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Diffstat (limited to 'webapp/django/contrib/gis/gdal/srs.py')
-rw-r--r-- | webapp/django/contrib/gis/gdal/srs.py | 360 |
1 files changed, 360 insertions, 0 deletions
diff --git a/webapp/django/contrib/gis/gdal/srs.py b/webapp/django/contrib/gis/gdal/srs.py new file mode 100644 index 0000000000..d70e71ebc7 --- /dev/null +++ b/webapp/django/contrib/gis/gdal/srs.py @@ -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) |