Feature: Terrain Preview and simple Elevation Query (#1425)

* add terrain preview and elevation link

* add elevation api for terrain tiles

* add documentation for elevation api

* applied lint:js:fix

* Add `test-docker` for test execution in docker build environment

* Fix too greedy router expression

* Add pmtile support

Co-authored-by: Andrew Calcutt <acalcutt@techidiots.net>

* add encoding param to pmtile section

* add map controls

Co-authored-by: Andrew Calcutt <acalcutt@techidiots.net>

* remove not needed check

* fix possible float usage in thumbnail url

* update readme for encoding option

* add better link name

---------

Co-authored-by: Miko <miko@none>
Co-authored-by: Andrew Calcutt <acalcutt@techidiots.net>

docs/config.rst

@@ -238,9 +238,26 @@ For example::
     }
   }
 
-
 The data source does not need to be specified here unless you explicitly want to serve the raw data.
 
+Serving Terrain Tiles
+--------------
+
+If you serve terrain tiles, it is possible to configure an ``encoding`` with ``mapbox`` or ``terrarium`` to enable a terrain preview mode and the ``elevation`` api for the ``data`` endpoint.
+
+For example::
+
+  "data": {
+    "terrain1": {
+      "mbtiles": "terrain1.mbtiles",
+      "encoding": "mapbox"
+    },
+    "terrain2": {
+      "pmtiles": "terrain2.pmtiles"
+      "encoding": "terrarium"
+    }
+  }
+
 Referencing local files from style JSON
 =======================================
 
@@ -283,7 +300,7 @@ For example::
     "source3": {
       "url": "pmtiles://https://foo.lan/source3.pmtiles",
       "type": "vector"
-    },
+    }
   }
 
 Alternatively, you can use ``pmtiles://{source2}`` to reference existing data object from the config.

docs/endpoints.rst

@@ -100,6 +100,14 @@ Source data
 
   * TileJSON at ``/data/{id}.json``
 
+  * If terrain mbtile data is served and ``encoding`` is configured (see config) the elevation can be queried 
+
+    * by ``/data/{id}/elevation/{z}/{x}/{y}`` for the tile
+
+    * or ``/data/{id}/elevation/{z}/{long}/{lat}`` for the coordinate
+
+    * the result will be a json object like ``{"z":7,"x":68,"y":45,"red":134,"green":66,"blue":0,"latitude":11.84069,"longitude":46.04798,"elevation":1602}``
+
 Static files
 ===========
 * Static files are served at ``/files/{filename}``

package.json

@@ -7,6 +7,7 @@
   "type": "module",
   "scripts": {
     "test": "mocha test/**.js --timeout 10000 --exit",
+    "test-docker": "xvfb-run npm test",
     "lint:yml": "yamllint --schema=CORE_SCHEMA *.{yml,yaml}",
     "lint:js": "npm run lint:eslint && npm run lint:prettier",
     "lint:js:fix": "npm run lint:eslint:fix && npm run lint:prettier:fix",

public/resources/index.css

@@ -114,7 +114,7 @@ section {
 }
 .details h3 {
   font-size: 18px;
-  margin-top: 25px;
+  margin-top: 5px;
 }
 .details p {
   padding: 0;

public/templates/data.tmpl

@@ -4,20 +4,25 @@
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>{{name}} - TileServer GL</title>
-  {{#is_vector}}
+  {{#use_maplibre}}
   <link rel="stylesheet" type="text/css" href="{{public_url}}maplibre-gl.css{{&key_query}}" />
   <link rel="stylesheet" type="text/css" href="{{public_url}}maplibre-gl-inspect.css{{&key_query}}" />
   <script src="{{public_url}}maplibre-gl.js{{&key_query}}"></script>
   <script src="{{public_url}}maplibre-gl-inspect.js{{&key_query}}"></script>
   <style>
     body {background:#fff;color:#333;font-family:Arial, sans-serif;}
+    {{^is_terrain}}
     #map {position:absolute;top:0;left:0;right:250px;bottom:0;}
+    {{/is_terrain}}
+    {{#is_terrain}}
+    #map { position:absolute; top:0; bottom:0; width:100%; }
+    {{/is_terrain}}
     h1 {position:absolute;top:5px;right:0;width:240px;margin:0;line-height:20px;font-size:20px;}
     #layerList {position:absolute;top:35px;right:0;bottom:0;width:240px;overflow:auto;}
     #layerList div div {width:15px;height:15px;display:inline-block;}
   </style>
-  {{/is_vector}}
+  {{/use_maplibre}}
-  {{^is_vector}}
+  {{^use_maplibre}}
   <link rel="stylesheet" type="text/css" href="{{public_url}}leaflet.css{{&key_query}}" />
   <script src="{{public_url}}leaflet.js{{&key_query}}"></script>
   <script src="{{public_url}}leaflet-hash.js{{&key_query}}"></script>
@@ -37,23 +42,22 @@
       background-image: url({{public_url}}images/marker-icon.png{{&key_query}});
     }
   </style>
-  {{/is_vector}}
+  {{/use_maplibre}}
 </head>
 <body>
-  {{#is_vector}}
+  {{#use_maplibre}}
   <h1>{{name}}</h1>
   <div id="map"></div>
+  {{^is_terrain}}
   <div id="layerList"></div>
   <pre id="propertyList"></pre>
+  {{/is_terrain}}
   <script>
     var keyMatch = location.search.match(/[\?\&]key=([^&]+)/i);
     var keyParam = keyMatch ? '?key=' + keyMatch[1] : '';
 
