@allmaps/maplibre

Allmaps plugin for MapLibre GL. This plugin allows displaying georeferenced IIIF images on a MapLibre map. The plugin works by loading Georeference Annotations and uses WebGL to transform images from a IIIF image server to overlay them on their correct geographical position. See allmaps.org for more information.

Examples:

• Observable notebook
• HTML example using ESM and Skypack
• HTML example using UMD and jsDelivr

How it works

This plugin creates a new class WarpedMapLayer which extends MapLibre's CustomLayerInterface. You can add one or multiple Georeference Annotations (or AnnotationPages with multiple Georeference Annotations) to a WarpedMapLayer, and add the WarpedMapLayer to your MapLibre map. This will render all georeferenced maps contained in the Georeference Annotation on your MapLibre map.

To understand what happens under the hood for each georeferenced map, see the @allmaps/render package.

Installation

This package works in browsers and in Node.js as an ESM or an UMD module.

Install with pnpm:

pnpm install @allmaps/maplibre

You can build this package locally by running:

pnpm run build

As an alternative to loading using import, ESM and UMD bundled versions of the code are also provided under /dist/bundled (once the code is built). These are also published online, so can load them directly in a HTML script tag using a CDN.

<script src="https://cdn.jsdelivr.net/npm/@allmaps/maplibre/dist/bundled/allmaps-maplibre-4.0.umd.js"></script>

When loading the bundled package, its classes are available under the Allmaps global variable:

const warpedMapLayer = new Allmaps.WarpedMapLayer()

Usage

Built for MapLibre 4.0, but should work with earlier versions as well.

Loading a Georeference Annotation

Creating a WarpedMapLayer and adding it to a map looks like this:

import { WarpedMapLayer } from '@allmaps/maplibre'

// MapLibre map with base layer
const map = new maplibregl.Map({
  container: 'map',
  style: 'https://basemaps.cartocdn.com/gl/voyager-gl-style/style.json',
  center: [-73.9337, 40.8011],
  zoom: 11.5,
  // Pitch is currently not supported by the Allmaps plugin for MapLibre
  maxPitch: 0,
  // This is needed to improve rendering
  // Future versions of the plugin might not need this
  preserveDrawingBuffer: true
})

const annotationUrl = 'https://annotations.allmaps.org/images/d180902cb93d5bf2'
const warpedMapLayer = new WarpedMapLayer()

map.on('load', () => {
  map.addLayer(warpedMapLayer)
  warpedMapLayer.addGeoreferenceAnnotationByUrl(annotationUrl)
})

WarpedMapLayer is implemented using MapLibre's CustomLayerInterface. It can be added to a map like any other MapLibre layer, but there are some things to take into account:

• WarpedMapLayer does not make use of a Source (although that could be implemented in the future, similar to @allmaps/openlayers).
• WarpedMapLayer currently does not support pitch, so disable it on your map.
• Just like other MapLibre layers, a WarpedMapLayer must have a unique id. By default, the id has the value warped-map-layer. When adding multiple WarpedMapLayers to your map, pass a unique id to their constructor:

const warpedMapLayerWithUniqueId = new WarpedMapLayer('my-unique-id')

A Georeference Annotation can be added to a WarpedMapLayer using the addGeoreferenceAnnotation and addGeoreferenceAnnotationByUrl functions:

fetch(annotationUrl)
  .then((response) => response.json())
  .then((annotation) => warpedMapLayer.addGeoreferenceAnnotation(annotation))

Or:

await warpedMapLayer.addGeoreferenceAnnotationByUrl(annotationUrl)

Events

The following events are emitted to inform you of the state of the WarpedMapLayer.

| Description | Type | Data | | ------------------------------------------------------------- | ------------------------- | ---------------------------------- | | A warped map has been added to the warped map list | warpedmapadded | mapId: string | | A warped map has been removed from the warped map list | warpedmapremoved | mapId: string | | A warped map enters the viewport | warpedmapenter | mapId: string | | A warped map leaves the viewport | warpedmapleave | mapId: string | | The visibility of some warpedMaps has changed | visibilitychanged | mapIds: string[] | | The cache loaded a first tile of a map | firstmaptileloaded | {mapId: string, tileUrl: string} | | All tiles requested for the current viewport have been loaded | allrequestedtilesloaded | |

You can listen to them in the typical MapLibre way. Here's an example:

warpedMapLayer.on('warpedmapadded', (event) => {
  console.log(event.mapId, warpedMapLayer.getBounds())
})

Some of the functions specified in the API only make sense once a warped map is loaded into the WarpedMapLayer. You can use such listeners to make sure function are run e.g. only after a warped map has been added.

