docs: def parse_options(args):
      """ Parses command line options """
      usage = 'usage: %prog [options] visio_filename image_filename'
      parser = OptionParser(usage=usage)
      parser.add_option('-p', '--page', action='store',
                        type='int', dest='pagenum',
                        help='pick a page by page number')
      parser.add_option('-n', '--name', action='store',
                        type='string', dest='pagename',
                        help='pick a page by page name')
      options, argv = parser.parse_args(args)
  
      if options.pagenum and options.pagename:
          parser.error('options --page and --name are mutually exclusive')
  
      if len(argv) != 2:
          parser.print_usage(sys.stderr)
          parser.exit()
  
      output_ext = os.path.splitext(argv[1])[1].lower()
      if output_ext not in ('.gif', '.jpg', '.png'):
          parser.error('Unsupported image format: %s' % argv[1])
  
      return options, argv