From: Michael Orlitzky <michael@orlitzky.com>
Date: Thu, 4 Mar 2010 19:34:30 +0000 (-0500)
Subject: Added the wkt_n-gon script.
X-Git-Url: http://gitweb.michael.orlitzky.com/?p=dead%2Fcensus-tools.git;a=commitdiff_plain;h=c62d089df5a523ff0cd87b2a71e5be3e9ab337bf

Added the wkt_n-gon script.
---

diff --git a/bin/wkt_n-gon b/bin/wkt_n-gon
new file mode 100755
index 0000000..947b03a
--- /dev/null
+++ b/bin/wkt_n-gon
@@ -0,0 +1,74 @@
+#!/usr/bin/python
+
+"""
+Output the Well-Known-Text[1] representation of an n-gon, centered at
+(0,0).
+
+The parameter n is passed as a required command-line option. The
+radius of the n-gon is an optional argument.
+
+[1] http://en.wikipedia.org/wiki/Well-known_text
+"""
+
+import math
+import site
+import sys
+from optparse import OptionParser
+import os
+
+# Basically, add '../src' to our path.
+# Needed for the imports that follow.
+site.addsitedir(os.path.dirname(os.path.abspath(sys.argv[0])) + '/../src')
+
+import CLI
+import ExitCodes
+import Geometry
+import StringUtils
+
+usage = '%prog [options] <number of sides>'
+fmtr = CLI.VerbatimHelpFormatter()
+parser = OptionParser(usage, formatter=fmtr)
+
+# Use this module's docstring as the description.
+parser.description = __doc__
+
+
+parser.add_option('-r',
+                  '--radius',
+                  type="float",
+                  help="The radius of the n-gon. Defaults to 1.0.",
+                  default=1.0)
+
+
+(options, args) = parser.parse_args()
+
+if (len(args) < 1) or (not StringUtils.is_integer(args[0])):
+    print "\nERROR: You must supply the number of sides, n.\n"
+    parser.print_help()
+    print '' # Print a newline.
+    raise SystemExit(ExitCodes.NOT_ENOUGH_ARGS)
+
+# The conversion of n to int is safe, since it passed is_integer
+# above.
+n = int(args[0])
+r = options.radius
+
+# Each new coordinate is going to be separated from the previous by
+# angle_delta radians.
+angle_delta = 2*math.pi / float(n)
+
+# The set of coordinates, as two-tuples. We already know the first
+# one--it's just cos/sin of 0.
+coords = [(r, 0)]
+
+for coord_idx in range(1, n):
+    angle = coord_idx * angle_delta    
+    x = r * math.cos(angle)
+    y = r * math.sin(angle)
+    coords.append((x, y))
+
+# A well-known-text polygon must be closed, i.e. the last coordinate
+# must equal the first. So, we're missing a coordinate, but the
+# Polygon class will handle it for us.
+p = Geometry.Polygon(coords)
+print p.wkt()