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PyCRS/pycrs/parser.py
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"""
The main module containing functions for parsing text strings into crs objects.
"""
# possible use module: https://github.com/rockdoc/grabbag/wiki/CRS-WKT-Parser
# also note some paramter descriptions: http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html
# and see gdal source code: http://gis.stackexchange.com/questions/129764/how-are-esri-wkt-projections-different-from-ogc-wkt-projections
# especially: http://fossies.org/windows/misc/saga_2.1.4_x64.zip/saga_2.1.4_x64/saga_prj.dic
# also: http://saga.sourcearchive.com/documentation/2.0.7plus-pdfsg-2/crs__base_8cpp_source.html
from .elements import datums
from .elements import ellipsoids
from .elements import parameters
from .elements import containers
from .elements import units
from .elements import projections
from . import utils
def from_epsg_code(code):
"""
Load crs object from epsg code, via spatialreference.org.
Parses based on the proj4 representation.
Arguments:
- *code*: The EPSG code as an integer.
Returns:
- CRS object.
"""
# must go online (or look up local table) to get crs details
code = str(code)
proj4 = utils.crscode_to_string("epsg", code, "proj4")
crs = from_proj4(proj4)
return crs
def from_esri_code(code):
"""
Load crs object from esri code, via spatialreference.org.
Parses based on the proj4 representation.
Arguments:
- *code*: The ESRI code as an integer.
Returns:
- CRS object.
"""
# must go online (or look up local table) to get crs details
code = str(code)
proj4 = utils.crscode_to_string("esri", code, "proj4")
crs = from_proj4(proj4)
return crs
def from_sr_code(code):
"""
Load crs object from sr-org code, via spatialreference.org.
Parses based on the proj4 representation.
Arguments:
- *code*: The SR-ORG code as an integer.
Returns:
- CRS object.
"""
# must go online (or look up local table) to get crs details
code = str(code)
proj4 = utils.crscode_to_string("sr-org", code, "proj4")
crs = from_proj4(proj4)
return crs
def from_ogc_wkt(string, strict=False):
"""
Parse crs as ogc wkt formatted string and return the resulting crs object.
Arguments:
- *string*: The OGC WKT representation as a string.
- *strict* (optional): When True, the parser is strict about names having to match
exactly with upper and lowercases. Default is not strict (False).
Returns:
- CRS object.
"""
# parse arguments into components
# use args to create crs
return _from_wkt(string, "ogc", strict)
def from_esri_wkt(string, strict=False):
"""
Parse crs as esri wkt formatted string and return the resulting crs object.
Arguments:
- *string*: The ESRI WKT representation as a string.
- *strict* (optional): When True, the parser is strict about names having to match
exactly with upper and lowercases. Default is not strict (False).
Returns:
- CRS object.
"""
# parse arguments into components
# use args to create crs
return _from_wkt(string, "esri", strict)
def from_unknown_wkt(string, strict=False):
"""
Given an unknown wkt string, detect if uses ogc or esri flavor, and parse the crs accordingly.
Arguments:
- *string*: The unknown WKT representation as a string.
- *strict* (optional): When True, the parser is strict about names having to match
exactly with upper and lowercases. Default is not strict (False).
Returns:
- CRS object.
"""
# parse arguments into components
# use args to create crs
return _from_wkt(string, None, strict)
def _from_wkt(string, wkttype, strict=False):
"""
Internal method for parsing wkt, with minor differences depending on ogc or esri style.
Arguments:
- *string*: The OGC or ESRI WKT representation as a string.
- *wkttype* (optional): How to parse the WKT string, as either 'ogc', 'esri', or None. If None, tries to autodetect the wkt type before parsing (default).
- *strict* (optional): When True, the parser is strict about names having to match
exactly with upper and lowercases. Default is not strict (False).
Returns:
- CRS object.
