leaflet-side-by-side

A Leaflet control to add a split screen to compare two map overlays.

L.control.sideBySide(leftLayer[s], rightLayer[s])

Creates a new Leaflet Control for comparing two layers or collections of layers. It does not add the layers to the map - you need to do that manually. Extends L.Control but setPosition() and getPosition are noop because the position is always the same - it does not make sense for this control to be in the corner like other Leaflet controls.

Parameters

parameter	type	description
leftLayers	L.Layer|array	A Leaflet Layer or array of layers to show on the left side of the map. Any layer added to the map that is in this array will be shown on the left
rightLayers	L.Layer|array	A Leaflet Layer or array of layers to show on the right side of the map. Any layer added to the map that is in this array will be shown on the right. These should not be the same as any layers in leftLayers
options	Object	Options
options.padding	Number	Padding between slider min/max and the edge of the screen in pixels. Defaults to 30 - the width of the slider thumb
options.swap	Boolean	Should display swap button, when both layers available

Events

Subscribe to events using these methods

Event	Data	Description
leftlayeradd	LayerEvent	Fired when a layer is added to the left-hand-side pane
leftlayerremove	LayerEvent	Fired when a layer is removed from the left-hand-side pane
rightlayeradd	LayerEvent	Fired when a layer is added to the right-hand-side pane
rightlayerremove	LayerEvent	You guessed it... fired when a layer is removed from the right-hand-side pane
dividermove	{ x: number }	Fired when the divider is moved. Argument is an event object with the property x = the pixels of the divider from the left side of the map container.
swapped	{ swapped: boolean}	Fired when ths swap button clicked. Argument is an event object with the property swapped = the current status of swapping.

Methods

Method	Returns	Description
setLeftLayers	this	Set the layer(s) for the left side
setRightLayers	this	Set the layer(s) for the right side

Usage

Add the script to the top of your page (css is included in the javascript):

<script src="leaflet-side-by-side.js"></script>

Or if you are using browserify:

var sideBySide = require('leaflet-side-by-side')

For tile layers create a map, add two layers to it, and create the SideBySide control and add it to the map:

var map = L.map('map').setView([51.505, -0.09], 13);

var myLayer1 = L.tileLayer(...).addTo(map);

var myLayer2 = L.tileLayer(...).addTo(map)

L.control.sideBySide(myLayer1, myLayer2).addTo(map);

For image overlays create a map pane for each layer, create a SideBySide control and add it to the map:

var map = L.map('map').setView([23.140, -101.887], 5);

map.createPane('left');
map.createPane('right');

var imgUrl1 = '...',
imageBounds = [[7.9409, -131.1589], [29.2144, -82.6558]];
var leftLayer = L.imageOverlay(imgUrl1, imageBounds, {pane: 'left'}).addTo(map);

var imgUrl2 = '...',
imageBounds = [[7.9409, -131.1589], [29.2144, -82.6558]];
var imgUrl2 = L.imageOverlay(imgUrl2, imageBounds, {pane: 'right'}).addTo(map);

L.control.sideBySide(leftLayer, rightLayer).addTo(map);

Examples

• Live TileLayer Example see source
• Live ImageOverlay Example see source

Limitations

• The divider is not movable with IE.
• Probably won't work in IE8, but what does?

License

MIT