bin/drag_wkt_along_kml_path

   1 #!/usr/bin/env python
   2
   3 """
   4 We take a Well-Known Text string and a KML file as parameters. The WKT
   5 string is converted into a polygon (hopefully), and the KML file is
   6 parsed for a linestring, which defines a path. We then drag the
   7 polygon along the linestring, and return the resulting polygon as KML.
   8 """
   9
  10 import pgdb
  11 import os
  12 import site
  13 import sys
  14 from optparse import OptionParser
  15
  16 # Basically, add '../src' and '../lib/Shapely' to our path.
  17 # Needed for the imports that follow.
  18 site.addsitedir(os.path.dirname(os.path.abspath(sys.argv[0])) + '/../src')
  19 site.addsitedir(os.path.dirname(os.path.abspath(sys.argv[0])) + '/../lib/Shapely')
  20
  21 import Configuration.Defaults
  22 import ExitCodes
  23 import Geometry
  24 import KML
  25
  26 usage = '%prog [options] <well-known text> <kml filename>'
  27
  28 # -h (help) Conflicts with -h HOSTNAME
  29 parser = OptionParser(usage=usage, add_help_option = False)
  30
  31 # Use this module's docstring as the description.
  32 parser.description = __doc__.strip()
  33
  34 parser.add_option('-h',
  35                   '--host',
  36                   help='The hostname/address where the database is located.',
  37                   default=Configuration.Defaults.DATABASE_HOST)
  38
  39 parser.add_option('-d',
  40                   '--database',
  41                   help='The database in which the population data are stored.',
  42                   default=Configuration.Defaults.DATABASE_NAME)
  43
  44 parser.add_option('-U',
  45                   '--username',
  46                   help='The username who has access to the database.',
  47                   default=Configuration.Defaults.DATABASE_USERNAME)
  48
  49 parser.add_option('-o',
  50                   '--outfile',
  51                   help='Optional output file path. Defaults to stdout.')
  52
  53 parser.add_option('-n',
  54                   '--name',
  55                   help='Name to give the geometry object in the KML document.',
  56                   default='WKT Object')
  57
  58 parser.add_option('-s',
  59                   '--srid',
  60                   type="int",
  61                   help="SRID of the input geometry. Defaults to %s." % Configuration.Defaults.SRID,
  62                   default=Configuration.Defaults.SRID)
  63
  64 (options, args) = parser.parse_args()
  65
  66 if len(args) < 2:
  67     print """
  68 ERROR: You must supply both a Well-Known Text string, and a KML file
  69        containing a linestring.
  70 """
  71     parser.print_help()
  72     print '' # Print a newline
  73     raise SystemExit(ExitCodes.NOT_ENOUGH_ARGS)
  74
  75
  76 wkt_string = args[0]
  77 kml_filename = args[1]
  78
  79 f = open(kml_filename, 'r')
  80 kml = f.read()
  81 f.close()
  82
  83 coords = KML.LineString.tuples_from_kml(kml)
  84 p = Geometry.Polygon.from_wkt(wkt_string)
  85
  86 death_tube = None
  87
  88 for i in range(len(coords) - 1):
  89     # For each coordinate (except the last), we want to:
  90     # a) Translate our polygon to the coordinate.
  91     # b) Drag the polygon to the next coordinate.
  92     this_coord = Geometry.TwoVector(coords[i][0], coords[i][1])
  93     next_coord = Geometry.TwoVector(coords[i+1][0], coords[i+1][1])
  94     drag_vector = (next_coord - this_coord)
  95     tp = p.translate(this_coord)
  96
  97     if (death_tube == None):
  98         death_tube = tp.drag(drag_vector)
  99     else:
 100         death_tube = death_tube.union(tp.drag(drag_vector))
 101
 102
 103 conn = pgdb.connect(host=options.host,
 104                     database=options.database,
 105                     user=options.username)
 106
 107
 108 # We'll use this cursor for all of our queries.
 109 cursor = conn.cursor()
 110
 111
 112 # We use one query that basically just imports the WKT string and
 113 # immediately exports it as KML. The geometry must have an SRID when
 114 # ST_AsKml is called, so we provide one to ST_GeomFromText.
 115 kml_query = "SELECT ST_AsKml(ST_GeomFromText('%s', %s))" % (death_tube.wkt(), options.srid)
 116
 117 cursor.execute(kml_query)
 118 rows = cursor.fetchall()
 119 kml_representation = rows[0][0]
 120 conn.close()
 121
 122
 123 doc = KML.Document()
 124
 125 # Create a semi-transparent blue polygon style, and add it to the
 126 # document.
 127 hex_value = "b0ff0000"
 128 s = KML.Style(initial_id=('default'))
 129 poly_style = KML.PolyStyle()
 130 color = KML.Color(hex_value)
 131 poly_style.children.append(color)
 132 s.children.append(poly_style)
 133 doc.styles.append(s)
 134
 135 # We're only going to have one placemark -- the object defined by our
 136 # input WKT.
 137 placemark = KML.Placemark()
 138 name = KML.Name(options.name)
 139 placemark.children.append(name)
 140
 141 # This applies the red polygon style defined earlier to our placemark.
 142 styleurl = KML.StyleUrl('default')
 143 placemark.children.append(styleurl)
 144
 145 # The database query is going to give us raw KML. For example, if our
 146 # input WKT represents a polygon, the output of ST_AsKml will contain
 147 # <Polygon>...</Polygon> and everything therein.
 148 rawkml = KML.RawText(kml_representation)
 149 placemark.children.append(rawkml)
 150 doc.children.append(placemark)
 151
 152 # Default the output file to sys.stdout. If we were passed an outfile
 153 # as an argument, use that instead.
 154 output_file = sys.stdout
 155 if (options.outfile != None):
 156     output_file = open(options.outfile, 'w')
 157
 158 # Write the KML and get out of here.
 159 output_file.write(doc.to_kml())
 160 output_file.close()