"""
# TODO
# - Make function for finding next elemt by name, instead of knowing its arg index position
# - Maybe verify elem arg name
# make sure valid wkttype
if wkttype: wkttype = wkttype.lower()
assert wkttype in ("ogc","esri",None)
# remove newlines and multi spaces
string = " ".join(string.split())
# parse arguments into components
def _consume_bracket(chars, char):
"char must be the opening bracket"
consumed = ""
depth = 1
while char and depth > 0:
consumed += char
char = next(chars, None)
# update depth level
if char == "[":
depth += 1
elif char == "]":
depth -= 1
consumed += char # consume the last closing char too
return consumed
def _consume_quote(chars, char, quotechar):
"char and quotechar must be the opening quote char"
consumed = ""
# consume the first opening char
consumed += char
char = next(chars, None)
# consume inside
while char and char != quotechar:
consumed += char
char = next(chars, None)
# consume the last closing char too
consumed += char
return consumed
def _next_elem(chars, char):
"char must be the first char of the text that precedes brackets"
header = ""
# skip until next header
while not char.isalpha():
char = next(chars, None)
# first consume the element text header
while char.isalpha():
header += char
char = next(chars, None)
# skip until next brackets (in case of spaces)
while char != "[":
char = next(chars, None)
# then consume the element bracket contents
if char == "[":
content = _consume_bracket(chars, char)
char = next(chars, None)
# split content into args list
content = content[1:-1] # remove enclosing brackets
content = _split_except(content)
# recursively load all subelems
for i,item in enumerate(content):
if isinstance(item, str) and "[" in item:
chars = (char for char in item)
char = next(chars)
item = _next_elem(chars, char)
content[i] = item
return header, content
def _clean_value(string):
string = string.strip()
try: string = float(string)
except: pass
return string
def _split_except(string):
"split the string on every comma, except not while inside quotes or square brackets"
chars = (char for char in string)
char = next(chars)
items = []
consumed = ""
while char:
# dont split on quotes, just consume it
if char in ("'", '"'):
consumed += _consume_quote(chars, char, char)
# dont split inside brackets, just consume it
elif char == "[":
consumed += _consume_bracket(chars, char)
# new splitchar found, add what has been consumed so far as an item, reset, and start consuming until next splitchar
elif char == ",":
consumed = _clean_value(consumed)
items.append(consumed)
consumed = ""
# consume normal char
elif char:
consumed += char
# next
char = next(chars, None)
# append last item too
consumed = _clean_value(consumed)
items.append(consumed)
return items
# load into nested tuples and arglists
crstuples = []
chars = (char for char in string)
char = next(chars)
while char:
header,content = _next_elem(chars, char)
crstuples.append((header, content))
char = next(chars, None)
# autodetect wkttype if not specified
if not wkttype:
topheader,topcontent = crstuples[0]
if topheader == "PROJCS":
geogcsheader,geogcscontent = topcontent[1]
elif topheader == "GEOGCS":
geogcsheader,geogcscontent = topheader,topcontent
# datum elem should be second under geogcs
datumheader, datumcontent = geogcscontent[1]
datumname = datumcontent[0].upper().strip('"')
# esri wkt datums all use "D_" before the datum name
if datumname.startswith("D_"):
wkttype = "esri"
else:
wkttype = "ogc"
# parse into actual crs objects
def _parse_top(header, content):
"procedure for parsing the toplevel crs element and all its children"
if header.upper() == "PROJCS":
# find name
name = content[0].strip('"')
# find geogcs elem (by running parse again)
subheader, subcontent = content[1]
geogcs = _parse_top(subheader, subcontent)
# find projection elem
subheader, subcontent = content[2]
projname = subcontent[0].strip('"')
projclass = projections.find(projname, "%s_wkt" % wkttype, strict)
if projclass:
projdef = projclass()
proj = containers.Projection(projdef)
else:
raise Exception("The specified projection name could not be found")
# find params
params = []
for part in content:
if isinstance(part, tuple):
subheader,subcontent = part
if subheader == "PARAMETER":
name, value = subcontent[0].strip('"'), subcontent[1]
itemclass = parameters.find(name, "%s_wkt" % wkttype, strict)
if itemclass:
item = itemclass(value)
params.append(item)
# find unit
for part in content:
if isinstance(part, tuple):
