view release on metacpan or  search on metacpan

README  view on Meta::CPAN

NAME
    Geo::Google::PolylineEncoder - encode lat/lons to Google Maps Polylines

SYNOPSIS
      use Geo::Google::PolylineEncoder;

      my $points = [
                    # can also take points as [lat, lon]
                    { lat => 38.5, lon => -120.2 },
                    { lat => 40.7, lon => -120.95 },
                    { lat => 43.252, lon => -126.453 },
                   ];
      my $encoder = Geo::Google::PolylineEncoder->new;
      my $eline   = $encoder->encode( $points );
      print $eline->{num_levels};  # 18
      print $eline->{zoom_factor}; # 2
      print $eline->{points};      # _p~iF~ps|U_ulLnnqC_mqNvxq`@
      print $eline->{levels};      # POP

      # in Javascript, assuming eline was encoded as JSON:
      # ... load GMap2 ...
      var opts = {
        points: eline.points,
        levels: eline.levels,
        numLevels: eline.num_levels,
        zoomFactor: eline.zoom_factor,
      };
      var line = GPolyline.fromEncoded( opts );

DESCRIPTION
    This module encodes a list of lat/lon points representing a polyline
    into a format for use with Google Maps. This format is described here:

    http://code.google.com/apis/maps/documentation/polylinealgorithm.html

    The module is a port of Mark McClure's `PolylineEncoder.js' with some
    tweaks. The original can be found here:

    http://facstaff.unca.edu/mcmcclur/GoogleMaps/EncodePolyline/

CONSTRUCTOR & ACCESSORS
    new( [%args] )
        Create a new encoder. Arguments are optional and correspond to the
        accessor with the same name: the num_levels, zoom_factor,
        visible_threshold, and force_endpoints entries elsewhere in this
        document, etc...

        Note: there's nothing stopping you from setting these properties
        each time you encode a polyline.

    num_levels
        How many different levels of magnification the polyline has.
        Default: 18.

    zoom_factor
        The change in magnification between those levels (see num_levels).
        Default: 2.

    visible_threshold
        Indicates the length of a barely visible object at the highest zoom
        level. Default: 0.00001. err.. units.

    force_endpoints
        Indicates whether or not the endpoints should be visible at all zoom
        levels. force_endpoints is. Probably should stay true regardless.
        Default: 1=true.

    escape_encoded_points
        Indicates whether or not the encoded points should have escape
        characters escaped, eg:

          $points =~ s/\\/\\\\/g;

        This is useful if you'll be evalling the resulting strings, or
        copying them into a static document.

        Warning: don't turn this on if you'll be passing the encoded points
        straight on to your application, or you'll get unexpected results
        (ie: lines that start out right, but end up horribly wrong). It may
        even crash your browser.

        Default: 0=false.

    lons_first
        Specifies the order in which coordinates passed as arrayrefs to
        encode should be interpreted:

          # false: lat, lon
          $encoder->encode([
             [ 38.5, -120.2 ],
             [ 40.7, -120.95 ],
          ]);

          # true: lon, lat
          $encoder->encode([
             [ -120.2, 38.5 ],
             [ -120.95, 40.7 ],
          ]);

        Default: 0 = lat,lon

        (Yes, the default feels wrong to the mathematician in me, but that's
        how Google Maps do it, so for sake of consistency...)

METHODS
    encode( \@points );
        Encode the points into a string for use with Google Maps
        `GPolyline.fromEncoded' using a variant of the Douglas-Peucker
        algorithm to set levels, and the Polyline encoding algorithm defined
        by Google.

        Expects a reference to a `@points' array:

          [
           { lat => 38.5, lon => -120.2 },
           { lat => 40.7, lon => -120.95 },
           { lat => 43.252, lon => -126.453 },
          ];

        The individual points can also be given as arrayrefs:

          [
           [ 38.5, -120.2 ],
           [ 40.7, -120.95 ],
           [ 43.252, -126.453 ],