bin/wkt2kml

   1 #!/usr/bin/env python
   2
   3 """
   4 Convert an OGC Well-Known Text string to a Keyhole Markup Language
   5 (KML) file.
   6 """
   7
   8 """
   9 We take a Well-Known Text[1] string as input, and optionally a
  10 filename to which to write the output. While we shouldn't technically
  11 *need* access to a PostGIS database to perform this conversion, it
  12 makes everything a lot easier, so we require it.
  13
  14 There is prior art[2] (written in Perl) should we ever desire to do the
  15 conversions correctly, sans-database.
  16
  17 [1] http://en.wikipedia.org/wiki/Well-known_text
  18 [2] http://search.cpan.org/dist/Geo-Converter-WKT2KML/
  19 """
  20
  21 import os
  22 import pgdb
  23 import site
  24 import sys
  25
  26 # Basically, add '../src' to our path.
  27 # Needed for the imports that follow.
  28 site.addsitedir(os.path.dirname(os.path.abspath(sys.argv[0])) + '/../src')
  29
  30 import CLI
  31 import Configuration.Defaults
  32 import ExitCodes
  33 import GPS
  34 import SummaryFile1
  35 import KML
  36
  37
  38 """
  39 Parse the command line options. All of these are optional; defaults
  40 are provided for the database information and the output is written to
  41 stdout unless otherwise specified via '-o'.
  42
  43 We take an SRID too, in case there's ever a reason to override the
  44 default. The name option is available in case the user would like to
  45 e.g. see the object name in Google Earth.
  46 """
  47
  48 parser = CLI.default_option_parser()
  49
  50 # Use this module's docstring as the description.
  51 parser.description = __doc__.strip()
  52
  53 parser.add_option('-o',
  54                   '--outfile',
  55                   help='Optional output file path. Defaults to stdout.')
  56
  57 parser.add_option('-s',
  58                   '--srid',
  59                   help="SRID of the input geometry. Defaults to %s." % Configuration.Defaults.SRID,
  60                   default=Configuration.Defaults.SRID)
  61
  62 parser.add_option('-n',
  63                   '--name',
  64                   help='Name to give the geometry object in the KML document.',
  65                   default='WKT Object')
  66
  67 (options, args) = parser.parse_args()
  68
  69
  70 if len(args) < 1:
  71     print 'ERROR: You must provide a geometry object in Well-Known Text (WKT) format.'
  72     parser.print_help()
  73     print '' # Print a newline. Durrrr.
  74     raise SystemExit(ExitCodes.NOT_ENOUGH_ARGS)
  75
  76
  77 conn = pgdb.connect(host=options.host,
  78                     database=options.database,
  79                     user=options.username)
  80
  81 # We'll use this cursor for all of our queries.
  82 cursor = conn.cursor()
  83
  84
  85 # We use one query that basically just imports the WKT string and
  86 # immediately exports it as KML. The geometry must have an SRID when
  87 # ST_AsKml is called, so we provide one to ST_GeomFromText.
  88 kml_query = "SELECT ST_AsKml(ST_GeomFromText('%s', %s))" % (args[0], options.srid)
  89
  90 cursor.execute(kml_query)
  91 rows = cursor.fetchall()
  92 kml_representation = rows[0][0]
  93 conn.close()
  94
  95
  96 doc = KML.Document()
  97
  98 # Create a semi-transparent red polygon style, and add it to the
  99 # document.
 100 hex_value = "900000ff"
 101 s = KML.Style(initial_id=('default'))
 102 poly_style = KML.PolyStyle()
 103 color = KML.Color(hex_value)
 104 poly_style.children.append(color)
 105 s.children.append(poly_style)
 106 doc.styles.append(s)
 107
 108 # We're only going to have one placemark -- the object defined by our
 109 # input WKT.
 110
 111 placemark = KML.Placemark()
 112 name = KML.Name(options.name)
 113 placemark.children.append(name)
 114
 115 # This applies the red polygon style defined earlier to our placemark.
 116 styleurl = KML.StyleUrl('default')
 117 placemark.children.append(styleurl)
 118
 119 # The database query is going to give us raw KML. For example, if our
 120 # input WKT represents a polygon, the output of ST_AsKml will contain
 121 # <Polygon>...</Polygon> and everything therein.
 122 rawkml = KML.RawText(kml_representation)
 123 placemark.children.append(rawkml)
 124 doc.children.append(placemark)
 125
 126 # Default the output file to sys.stdout. If we were passed an outfile
 127 # as an argument, use that instead.
 128 output_file = sys.stdout
 129 if (options.outfile != None):
 130     output_file = open(options.outfile, 'w')
 131
 132 # Write the KML and get out of here.
 133 output_file.write(doc.to_kml())
 134 output_file.close()