A plug-in for the JS map library Leaflet, allowing to define patterns (like dashes, arrows, icons, etc.) on Polylines.
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README.md

Leaflet PolylineDecorator

CDNJS

A Leaflet plug-in to define and draw patterns on existing Polylines or along coordinate paths.

Compatibility with Leaflet versions

The development version of the plugin (on the master branch) is targeted at the 1.x version of Leaflet.

For a version of the plugin compatible with the 0.7.x Leaflet release, use the leaflet-0.7.2 branch.

npm / bower

npm install leaflet-polylinedecorator
bower install leaflet-polylinedecorator

Features

  • Dashed or dotted lines, arrow heads, markers following line
  • Works on Polygons too! (easy, as Polygon extends Polyline)
  • Multiple patterns can be applied to the same line
  • New behaviors can be obtained by defining new symbols

Screenshot

screenshot

Usage

To create a decorator and add it to the map: L.polylineDecorator(latlngs, options).addTo(map);

  • latlngs can be one of the following types:

    • L.Polyline
    • L.Polygon
    • an array of L.LatLng, or with Leaflet's simplified syntax, an array of 2-cells arrays of coordinates (useful if you just want to draw patterns following coordinates, but not the line itself)
    • an array of any of these previous types, to apply the same patterns to multiple lines
  • options has a single property patterns, which is an array of Pattern objects.

Pattern definition

Property Type Required Description
offset see below No Offset of the first pattern symbol, from the start point of the line. Default: 0.
endOffset see below No Minimum offset of the last pattern symbol, from the end point of the line. Default: 0.
repeat see below Yes Repetition interval of the pattern symbols. Defines the distance between each consecutive symbol's anchor point.
symbol Symbol factory Yes Instance of a symbol factory class.

offset, endOffset and repeat can be each defined as a number, in pixels, or in percentage of the line's length, as a string (ex: '10%').

Methods

Method Description
setPaths(latlngs) Changes the path(s) the decorator applies to. latlngs can be all the types supported by the constructor. Useful for example if you remove polyline from a set, or coordinates change.
setPatterns(<Pattern[]> patterns) Changes the decorator's pattern definitions, and update the symbols accordingly.

Example

var polyline = L.polyline([...]).addTo(map);
var decorator = L.polylineDecorator(polyline, {
    patterns: [
        // defines a pattern of 10px-wide dashes, repeated every 20px on the line
        {offset: 0, repeat: 20, symbol: L.Symbol.dash({pixelSize: 10})}
    ]
}).addTo(map);

Performance note

Please note that this library is in an early stage, and many operations could still be optimized. Moreover, as it requires a lot of (re-)computations, and each pattern symbol is an actual L.ILayer object, it can have an impact on the responsiveness of your map, especially if used on many objects. In cases where it's applicable (dash patterns), you should probably use instead the dashArray property of L.Path, as it's natively drawn by the browser.