from_xml(self._ptr, xml)
+
+ #### Export Properties ####
+ @property
+ def wkt(self):
+ "Returns the WKT representation of this Spatial Reference."
+ return to_wkt(self._ptr, byref(c_char_p()))
+
+ @property
+ def pretty_wkt(self, simplify=0):
+ "Returns the 'pretty' representation of the WKT."
+ return to_pretty_wkt(self._ptr, byref(c_char_p()), simplify)
+
+ @property
+ def proj(self):
+ "Returns the PROJ.4 representation for this Spatial Reference."
+ return to_proj(self._ptr, byref(c_char_p()))
+
+ @property
+ def proj4(self):
+ "Alias for proj()."
+ return self.proj
+
+ @property
+ def xml(self, dialect=''):
+ "Returns the XML representation of this Spatial Reference."
+ # FIXME: This leaks memory, have to figure out why.
+ return to_xml(self._ptr, byref(c_char_p()), dialect)
+
+ def to_esri(self):
+ "Morphs this SpatialReference to ESRI's format."
+ morph_to_esri(self._ptr)
+
+ def from_esri(self):
+ "Morphs this SpatialReference from ESRI's format to EPSG."
+ morph_from_esri(self._ptr)
+
+class CoordTransform(object):
+ "The coordinate system transformation object."
+
+ def __init__(self, source, target):
+ "Initializes on a source and target SpatialReference objects."
+ self._ptr = None # Initially NULL
+ if not isinstance(source, SpatialReference) or not isinstance(target, SpatialReference):
+ raise SRSException('source and target must be of type SpatialReference')
+ self._ptr = new_ct(source._ptr, target._ptr)
+ if not self._ptr:
+ raise SRSException('could not intialize CoordTransform object')
+ self._srs1_name = source.name
+ self._srs2_name = target.name
+
+ def __del__(self):
+ "Deletes this Coordinate Transformation object."
+ if self._ptr: destroy_ct(self._ptr)
+
+ def __str__(self):
+ return 'Transform from "%s" to "%s"' % (self._srs1_name, self._srs2_name)