What is a map?

A MapLibre map is an instance of the MapLibre Map class, the central class of the MapLibre API, used to create a map on a page and manipulate it.

In Allmaps there are multiple classes describing maps, one for each phase a map takes through the Allmaps rendering pipeline:

• When a Georeference Annotation is parsed, an instance of the Georeferenced Map class is created from it.
• When this map is loaded into an application for rendering, an instance of the Warped Map class is created from it.
• Inside the WebGL2 rendering package, the WebGL2WarpedMap class is used to render the map.

All these map phases originating from the same Georeference Annotation have the same unique mapId property. This string value is used though-out Allmaps (and in the API below) to identify a map. It is returned after adding a georeference annotation to a warpedMapLayer, so you can use it later to call functions on a specific map.

API

Table of Contents

• WarpedMapLayer
  • onAdd
  • onRemove
  • addGeoreferenceAnnotation
  • removeGeoreferenceAnnotation
  • addGeoreferenceAnnotationByUrl
  • removeGeoreferenceAnnotationByUrl
  • addGeoreferencedMap
  • removeGeoreferencedMap
  • getWarpedMapList
  • getWarpedMap
  • showMap
  • showMaps
  • hideMap
  • hideMaps
  • isMapVisible
  • setMapResourceMask
  • setMapsTransformationType
  • setMapsDistortionMeasure
  • getBounds
  • bringMapsToFront
  • sendMapsToBack
  • bringMapsForward
  • sendMapsBackward
  • getMapZIndex
  • setImageInformations
  • getOpacity
  • setOpacity
  • resetOpacity
  • getMapOpacity
  • setMapOpacity
  • resetMapOpacity
  • setSaturation
  • resetSaturation
  • setMapSaturation
  • resetMapSaturation
  • setRemoveColor
  • resetRemoveColor
  • setMapRemoveColor
  • resetMapRemoveColor
  • setColorize
  • resetColorize
  • setMapColorize
  • resetMapColorize
  • clear
  • preparerender
  • render

WarpedMapLayer

WarpedMapLayer class.

This class renders maps from a IIIF Georeference Annotation on a MapLibre map. WarpedMapLayer is implemented using MapLibre's CustomLayerInterface.

onAdd

Method called when the layer has been added to the Map.

Parameters

• map Map The Map this custom layer was just added to.
• gl WebGL2RenderingContext The WebGL 2 context for the map.

onRemove

Method called when the layer has been removed from the Map.

addGeoreferenceAnnotation

Adds a Georeference Annotation.

Parameters

• annotation any Georeference Annotation

Returns Promise<Array<(string | Error)>> the map IDs of the maps that were added, or an error per map

removeGeoreferenceAnnotation

Removes a Georeference Annotation.

Parameters

• annotation any Georeference Annotation

Returns Promise<Array<(string | Error)>> the map IDs of the maps that were removed, or an error per map

addGeoreferenceAnnotationByUrl

Adds a Georeference Annotation by URL.

Parameters

• annotationUrl string Georeference Annotation

Returns Promise<Array<(string | Error)>> the map IDs of the maps that were added, or an error per map

removeGeoreferenceAnnotationByUrl

Removes a Georeference Annotation by URL.

Parameters

• annotationUrl string Georeference Annotation

Returns Promise<Array<(string | Error)>> the map IDs of the maps that were removed, or an error per map

addGeoreferencedMap

Adds a Georeferenced map.

Parameters

• georeferencedMap unknown Georeferenced map

Returns Promise<(string | Error)> the map ID of the map that was added, or an error

removeGeoreferencedMap

Removes a Georeferenced map.