subheader,subcontent = part
if subheader == "UNIT":
break
unitname,value = subcontent[0].strip('"'), subcontent[1]
unitclass = units.find(unitname, "%s_wkt" % wkttype, strict)
if unitclass:
unit = unitclass()
unittype = parameters.UnitType(unit)
else:
unit = units.Unknown()
unittype = parameters.UnitType(unit)
metmult = parameters.MeterMultiplier(value)
linunit = parameters.Unit(unittype, metmult)
# find twin axis maybe
## if len(content) >= 6:
## twinax = (parameters.Axis(
## else:
## twinax = None
# put it all together
projcs = containers.ProjCS("Unknown", geogcs, proj, params, linunit) #, twinax)
return projcs
elif header.upper() == "GEOGCS":
# name
name = content[0].strip('"')
# datum
subheader, subcontent = content[1]
## datum name
datumname = subcontent[0].strip('"')
datumclass = datums.find(datumname, "%s_wkt" % wkttype, strict)
if datumclass:
datumdef = datumclass()
else:
datumdef = datums.Unknown()
## datum ellipsoid
subsubheader, subsubcontent = subcontent[1]
ellipsname = subsubcontent[0].strip('"')
ellipsclass = ellipsoids.find(ellipsname, "%s_wkt" % wkttype, strict)
if ellipsclass:
ellipsdef = ellipsclass()
else:
ellipsdef = ellipsoids.Unknown()
ellipsoid = containers.Ellipsoid(ellipsdef, subsubcontent[1], subsubcontent[2])
## datum shift
if wkttype == "ogc":
for subsubheader,subsubcontent in subcontent[1:]:
if subsubheader == "TOWGS84":
datumshift = parameters.DatumShift(subsubcontent)
break
else:
datumshift = None
elif wkttype == "esri":
# not used in esri wkt
datumshift = None
## put it all togehter
datum = containers.Datum(datumdef, ellipsoid, datumshift)
# prime mer
subheader, subcontent = content[2]
prime_mer = parameters.PrimeMeridian(subcontent[1])
# angunit
subheader, subcontent = content[3]
unitname,value = subcontent[0].strip('"'), subcontent[1]
unitclass = units.find(unitname, "%s_wkt" % wkttype, strict)
if unitclass:
unit = unitclass()
unittype = parameters.UnitType(unit)
else:
unit = units.Unknown()
unittype = parameters.UnitType(unit)
metmult = parameters.MeterMultiplier(value)
angunit = parameters.AngularUnit(unittype, metmult)
# twin axis
# ...
# put it all together
geogcs = containers.GeogCS(name, datum, prime_mer, angunit, twin_ax=None)
return geogcs
# toplevel collection
header, content = crstuples[0]
toplevel = _parse_top(header, content)
crs = containers.CRS(toplevel)
# use args to create crs
return crs
def from_proj4(string, strict=False):
"""
Parse crs as proj4 formatted string and return the resulting crs object.
Arguments:
- *string*: The proj4 representation as a string.
- *strict* (optional): When True, the parser is strict about names having to match
exactly with upper and lowercases. Default is not strict (False).
Returns:
- CRS object.
"""
# parse arguments into components
# use args to create crs
# TODO: SLIGTHLY MESSY STILL, CLEANUP..
params = []
partdict = dict([part.split("=") for part in string.split()
if len(part.split("=")) == 2 ])
# INIT CODES
# eg, +init=EPSG:1234
if "+init" in partdict:
# first, get the default proj4 string of the +init code
codetype, code = partdict["+init"].split(":")
if codetype == "EPSG":
initproj4 = utils.crscode_to_string("epsg", code, "proj4")
elif codetype == "ESRI":
initproj4 = utils.crscode_to_string("esri", code, "proj4")
# make the default into param dict
initpartdict = dict([part.split("=") for part in initproj4.split()
if len(part.split("=")) == 2 ])
# override the default with any custom params specified along with the +init code
initpartdict.update(partdict)
# rerun from_proj4() again on the derived proj4 params as if it was not made with the +init code
del initpartdict["+init"]
string = " ".join("%s=%s" % (key,val) for key,val in initpartdict.items())
return from_proj4(string)
# DATUM
# datum param is required
if "+datum" in partdict:
# get predefined datum def
datumname = partdict["+datum"]
datumclass = datums.find(datumname, "proj4", strict)
if datumclass:
datumdef = datumclass()
else:
datumdef = datums.Unknown()
else:
datumdef = datums.Unknown()
# ELLIPS
# ellipse param is required
if "+ellps" in partdict:
# get predefined ellips def
ellipsname = partdict["+ellps"]
ellipsclass = ellipsoids.find(ellipsname, "proj4", strict)
if ellipsclass:
ellipsdef = ellipsclass
elif "+a" in partdict and "+f" in partdict:
ellipsdef = ellipsoids.Unknown()
else:
raise Exception("The specified ellipsoid name could not be found, and there was no manual specification of the semimajor axis and inverse flattening to use as a substitute.")
