Leaflet MaskCanvas

A leaflet canvas layer for displaying large coverage data sets.

Features:

• Canvas tile layer based
• High performance even for large dataset because of the QuadTree that is used internally
• Custom color and circle size

Demo

Check out the demo at http://domoritz.github.com/vbb-coverage/.

Usage

Set up

• Add the MaskCanvas and Quadtree libraries.

<script src="QuadTree.js"></script>
<script src="L.TileLayer.MaskCanvas.js"></script>

You can also use the following package managers

• npm npm install leaflet.maskcanvas
• bower bower install leaflet.maskcanvas

Initialize the maskCanvas layer

L.TileLayer.maskCanvas();

Set the dataset for the layer.

layer.setData(data);

Finally add the layer to the map.

map.addLayer(layer);

The data format is a simple array of [lat, lng] pairs. For example [[51.50,-0.28],[51.51,-0.07],[51.51,-0.07],[51.54,-0.29]]. I recommend that you load the data set asynchronously in order to keep the page responsive. Once the data is loaded, you can add it to the layer and display it.

Possible options

The MaskCanvas layer supports all Leaflet canvas layer options which can be passed to L.TileLayer.maskCanvas. You probably want to set the layer opacity.

Other possible options:

var layer = L.TileLayer.maskCanvas({
       radius: 5,  // radius in pixels or in meters (see useAbsoluteRadius)
       useAbsoluteRadius: true,  // true: r in meters, false: r in pixels
       color: '#000',  // the color of the layer
       opacity: 0.5,  // opacity of the not covered area
       noMask: false,  // true results in normal (filled) circled, instead masked circles
       lineColor: '#A00'   // color of the circle outline if noMask is true
});

Leaflet 1.0

For the upcoming leaflet version there is a slightly changed implementation based on L.GridLayer. All you need to do, is replace L.TileLayer.maskCanvas with L.GridLayer.maskCanvas.

The new L.GridLayer.maskCanvas for leaflet 1.0 supports the same options as before. Additionally it allows you to specify different radii for each data point as you can see in the example at http://loggia.at/leaflet-maskcanvas/demo/index-1.0-dev.html

Screenshot

Developers

Run the demo locally with python -m SimpleHTTPServer and then open http://0.0.0.0:8000/demo.

Acknowledgement

The QuadTree implementation comes from https://github.com/jsmarkus/ExamplesByMesh/tree/master/JavaScript/QuadTree and has been slightly modified. Original Implementation by Mike Chambers.