-  var map = new maplibregl.Map({
+    {{^is_terrain}}
-    container: 'map',
+    var style = {
-    hash: true,
-    maxPitch: 85,
-    style: {
       version: 8,
       sources: {
         'vector_layer_': {
@@ -62,9 +66,71 @@
         }
       },
       layers: []
+    };
+    {{/is_terrain}}
+    {{#is_terrain}}
+    var style = {
+      version: 8,
+      sources: {
+        "terrain": {
+          "type": "raster-dem",
+          "url": "{{public_url}}data/{{id}}.json",
+          "encoding": "{{terrain_encoding}}"
+        },
+        "hillshade": {
+          "type": "raster-dem",
+          "url": "{{public_url}}data/{{id}}.json",
+          "encoding": "{{terrain_encoding}}"
         }
+      },
+      "terrain": {
+        "source": "terrain"
+      },
+      layers: [
+        {
+          "id": "background",
+          "paint": {
+            {{^if is_terrainrgb}}
+            "background-color": "hsl(190, 99%, 63%)"
+            {{else}}
+            "background-color": "hsl(0, 100%, 25%)"
+            {{/if}}
+          },
+          "type": "background"
+        },
+        {
+          "id": "hillshade",
+          "source": "hillshade",
+          "type": "hillshade",
+          "paint": {
+            "hillshade-shadow-color": "hsl(39, 21%, 33%)",
+            "hillshade-illumination-direction": 315,
+            "hillshade-exaggeration": 0.8
+          }
+        }
+      ]
+    };
+    {{/is_terrain}}
+
+    var map = new maplibregl.Map({
+      container: 'map',
+      hash: true,
+      maxPitch: 85,
+      style: style
     });
-  map.addControl(new maplibregl.NavigationControl());
+    map.addControl(new maplibregl.NavigationControl({
+      visualizePitch: true,
+      showZoom: true,
+      showCompass: true
+    }));
+    {{#is_terrain}}
+    map.addControl(
+      new maplibregl.TerrainControl({
+        source: "terrain",
+      })
+    );
+    {{/is_terrain}}
+    {{^is_terrain}}
     var inspect = new MaplibreInspect({
       showInspectMap: true,
       showInspectButton: false
@@ -84,15 +150,15 @@
         });
       })
     });
+    {{/is_terrain}}
   </script>
-  {{/is_vector}}
+  {{/use_maplibre}}
-  {{^is_vector}}
+  {{^use_maplibre}}
   <h1 style="display:none;">{{name}}</h1>
   <div id='map'></div>
   <script>
     var keyMatch = location.search.match(/[\?\&]key=([^&]+)/i);
     var keyParam = keyMatch ? '?key=' + keyMatch[1] : '';
-    
     var map = L.map('map', { zoomControl: false });
     new L.Control.Zoom({ position: 'topright' }).addTo(map);
 
@@ -141,6 +207,6 @@
       new L.Hash(map);
     }, 0);
   </script>
-  {{/is_vector}}
+  {{/use_maplibre}}
 </body>
 </html>

