Source Code for Module gavo.stc.conform

  1  """ 
  2  "Conforming" of STCSpecs, i.e., bringing one to the system and units of the 
  3  other. 
  4   
  5  You can only conform STCSpecs rather than individual components, since  
  6  usually you need the whole information for the transformation (e.g., 
  7  space and time for velocities. 
  8  """ 
  9   
 10  #c Copyright 2008-2019, the GAVO project 
 11  #c 
 12  #c This program is free software, covered by the GNU GPL.  See the 
 13  #c COPYING file in the source distribution. 
 14   
 15   
 16  from gavo.stc import sphermath 
 17  from gavo.stc import times 
 18  from gavo.stc import units 
 19  from gavo.stc import common 
 20   
 21   
 22 -class SphercLoader(object): 
 23          """A hack to delay loading of spherc. 
 24   
 25          We should probably use one of the many lazy import solutions and use 
 26          it for both what we're doing here and in coords.AstWCSLoader. 
 27          """ 
 28 -        def __getattr__(self, *args): 
 29                  from gavo.stc import spherc 
 30                  globals()["spherc"] = spherc 
 31                  return getattr(spherc, *args) 
 32   
 33  spherc = SphercLoader() 
 34   
 35   
 36  _conformedAttributes = [("time", "timeAs"), ("place", "areas"),  
 37          ("freq", "freqAs"), ("redshift", "redshiftAs"), ("velocity", "velocityAs")] 
 38   
 39   
 40 -def _transformAreas(areas, sTrafo, srcFrame, destFrame): 
 41          newAreas = [] 
 42          for a in areas: 
 43                  if a.frame is not srcFrame: 
 44                          raise common.STCError("Cannot transform areas in frame different from" 
 45                                  " from the position frame.") 
 46                  newAreas.append(a.getTransformed(sTrafo, destFrame)) 
 47          return newAreas 
 48   
 49  i = [0] 
 50   
 51 -def iterSpatialChanges(baseSTC, sysSTC, slaComp=False): 
 52          """yields changes to baseSTC to bring places and velocities to the 
 53          system and units of sysSTC. 
 54   
 55          sixTrans is a sphermath.SVConverter instance. 
 56   
 57          If the frame or units are not defined in sysSTC, there are taken from 
 58          baseSTC. 
 59          """ 
 60          if baseSTC.place is None or sysSTC.place is None: 
 61                  return  # nothing to conform in space 
 62          sixTrans = sphermath.SVConverter.fromSTC(baseSTC, slaComp=slaComp) 
 63          destFrame, srcFrame = sysSTC.place.frame, baseSTC.place.frame 
 64   
 65          bPlace, bVel = baseSTC.place, baseSTC.velocity 
 66          trafo = spherc.getTrafoFunction(baseSTC.place.frame.asTriple(), 
 67                  sysSTC.place.frame.asTriple(), sixTrans) 
 68          if bPlace.value: 
 69                  sv = trafo(sixTrans.to6(baseSTC.place.value,  
 70                          getattr(baseSTC.velocity, "value", None)), sixTrans) 
 71                  pos, vel = sixTrans.from6(sv) 
 72          else: 
 73                  pos, vel = None, None 
 74   
 75          # build spatial items to change if necessary 
 76          if bPlace: 
 77                  yield "place", bPlace.change(value=pos, frame=destFrame) 
 78                  if baseSTC.areas: 
 79                          yield "areas", _transformAreas(baseSTC.areas,  
 80                                  sixTrans.getPlaceTransformer(trafo), srcFrame, destFrame) 
 81   
 82          # build velocity items to change if necessary 
 83          if bVel: 
 84                  yield "velocity", bVel.change(value=vel, frame=destFrame) 
 85                  if baseSTC.velocityAs: 
 86                          yield "velocityAs", _transformAreas(baseSTC.velocityAs,  
 87                                  sixTrans.getVelocityTransformer(trafo, bPlace.value), srcFrame,  
 88                                  destFrame) 
 89   
 90   
 91 -def iterTemporalChanges(baseSTC, sysSTC): 
 92          if baseSTC.time is None or sysSTC.time is None: 
 93                  return # nothing to conform in time 
 94          destFrame = sysSTC.time.frame 
 95          transform = times.getTransformFromSTC(baseSTC, sysSTC) 
 96          if transform is None: 
 97                  return # we're already conforming 
 98          if baseSTC.time.value: 
 99                  yield "time", baseSTC.time.change(value=transform( 
100                          baseSTC.time.value), frame=destFrame) 
101          if baseSTC.timeAs: 
102                  yield "timeAs", tuple(ta.getTransformed(transform, destFrame) 
103                          for ta in baseSTC.timeAs) 
104   
105   
106 -def conformUnits(baseSTC, sysSTC): 
107          """returns baseSTC in the units of sysSTC. 
108          """ 
109          changes = [] 
110          for attName, dependentName in _conformedAttributes: 
111                  # TODO: For time, we'd probably have to turn JD, MJD, ISO into 
112                  # each other.  Let's wait for sane STC. 
113                  changes.extend(units.iterUnitAdapted(baseSTC, sysSTC, 
114                          attName, dependentName)) 
115          return baseSTC.change(**dict(changes)) 
116   
117   
118 -def conformSystems(baseSTC, sysSTC, relativistic=False, slaComp=False): 
119          """conforms places and velocities in fromSTC with toSTC including  
120          precession and reference frame fixing. 
121          """ 
122          changes = [("astroSystem", sysSTC.astroSystem)] 
123          changes.extend(iterSpatialChanges(baseSTC, sysSTC, slaComp=slaComp)) 
124          changes.extend(iterTemporalChanges(baseSTC, sysSTC)) 
125          return conformUnits(baseSTC.change(**dict(changes)), sysSTC) 
126   
127   
128 -def conform(baseSTC, sysSTC, **kwargs): 
129          """returns baseSTC in the units and the system of sysSTC. 
130          """ 
131          if baseSTC.astroSystem==sysSTC.astroSystem: 
132                  return conformUnits(baseSTC, sysSTC) 
133          else: 
134                  return conformSystems(baseSTC, sysSTC, **kwargs) 
135   
136   
137 -def getSimple2Converter(srcSTC, destSTC, slaComp=True): 
138          """returns a function that transforms lat and long in srcSTC to lat and 
139          long in destSTC. 
140   
141          srcSTC and destSTC are ASTs.  Of course, all this 
142          only works if srcSTC and destSTC are both SPHER2-flavored. 
143          """ 
144          sixTrans = sphermath.SVConverter.fromSTC(srcSTC, slaComp=slaComp) 
145          trafo = spherc.getTrafoFunction(srcSTC.place.frame.asTriple(), 
146                  destSTC.place.frame.asTriple(), sixTrans) 
147   
148          def convert(ra, dec): 
149                  pos, vel = sixTrans.from6( 
150                          trafo(sixTrans.to6((ra, dec), None), sixTrans)) 
151                  return pos[0], pos[1] 
152           
153          return convert 
154