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 from optparse import OptionParser
  22 import os
  23 import pgdb
  24 import site
  25 import sys
  26
  27 # Basically, add '../src' to our path.
  28 # Needed for the imports that follow.
  29 site.addsitedir(os.path.dirname(os.path.abspath(sys.argv[0])) + '/../src')
  30
  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 # -h (help) Conflicts with -h HOSTNAME
  49 parser = OptionParser(add_help_option = False)
  50
  51 # Use this module's docstring as the description.
  52 parser.description = __doc__.strip()
  53
  54 parser.add_option('-h',
  55                   '--host',
  56                   help='The hostname/address where the database is located.',
  57                   default=Configuration.Defaults.DATABASE_HOST)
  58
  59 parser.add_option('-d',
  60                   '--database',
  61                   help='The database in which the population data are stored.',
  62                   default=Configuration.Defaults.DATABASE_NAME)
  63
  64 parser.add_option('-U',
  65                   '--username',
  66                   help='The username who has access to the database.',
  67                   default=Configuration.Defaults.DATABASE_USERNAME)
  68
  69 parser.add_option('-o',
  70                   '--outfile',
  71                   help='Optional output file path. Defaults to stdout.')
  72
  73 parser.add_option('-s',
  74                   '--srid',
  75                   help="SRID of the input geometry. Defaults to %s." % Configuration.Defaults.SRID,
  76                   default=Configuration.Defaults.SRID)
  77
  78 parser.add_option('-n',
  79                   '--name',
  80                   help='Name to give the geometry object in the KML document.',
  81                   default='WKT Object')
  82
  83 (options, args) = parser.parse_args()
  84
  85
  86 if len(args) < 1:
  87     print 'ERROR: You must provide a geometry object in Well-Known Text (WKT) format.'
  88     parser.print_help()
  89     print '' # Print a newline. Durrrr.
  90     raise SystemExit(ExitCodes.NOT_ENOUGH_ARGS)
  91
  92
  93 conn = pgdb.connect(host=options.host,
  94                     database=options.database,
  95                     user=options.username)
  96
  97 # We'll use this cursor for all of our queries.
  98 cursor = conn.cursor()
  99
 100
 101 # We use one query that basically just imports the WKT string and
 102 # immediately exports it as KML. The geometry must have an SRID when
 103 # ST_AsKml is called, so we provide one to ST_GeomFromText.
 104 kml_query = "SELECT ST_AsKml(ST_GeomFromText('%s', %s))" % (args[0], options.srid)
 105
 106 cursor.execute(kml_query)
 107 rows = cursor.fetchall()
 108 kml_representation = rows[0][0]
 109 conn.close()
 110
 111
 112 doc = KML.Document()
 113
 114 # Create a semi-transparent red polygon style, and add it to the
 115 # document.
 116 hex_value = "900000ff"
 117 s = KML.Style(initial_id=('default'))
 118 poly_style = KML.PolyStyle()
 119 color = KML.Color(hex_value)
 120 poly_style.children.append(color)
 121 s.children.append(poly_style)
 122 doc.styles.append(s)
 123
 124 # We're only going to have one placemark -- the object defined by our
 125 # input WKT.
 126
 127 placemark = KML.Placemark()
 128 name = KML.Name(options.name)
 129 placemark.children.append(name)
 130
 131 # This applies the red polygon style defined earlier to our placemark.
 132 styleurl = KML.StyleUrl('default')
 133 placemark.children.append(styleurl)
 134
 135 # The database query is going to give us raw KML. For example, if our
 136 # input WKT represents a polygon, the output of ST_AsKml will contain
 137 # <Polygon>...</Polygon> and everything therein.
 138 rawkml = KML.RawText(kml_representation)
 139 placemark.children.append(rawkml)
 140 doc.children.append(placemark)
 141
 142 # Default the output file to sys.stdout. If we were passed an outfile
 143 # as an argument, use that instead.
 144 output_file = sys.stdout
 145 if (options.outfile != None):
 146     output_file = open(options.outfile, 'w')
 147
 148 # Write the KML and get out of here.
 149 output_file.write(doc.to_kml())
 150 output_file.close()