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leaflet.wms.js

An all-in-one WMS plugin for Leaflet.

Leaflet is great for tiled maps, but has limited support for WMS. This is by design: after all, the core motivation for Leaflet is to make the basic things work perfectly and not to support every use case.

That said, there are still use cases where more robust WMS support is needed. For example, small scale applications (e.g. for local governments) that integrate multiple custom WMS layers from one source. Loading these layers individually via L.TileLayer.WMS is problematic:

  • The default tile size will result in many duplicate labels for vector-backed layers.
  • The browser can be overwhelmed when using a large tile size or displaying many layers at once.

Various workarounds have been proposed to address some of these issues, most notably in Leaflet.NonTiledLayer. The goal of this project to bring all of these concepts and more into a single, comprehensive WMS plugin for Leaflet.

Demo

Features

  • "Single-tile" auto-updating WMS overlay
  • Use single server-composited image for layers coming from the same source
  • Layer identify via GetFeatureInfo
  • Pull requests welcome!

Note: this plugin officially only works with Leaflet 1.0. There is an unsupported patch that works with Leaflet 0.7, though it's not kept up to date.

Usage

// Default usage (uses L.WMS.Overlay)
var source = L.WMS.source("http://example.com/mapserv", {
    'transparent': true
});
source.getLayer("layer1").addTo(map);
source.getLayer("layer2").addTo(map);

// Tile mode (Uses L.WMS.TileLayer)
var s = L.WMS.source("http://example.com/mapserv", {
    'transparent': true,
    'tiled': true
});
source.getLayer("layer1").addTo(map);
source.getLayer("layer2").addTo(map);

leaflet.wms can be loaded via AMD, CommonJS/Node, and browser global environments.

// AMD example
define(['leaflet', 'leaflet.wms'],
function(L, wms) {

// L.WMS === wms;
var source = wms.source("http://example.com/mapserv");

});

API

leaflet.wms provides four layer classes (and shortcut lowercase functions) that facilitate working with WMS layers. To get the most out of leaflet.wms, it's generally best to just use the L.WMS.Source virtual layer, which creates other layers automatically.

L.WMS.TileLayer

This class is (currently) identical to L.TileLayer.WMS. It provides a simple interface for loading tiles from a WMS service.

var tiles = L.WMS.tileLayer("http://example.com/mapserv", {
    'tileSize': 512,
    'layers': 'layer1,layer2',
    'transparent': true
});
tiles.addTo(map);

L.WMS.Overlay

This class provides a "single-tile"/untiled/non-tiled WMS layer. Every time the map is panned or zoomed, a new WMS image will be requested for the entire display. To make transitions smoother, the existing image will be kept visible until the new one is loaded. An internal L.ImageOverlay instance is created for this purpose. (This technique was inspired by the esri-leaflet plugin.)

The API is nearly identical to L.WMS.TileLayer, except that the tile options do not apply.

var overlay = L.WMS.overlay("http://example.com/mapserv", {
    'layers': 'layer1,layer2',
    'transparent': true
});
overlay.addTo(map);

L.WMS.Source

L.WMS.Source is a virtual Leaflet "layer" that manages multiple WMS layers coming from a single WMS source. By using the same source for multiple layers, you can have the WMS service composite the image, and avoid overloading the client with multiple large images. L.WMS.Source is a virtual layer, as it does not load the WMS image directly. Instead, it creates an internal L.WMS.Overlay or L.WMS.TileLayer to handle the actual loading.

Like the other WMS layers, L.WMS.Source takes a URL and an options object as initialization parameters. The options are passed on to the underlying Overlay or TileLayer. An additional option, untiled, toggles whether to use Overlay or TileLayer. The default is true, which uses the non-tiled Overlay. Unless your WMS service is optimized for tiling, the default should provide the best performance. To use the TileLayer, set untiled to false. You can also set tiled to true, which will both use the TileLayer backend and set tiled=true in the WMS request (see #16.

L.WMS.Source provides two functions for toggling on and off individual WMS layers (addSubLayer and removeSubLayer, respectively). That said, it is usually more convenient to use L.WMS.Layer instances (described next).

var options = {'transparent': true};
var source = L.WMS.source("http://example.com/mapserv", options);
source.addSubLayer('layer1');
source.addTo(map);

L.WMS.Layer

L.WMS.Layer is a virtual Leaflet "layer" that facilitates Leaflet-style operations on individual WMS layers. For example, you can "add" a L.WMS.Layer to a map, and the corresponding Source will automatically be updated (instead of actually adding a new overlay to the map). L.WMS.Layer is particularly useful in conjunction with Leaflet's built in layer control. L.WMS.Layer takes three arguments: a source, a layerName, and the WMS options object. The source can be a source object or a URL. If a URL is given, a source object will be created from the URL if it doesn't exist already.

For convenience, L.WMS.Source provides a getLayer function that will generate a L.WMS.Layer already bound to the source object. It's usually better to use this feature instead of creating L.WMS.Layer instances directly.

// Okay (implicit source)
var options = {'transparent': true};
var layer1 = L.WMS.layer("http://example.com/mapserv", "layer1", options);
var layer2 = L.WMS.layer("http://example.com/mapserv", "layer2", options);
// layer1._source === layer2._source
var control = L.control.layers({}, {
    'Layer 1': layer1,
    'Layer 2': layer2
})
control.addTo(map);
// Recommended (explicit source)
var options = {'transparent': true};
var source = L.WMS.source("http://example.com/mapserv", options);
var layer1 = source.getLayer('layer1');
var layer2 = source.getLayer('layer2');
var control = L.control.layers({}, {
    'Layer 1': layer1,
    'Layer 2': layer2
})
control.addTo(map);

Identify (GetFeatureInfo)

L.WMS.Source includes an identify() feature that can call the WMS GetFeatureInfo service to query a map layer and return information about the underlying features. To disable this functionality, set options.identify to false when initializing the source. The default functionality places a popup on the map at the point where the user clicked. To customize the functionality, create a class extending L.WMS.Source and override one or more of the provided hooks.

var MySource = L.WMS.Source.extend({
    'ajax': function(url, callback) {
        $.ajax(url, {
            'context': this,
            'success': function(result) {
                callback.call(this, result);
             }
        });
    },
    'showFeatureInfo': function(latlng, info) {
        $('.output').html(info);
    }
});

The following hooks are available:

Name Description
getIdentifyLayers() Determine which layers to identify (default is all visible layers)
getFeatureInfoParams(point, layers) Generate parameters for WMS GetFeatureInfo request
ajax(url, callback) Actual AJAX call. The default implementation is a rudimentary XMLHttpRequest wrapper. Override this if you want to use jQuery or something with more robust support for older browsers. If you override this, be sure to preserve the value of this when calling the callback function (e.g. callback.call(this, result)).
parseFeatureInfo(result, url) Parse the AJAX response into HTML
showFeatureInfo(latlng, info) Display parsed AJAX response to the user (e.g in a popup)
showWaiting() Start AJAX wait animation (spinner, etc.)
hideWaiting() Stop AJAX wait animation