elif "+a" in partdict and "+f" in partdict:
# alternatively, it is okay with a missing ellipsoid if +a and +f are specified
# TODO: +f seems to never be specified when +ellps is missing, only +a and +b, look into...
ellipsdef = ellipsoids.Unknown()
else:
raise Exception("Could not find the required +ellps element, nor a manual specification of the +a or +f elements.")
# TO WGS 84 COEFFS
if "+towgs84" in partdict:
coeffs = partdict["+towgs84"].split(",")
datumshift = parameters.DatumShift(coeffs)
# TODO: if no datum, use ellips + towgs84 params to create the correct datum
# ...??
# COMBINE DATUM AND ELLIPS
## create datum and ellips param objs
ellips = containers.Ellipsoid(ellipsdef,
semimaj_ax=partdict.get("+a"),
inv_flat=partdict.get("+f"))
if "+datum" in partdict:
datum = containers.Datum(datumdef, ellips)
elif "+towgs84" in partdict:
datum = containers.Datum(datumdef, ellips, datumshift)
else:
datum = containers.Datum(datumdef, ellips)
# PRIME MERIDIAN
# set default
prime_mer = parameters.PrimeMeridian(0)
# overwrite with user input
if "+pm" in partdict:
# for now only support longitude, later add name support from below:
## greenwich 0dE
## lisbon 9d07'54.862"W
## paris 2d20'14.025"E
## bogota 74d04'51.3"E
## madrid 3d41'16.48"W
## rome 12d27'8.4"E
## bern 7d26'22.5"E
## jakarta 106d48'27.79"E
## ferro 17d40'W
## brussels 4d22'4.71"E
## stockholm 18d3'29.8"E
## athens 23d42'58.815"E
## oslo 10d43'22.5"E
prime_mer = parameters.PrimeMeridian(partdict["+pm"])
# ANGULAR UNIT
## proj4 cannot set angular unit, so just set to default
metmulti = parameters.MeterMultiplier(0.017453292519943295)
unittype = parameters.UnitType(units.Degree())
angunit = parameters.AngularUnit(unittype, metmulti)
# GEOGCS (note, currently does not load axes)
geogcs = containers.GeogCS("Unknown", datum, prime_mer, angunit) #, twin_ax)
# PROJECTION
if "+proj" in partdict:
# get predefined proj def
projname = partdict["+proj"]
projclass = projections.find(projname, "proj4", strict)
if projclass:
projdef = projclass()
elif projname == "longlat":
# proj4 special case, longlat as projection name means unprojected geogcs
projdef = None
else:
raise Exception("The specified projection name could not be found")
else:
raise Exception("Could not find required +proj element")
if projdef:
# create proj param obj
proj = containers.Projection(projdef)