Parameters

• georeferencedMap unknown Georeferenced map

Returns Promise<(string | Error)> the map ID of the map that was remvoed, or an error

getWarpedMapList

Returns the WarpedMapList object that contains a list of the warped maps of all loaded maps

Returns WarpedMapList the warped map list

getWarpedMap

Returns a single map's warped map

Parameters

• mapId string ID of the map

Returns (WebGL2WarpedMap | undefined) the warped map

showMap

Make a single map visible

Parameters

• mapId string ID of the map

showMaps

Make multiple maps visible

Parameters

• mapIds Iterable<string> IDs of the maps

hideMap

Make a single map invisible

Parameters

• mapId string ID of the map

hideMaps

Make multiple maps invisible

Parameters

• mapIds Iterable<string> IDs of the maps

isMapVisible

Returns the visibility of a single map

Parameters

• mapId

Returns (boolean | undefined) whether the map is visible

setMapResourceMask

Sets the resource mask of a single map

Parameters

• mapId string ID of the map
• resourceMask Ring new resource mask

setMapsTransformationType

Sets the transformation type of multiple maps

Parameters

• mapIds Iterable<string> IDs of the maps
• transformation TransformationType new transformation type

setMapsDistortionMeasure

Sets the distortion measure of multiple maps

Parameters

• mapIds Iterable<string> IDs of the maps
• distortionMeasure DistortionMeasure new transformation type

getBounds

Return the bounding box of all visible maps in the layer (inside or outside of the Viewport), in longitude/latitude coordinates.

Returns (Bbox | undefined) bounding box of all warped maps

bringMapsToFront

Bring maps to front

Parameters

• mapIds Iterable<string> IDs of the maps

sendMapsToBack

Send maps to back

Parameters

• mapIds Iterable<string> IDs of the maps

bringMapsForward

Bring maps forward

Parameters

• mapIds Iterable<string> IDs of the maps

sendMapsBackward

Send maps backward

Parameters

• mapIds Iterable<string> IDs of the maps

getMapZIndex

Returns the z-index of a single map

Parameters

• mapId string ID of the warped map

Returns (number | undefined) z-index of the warped map

setImageInformations

Sets the object that caches image information

Parameters

• imageInformations ImageInformations Object that caches image information

getOpacity

Gets the opacity of the layer

Returns (number | undefined) opacity of the map

setOpacity

Sets the opacity of the layer

Parameters

• opacity number opacity between 0 and 1, where 0 is fully transparent and 1 is fully opaque

resetOpacity

Resets the opacity of the layer to fully opaque

getMapOpacity

Gets the opacity of a single map

Parameters

• mapId string ID of the map

Returns (number | undefined) opacity of the map

setMapOpacity

Sets the opacity of a single map

Parameters

• mapId string ID of the map
• opacity number opacity between 0 and 1, where 0 is fully transparent and 1 is fully opaque

resetMapOpacity

Resets the opacity of a single map to fully opaque

Parameters

• mapId string ID of the map

setSaturation

Sets the saturation of a single map

Parameters

• saturation number saturation between 0 and 1, where 0 is grayscale and 1 are the original colors

resetSaturation

Resets the saturation of a single map to the original colors

setMapSaturation

Sets the saturation of a single map

Parameters

• mapId string ID of the map
• saturation number saturation between 0 and 1, where 0 is grayscale and 1 are the original colors

resetMapSaturation

Resets the saturation of a single map to the original colors

Parameters

• mapId string ID of the map

setRemoveColor

Removes a color from all maps

Parameters

• options Object remove color options

  • options.hexColor string? hex color to remove
  • options.threshold number? threshold between 0 and 1
  • options.hardness number? hardness between 0 and 1

resetRemoveColor

Resets the color removal for all maps

setMapRemoveColor

Removes a color from a single map

Parameters

• mapId string ID of the map

• options Object remove color options

  • options.hexColor string? hex color to remove
  • options.threshold number? threshold between 0 and 1
  • options.hardness number? hardness between 0 and 1

resetMapRemoveColor

Resets the color for a single map

Parameters

• mapId string ID of the map

setColorize

Sets the colorization for all maps

Parameters

• hexColor string desired hex color

resetColorize

Resets the colorization for all maps

setMapColorize

Sets the colorization for a single mapID of the map

Parameters

• mapId string ID of the map
• hexColor string desired hex color

resetMapColorize

Resets the colorization of a single map

Parameters

• mapId string ID of the map

clear

Removes all warped maps from the layer

preparerender

Prepare rendering the layer.

render

Render the layer.