Mark Hofstetter > Geo-Heatmap-0.18 > Geo::Heatmap

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Module Version: 0.18   Source  

NAME ^

Geo::Heatmap - generate a density map (aka heatmap) overlay layer for Google Maps, see the www directory in the distro how it works

see the script directory for creating a scale

for a real life example see

http://www.trust-box.at/dev/gm/GoogleMapsHeatmap/www/GoogleMapsHeatmap.html

for Dokumentation see

HOMEPAGE ^

http://www.trust-box.at/googlemaps-geoheatmap/

REQUIRES ^

  Moose
  CHI
  Imager

METHODS ^

tile

  tile();

  return the tile image in png format

ATTRIBUTES ^

  debug
  cache
  logfile
  return_points
  zoom_scale
  palette

USAGE

Create a Heatmap layer for GoogleMaps

The HTML part


  <head>
     <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
     <style type="text/css">
       html { height: 100% }
       body { height: 100%; margin: 0; padding: 0 }
       #map-canvas { height: 100% }
     </style>
     <script type="text/javascript"
       src="https://maps.googleapis.com/maps/api/js?key=&sensor=true">
     </script>
     <script type="text/javascript">
       var overlayMaps = [{
         getTileUrl: function(coord, zoom) {
           return "hm.fcgi?tile="+coord.x+"+"+coord.y+"+"+zoom;
         },


         tileSize: new google.maps.Size(256, 256),
         isPng: true,
         opacity: 0.4
       }];
 
       function initialize() {
         var mapOptions = {
           center: new google.maps.LatLng(48.2130, 16.375),
           zoom: 9
         };
         var map = new google.maps.Map(document.getElementById("map-canvas"),
             mapOptions);
 
       var overlayMap = new google.maps.ImageMapType(overlayMaps[0]);
       map.overlayMapTypes.setAt(0,overlayMap);
 
       }
       google.maps.event.addDomListener(window, 'load', initialize);
 
     </script>
   </head>
   <body>
     <div id="map-canvas"/>
  </body>


The (f)cgi part


  #!/usr/bin/env perl


  use strict;
  use FCGI;
  use DBI;
  use CHI;
  use FindBin qw/$Bin/;
  use lib "$Bin/../lib";
  
  use Geo::Heatmap;
  
  #my $cache = CHI->new( driver  => 'Memcached::libmemcached',
  #    servers    => [ "127.0.0.1:11211" ],
  #    namespace  => 'GoogleMapsHeatmap',
  #);
  
  
  my $cache = CHI->new( driver => 'File',
           root_dir => '/tmp/GoogleMapsHeatmap'
       );
  
  
  our $dbh = DBI->connect("dbi:Pg:dbname=gisdb", 'gisdb', 'gisdb', {AutoCommit => 0});
  
  my $request = FCGI::Request();
  
  while ($request->Accept() >= 0) {
    my $env = $request->GetEnvironment();
    my $p = $env->{'QUERY_STRING'};
  
    my ($tile) = ($p =~ /tile=(.+)/);
    $tile =~ s/\+/ /g;
  
    # package needs a CHI Object for caching
    #               a Function Reference to get LatLOng within a Google Tile
    #               maximum number of points per zoom level
  
    my $ghm = Geo::Heatmap->new();
    $ghm->palette('palette.store');
    $ghm->zoom_scale( {
      1 => 298983,
      2 => 177127,
      3 => 104949,
      4 => 90185,
      5 => 70338,
      6 => 37742,
      7 => 28157,
      8 => 12541,
      9 => 3662,
      10 => 1275,
      11 => 417,
      12 => 130,
      13 => 41,
      14 => 18,
      15 => 10,
      16 => 6,
      17 => 2,
      18 => 0,
    } );
  
  sub get_points {
    my $r = shift;
  
    my $sth = $dbh->prepare( qq(select ST_AsEWKT(geom) from geodata
                           where geom &&
                ST_SetSRID(ST_MakeBox2D(ST_Point($r->{LATN}, $r->{LNGW}),
                                        ST_Point($r->{LATS}, $r->{LNGE})
                          ),4326))
                );
  
    $sth->execute();
  
    my @p;
    while (my @r = $sth->fetchrow) {
      my ($x, $y) = ($r[0] =~/POINT\((.+?) (.+?)\)/);
      push (@p, [$x ,$y]);
    }
    $sth->finish;
    return \@p;
  }
  
  

You need a color palette (one is included) to encode values to colors, in Storable Format as an arrayref of arrayrefs eg

    [50] = [34, 45, 56]

which means that a normalized value of 50 would lead to an RGB color of 34% red , 45% blue, 56% green.

zoom_scale

The maximum number of points for a given google zoom scale. You would be able to extract to values from the denisity log or derive them from your data in some cunning way

cache

You need some caching for the tiles otherwise the map would be quite slow. Use a CHI object with the cache you like

return_points

A function reference which expects a single hashref as a parameter which defines two LAT/LONG points to get all data points within this box:

      $r->{LATN}, $r->{LNGW}), $r->{LATS}, $r->{LNGE}

The function has to return an arrayref of arrayrefs of the points within the box

tile

Returns the rendered image

REPOSITORY ^

https://github.com/MarkHofstetter/GoogleMapsHeatmap

AUTHOR ^

Mark Hofstetter <hofstettm@cpan.org>

  Thanks to 
  brian d foy
  Marcel Gruenauer
  David Steinbrunner

TODO ^

COPYRIGHT AND LICENSE ^

This software is copyright (c) 2013 by Mark Hofstetter

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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