# Because proj4 has no element hierarchy, using automatic element find() would
# ...would not be very effective, as that would need a try-fail approach for each
# ...element type (parameter, projection, datum, ellipsoid, unit).
# ...Instead load each element individually.
# CENTRAL MERIDIAN
if "+lon_0" in partdict:
val = partdict["+lon_0"]
obj = parameters.CentralMeridian(val)
params.append(obj)
# FALSE EASTING
if "+x_0" in partdict:
val = partdict["+x_0"]
obj = parameters.FalseEasting(val)
params.append(obj)
# FALSE NORTHING
if "+y_0" in partdict:
val = partdict["+y_0"]
obj = parameters.FalseNorthing(val)
params.append(obj)
# SCALING FACTOR
if "+k_0" in partdict or "+k" in partdict:
if "+k_0" in partdict: val = partdict["+k_0"]
elif "+k" in partdict: val = partdict["+k"]
obj = parameters.ScalingFactor(val)
params.append(obj)
# LATITUDE ORIGIN
if "+lat_0" in partdict:
val = partdict["+lat_0"]
obj = parameters.LatitudeOrigin(val)
params.append(obj)
# LATITUDE TRUE SCALE
if "+lat_ts" in partdict:
val = partdict["+lat_ts"]
obj = parameters.LatitudeTrueScale(val)
params.append(obj)
# LONGITUDE CENTER
if "+lonc" in partdict:
val = partdict["+lonc"]
obj = parameters.LongitudeCenter(val)
params.append(obj)
# AZIMUTH
if "+alpha" in partdict:
val = partdict["+alpha"]
obj = parameters.Azimuth(val)
params.append(obj)
# STD PARALLEL 1
if "+lat1" in partdict:
val = partdict["+lat1"]
obj = parameters.LatitudeFirstStndParallel(val)
params.append(obj)
# STD PARALLEL 2
if "+lat2" in partdict:
val = partdict["+lat2"]
obj = parameters.LatitudeSecondStndParallel(val)
params.append(obj)
# SATELLITE HEIGHT
if "+h" in partdict:
val = partdict["+h"]
obj = parameters.SatelliteHeight(val)
params.append(obj)
# TILT ANGLE
if "+tilt" in partdict:
val = partdict["+tilt"]
obj = parameters.TiltAngle(val)
params.append(obj)
# UNIT
## set default
metmulti = parameters.MeterMultiplier(1.0)
unittype = parameters.UnitType(units.Meter())
## override with user input
if "+to_meter" in partdict:
metmulti = parameters.MeterMultiplier(partdict["+to_meter"])
if "+units" in partdict:
unitname = partdict["+units"]
unitclass = units.find(unitname, "proj4", strict)
if unitclass:
unit = unitclass()
unittype = parameters.UnitType(unit)
else:
raise Exception("The specified unit name could not be found")
## create unitobj
unit = parameters.Unit(unittype, metmulti)
# PROJCS
projcs = containers.ProjCS("Unknown", geogcs, proj, params, unit)
# CRS
crs = containers.CRS(projcs)
else:
# means projdef was None, ie unprojected longlat geogcs
crs = containers.CRS(geogcs)
# FINISHED
return crs
##def from_ogc_urn(string, strict=False):
## # hmmm, seems like ogc urn could be anything incl online link, epsg, etc...
## # if necessary, must go online (or lookup local table) to get details
## # maybe test which of these and run their function?
## # examples urn:ogc:def:crs:OGC:1.3:CRS1
## # or with EPSG instead of OGC
##
## # If OGC, 1.3 is pdf version, and after that is a name from list below
## # as found in pdf: "Definition identifier URNs in OGC namespace"
## # OGC crs definitions
## # URN | CRS name | Definition reference
## # urn:ogc:def:crs:OGC:1.3:CRS1 Map CS B.2 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:CRS84 WGS 84 longitude-latitude B.3 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:CRS83 NAD83 longitude-latitude B.4 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:CRS27 NAD27 longitude-latitude B.5 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:CRS88 NAVD 88 B.6 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:AUTO42001:99:8888 Auto universal transverse mercator B.7 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:AUTO42002:99:8888 Auto transverse mercator B.8 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:AUTO42003:99:8888 Auto orthographic B.9 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:AUTO42004:99:8888 Auto equirectangular B.10 in OGC 06-042
## # urn:ogc:def:crs:OGC:1.3:AUTO42005:99 Auto Mollweide B.11 in OGC 06-042
##
## pass
def from_unknown_text(text, strict=False):
"""
Detect crs string format and parse into crs object with appropriate function.
Arguments:
- *string*: The crs text representation of unknown type.
- *strict* (optional): When True, the parser is strict about names having to match
exactly with upper and lowercases. Default is not strict (False).
Returns:
- CRS object.
"""
if string.startswith("+"):
from_proj4(string, strict)
elif string.startswith(("PROJCS[","GEOGCS[")):
from_unknown_wkt(string, strict)
#elif string.startswith("urn:"):
# from_ogc_urn(string, strict)
elif string.startswith("EPSG:"):
from_epsg_code(string.split(":")[1])
elif string.startswith("ESRI:"):
from_esri_code(string.split(":")[1])
elif string.startswith("SR-ORG:"):
from_sr_code(string.split(":")[1])
else: raise Exception("Could not detect which type of crs")
##def from_geotiff_parameters(**params):
## pass
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