Leaflet.LayerGroup.Collision
Provides basic collision detection in order to declutter large or overlapping sets of Leaflet markers.
Don't like READMEs? Then see http://mazemap.github.io/Leaflet.LayerGroup.Collision/demo/demo.html
What?
Inspired by the ClusterMarker plugin, this plugin works by hiding any markers that overlap each other - only the marker which was first added to the LayerGroup will be shown.
How?
Collision detection is done by using the dimensions of the DOM elements inside the L.Marker's icon; this has been tested only using display:block elements. L.Layers which are not markers will be always shown.
This plugin uses Vladimir Agafonkin's rbush library for the grunt work of detecting bounding box collisions.
Caveats: this plugin expects markers to not change dynamically, to not be draggable, and marker deletion is not supported (yet). Currently everything is recalculated on zoom change. Only partial data caching is done - marker bounding boxes are cached; collisions per zoom level are recalculated.
Usage
Works as a normal Leaflet LayerGroup, just add your markers to it.
When instantiating, can take the 'margin' option. This defines the margin between markers, in pixels, and defaults to zero.
var collisionLayer = L.layerGroup.collision({margin:5});
collisionLayer.addTo(map);
collisionLayer.add( L.marker( markeroptions ) );
This plugin also extends L.FeatureGroup into L.FeatureGroup.collision and L.GeoJSON into L.GeoJSON.collision.
Demo
There is a live demo at http://mazemap.github.io/Leaflet.LayerGroup.Collision/demo/demo.html
The demo loads about 1000 placenames, each of them being a L.DivIcon with two boxes.
The demo includes data from Natural Earth, which is public domain. Please visit http://www.naturalearthdata.com/downloads/10m-cultural-vectors/10m-populated-places/ for more information.
In order to try the demo locally, just clone the repo, run bower install (if using the gh-pages branch, use git clone --recursive instead to pull the rbush submodule), and see the file demo/demo.html. You can choose to load more or less data by commenting/uncommenting the lines that include the natural earth data files.