/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/resource.py
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revision 1791 by jan, Wed Oct 8 14:47:53 2003 UTC revision 1964 by bh, Wed Nov 19 19:48:47 2003 UTC
# Line 14  __version__ = "$Revision$" Line 14  __version__ = "$Revision$"
14    
15  import os  import os
16  import os.path  import os.path
17    import weakref
18    import traceback
19    
20  import Thuban  import Thuban
21  from Thuban import _  from Thuban import _
# Line 31  projdir = \ Line 33  projdir = \
33    
34  PROJ_EXT = ".proj"  PROJ_EXT = ".proj"
35    
36  has_gdal_support = lambda: False  # Determine the status of GDAL support. If GDAL is supported
37  try:  # gdal_support_status will be set to the empty string, otherwise to a
38      # first try to see if our extension module is there. if it  # string with information why it isn't supported
39      # wasn't even compiled, we obviously don't have gdal support.  #
40      import gdalwarp  # GDAL is supported if we can import both the thuban specific gdalwarp
41    # module and the GDAL python bindings.
42      # now try to import the python extension. if this doesn't  for _module in ("gdalwarp", "gdal"):
43      # exist then we can't do anything.      try:
44      import gdal          __import__(_module)
45        except ImportError, val:
46      """Return True if the gdal library is available."""          gdal_support_status = (_("No GDAL support because module '%s'"
47      has_gdal_support = lambda: True                                   " cannot be imported. Python exception: '%s'")
48  except ImportError:                                 % (_module, str(val)))
49      pass          break
50    else:
51        gdal_support_status = ""
52    
53    def has_gdal_support():
54        return gdal_support_status == ""
55    
56    
57    projfile_cache = weakref.WeakValueDictionary()
58    
59    def clear_proj_file_cache():
60        """Clear the cache of ProjFile objects maintained by read_proj_file.
61    
62        This function is probably only useful for the test suite.
63        """
64        projfile_cache.clear()
65    
66  def read_proj_file(filename):  def read_proj_file(filename):
67      """Read a .proj file and return a ProjFile object and warnings      """Read a .proj file and return a ProjFile object and warnings
68    
69      The return value is a tuple with the ProjFile object and a list of      The return value is a tuple with the ProjFile object and a list of
70      strings with warnings messages that might have been generated by the      strings with warnings messages that might have been generated by the
71      proj ifle parser.      proj file parser.
72    
73        The objects returned cached so that reading the same file
74        (identified by its absolute name) several times yields the same
75        ProjFile object. The cache uses weak references so the objects will
76        be removed from the cache once the last reference an object in the
77        cache is removed.
78    
79      Raises IOError if the file cannot be opened, OSError if the file      Raises IOError if the file cannot be opened, OSError if the file
80      cannot be read and SAXParseException if the file is not valid XML.      cannot be read and SAXParseException if the file is not valid XML.
81      """      """
82      handler = ProjFileReader()      filename = os.path.abspath(filename)
83      handler.read(filename)      if filename in projfile_cache:
84      return handler.GetProjFile(), handler.GetWarnings()          return projfile_cache[filename], []
85        else:
86            handler = ProjFileReader()
87            handler.read(filename)
88            proj_file = handler.GetProjFile()
89            projfile_cache[filename] = proj_file
90            return proj_file, handler.GetWarnings()
91    
92  def write_proj_file(pf):  def write_proj_file(pf):
93      """Write a single .proj file      """Write a single .proj file
# Line 69  def write_proj_file(pf): Line 98  def write_proj_file(pf):
98      saver = ProjFileSaver(pf)      saver = ProjFileSaver(pf)
99      saver.write(pf.GetFilename())      saver.write(pf.GetFilename())
100    
101    #
102  def get_system_proj_file():  # Constants for the get_system_proj_file function
103      """Return the standard projections and a list with warnings  #
104    
105      The projections read from the default thuban projection file  # The default projection file with a few predefined projections
106      (usually in Resources/Projections/defaults.proj). The return value  DEFAULT_PROJ_FILE = "defaults.proj"
107      is a tuple with the projections in a ProjFile object and a list of  
108      strings with warning messages. The warnings list is usually empty  # The epsg projections.
109      but may contain messages about ignored errors.  EPSG_PROJ_FILE = "epsg.proj"
110    
111    # Deprecated EPSG projections.
112    EPSG_DEPRECATED_PROJ_FILE = "epsg-deprecated.proj"
113    
114    def get_system_proj_file(filename):
115        """Return the projections from the indicated file and a list with warnings
116    
117        The filename argument should be the name of a file in the directory
118        with Thuban's default projection files (Resources/Projections/). If
119        possible callers should not use hardwired string literal for the
120        name to avoid unnecessary duplication. Instead they should use one
121        of the predefined constants, currently DEFAULT_PROJ_FILE,
122        EPSG_PROJ_FILE or EPSG_DEPRECATED_PROJ_FILE.
123    
124        The return value is a tuple with the projections in a ProjFile
125        object and a list of strings with warning messages. The warnings
126        list is usually empty but may contain messages about ignored errors.
127    
128      If the file could could not be opened return an empty projection      If the file could could not be opened return an empty projection
129      file object set to store data in the default file.      file object set to store data in the indicated default file.
130      """      """
131      filename = os.path.join(projdir, "defaults.proj")      fullname = os.path.join(projdir, filename)
132      try:      try:
133          return read_proj_file(filename)          return read_proj_file(fullname)
134      except (OSError, IOError, SAXParseException), val:      except (OSError, IOError, SAXParseException), val:
135          msg = _('Could not read "%s": %s') % (filename, str(val))          msg = _('Could not read "%s": %s') % (fullname, str(val))
136          return ProjFile(filename), [msg]          return ProjFile(fullname), [msg]
137    
138  def get_user_proj_file():  def get_user_proj_file():
139      """Return the user's projections and a list with warnings      """Return the user's projections and a list with warnings
# Line 132  class ProjFileReader(XMLReader): Line 178  class ProjFileReader(XMLReader):
178          if name is None:          if name is None:
179              name = _("Unknown")              name = _("Unknown")
180          self.name = name          self.name = name
181            self.epsg = self.encode(attrs.get((None, 'epsg')))
182    
183      def end_projection(self, name, qname):      def end_projection(self, name, qname):
184          try:          try:
185              proj = Projection(self.params, self.name)              proj = Projection(self.params, self.name, epsg = self.epsg)
186          except IOError, val:          except IOError, val:
187              self.warnings.append(_('Error in projection "%s": %s')              self.warnings.append(_('Error in projection "%s": %s')
188                                   % (self.name, str(val)))                                   % (self.name, str(val)))
# Line 173  class ProjFileSaver(XMLWriter): Line 220  class ProjFileSaver(XMLWriter):
220          self.open_element("projectionlist")          self.open_element("projectionlist")
221    
222          for p in pf.GetProjections():          for p in pf.GetProjections():
223              self.open_element("projection", {"name": p.GetName()})              attrs = {"name": p.GetName()}
224                if p.EPSGCode():
225                    attrs["epsg"] = p.EPSGCode()
226                self.open_element("projection", attrs)
227    
228              for param in p.GetAllParameters():              for param in p.GetAllParameters():
229                  self.write_element("parameter", {"value": param})                  self.write_element("parameter", {"value": param})
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