NAME:
Geo::Heatmap

overlay a density map (aka heatmap) over googlemaps

see example here

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

GET CODE
https://github.com/MarkHofstetter/GoogleMapsHeatmap

SYNOPSIS
Create a Heatmap layer for GoogleMaps

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,
} );

$ghm->cache($cache);
$ghm->return_points( \&get_points );
my $image = $ghm->tile($tile);


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
is 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