public/templates/index.tmpl

@@ -6,10 +6,15 @@
   <title>TileServer GL - Server for vector and raster maps with GL styles</title>
   <link rel="stylesheet" type="text/css" href="{{public_url}}index.css{{&key_query}}" />
   <script>
-    function toggle_xyz(id) {
+    function toggle_link(id, link) {
       var el = document.getElementById(id);
       var s = el.style;
-      s.display = s.display == 'none' ? 'inline-block' : 'none';
+      if (s.display == 'none') {
+        s.display = 'inline-block';
+      } else if (el.value == link) {
+        s.display = 'none';
+      }
+      el.value = link;
       el.setSelectionRange(0, el.value.length);
       return false;
     }
@@ -37,7 +42,7 @@
         <div class="filter-details">
           <h3>Filter styles and data by name or identifier</h3>
           <!-- filter input , needs to call filter() when content changes...-->
-          <input id="filter" type="text" oninput="filter()" placeholder="Start typing name or identifier" />
+          <input id="filter" type="text" oninput="filter()" placeholder="Start typing name or identifier" autofocus />
         </div>
       </div>
     </div>
@@ -66,8 +71,8 @@
                 | <a href="{{public_url}}styles/{{@key}}/wmts.xml{{&../key_query}}">WMTS</a>
               {{/if}}
               {{#if xyz_link}}
-                | <a href="#" onclick="return toggle_xyz('xyz_style_{{@key}}');">XYZ</a>
+                | <a href="#" onclick="return toggle_link('xyz_style_{{@key}}', '{{&xyz_link}}');">XYZ</a>
-                  <input id="xyz_style_{{@key}}" type="text" value="{{&xyz_link}}" style="display:none;" />
+                  <input id="xyz_style_{{@key}}" type="text" value="" style="display:none;" />
               {{/if}}
             </p>
           </div>
@@ -105,9 +110,12 @@
             <p class="services">
               services: <a href="{{public_url}}data/{{@key}}.json{{&../key_query}}">TileJSON</a>
               {{#if xyz_link}}
-                | <a href="#" onclick="return toggle_xyz('xyz_data_{{@key}}');">XYZ</a>
+                | <a href="#" onclick="return toggle_link('link_data_{{@key}}', '{{&xyz_link}}');">XYZ</a>
-                  <input id="xyz_data_{{@key}}" type="text" value="{{&xyz_link}}" style="display:none;" />
               {{/if}}
+              {{#if elevation_link}}
+                | <a href="#" onclick="return toggle_link('link_data_{{@key}}', '{{&elevation_link}}');">Elevation</a>
+              {{/if}}
+                <input id="link_data_{{@key}}" type="text" value="" style="display:none;" />
             </p>
           </div>
           <div class="viewers">
@@ -116,6 +124,9 @@
             {{/is_vector}}
             {{^is_vector}}
             <a class="btn" href="{{public_url}}data/{{@key}}/{{&../key_query}}{{viewer_hash}}">View</a>
+              {{#elevation_link}}
+            <a class="btn" href="{{public_url}}data/preview/{{@key}}/{{&../key_query}}{{viewer_hash}}">Preview Terrain</a>
+              {{/elevation_link}}
             {{/is_vector}}
           </div>
         </div>

src/serve_data.js

@@ -7,6 +7,9 @@ import clone from 'clone';
 import express from 'express';
 import Pbf from 'pbf';
 import { VectorTile } from '@mapbox/vector-tile';
+import SphericalMercator from '@mapbox/sphericalmercator';
+import { Image, createCanvas } from 'canvas';
+import sharp from 'sharp';
 
 import { fixTileJSONCenter, getTileUrls, isValidHttpUrl } from './utils.js';
 import {
@@ -162,6 +165,183 @@ export const serve_data = {
       },
     );
 
+    app.get(
+      '^/:id/elevation/:z([0-9]+)/:x([-.0-9]+)/:y([-.0-9]+)',
+      async (req, res, next) => {
+        try {
+          const item = repo?.[req.params.id];
+          if (!item) return res.sendStatus(404);
+          if (!item.source) return res.status(404).send('Missing source');
+          if (!item.tileJSON) return res.status(404).send('Missing tileJSON');
+          if (!item.sourceType)
+            return res.status(404).send('Missing sourceType');
+
+          const { source, tileJSON, sourceType } = item;
+
+          if (sourceType !== 'pmtiles' && sourceType !== 'mbtiles') {
+            return res
+              .status(400)
+              .send('Invalid sourceType. Must be pmtiles or mbtiles.');
+          }
+
+          const encoding = tileJSON?.encoding;
+          if (encoding == null) {
+            return res.status(400).send('Missing tileJSON.encoding');
+          } else if (encoding !== 'terrarium' && encoding !== 'mapbox') {
+            return res
+              .status(400)
+              .send('Invalid encoding. Must be terrarium or mapbox.');
+          }
+
+          const format = tileJSON?.format;
+          if (format == null) {
+            return res.status(400).send('Missing tileJSON.format');
+          } else if (format !== 'webp' && format !== 'png') {
+            return res.status(400).send('Invalid format. Must be webp or png.');
+          }
+
+          const z = parseInt(req.params.z, 10);
+          const x = parseFloat(req.params.x);
+          const y = parseFloat(req.params.y);
+
+          if (tileJSON.minzoom == null || tileJSON.maxzoom == null) {
+            return res.status(404).send(JSON.stringify(tileJSON));
+          }
+
+          const TILE_SIZE = 256;
+          let tileCenter;
+          let xy;
+
+          if (Number.isInteger(x) && Number.isInteger(y)) {
+            const intX = parseInt(req.params.x, 10);
+            const intY = parseInt(req.params.y, 10);
+
+            if (
+              z < tileJSON.minzoom ||
+              z > tileJSON.maxzoom ||
+              intX < 0 ||
+              intY < 0 ||
+              intX >= Math.pow(2, z) ||
+              intY >= Math.pow(2, z)
+            ) {
+              return res.status(404).send('Out of bounds');
+            }
+            xy = [intX, intY];
+            tileCenter = new SphericalMercator().bbox(intX, intY, z);
+          } else {
+            if (
+              z < tileJSON.minzoom ||
+              z > tileJSON.maxzoom ||
+              x < -180 ||
+              y < -90 ||
+              x > 180 ||
+              y > 90
+            ) {
+              return res.status(404).send('Out of bounds');
+            }
+
+            tileCenter = [y, x, y + 0.1, x + 0.1];
+            const { minX, minY } = new SphericalMercator().xyz(tileCenter, z);
+            xy = [minX, minY];
+          }
+
+          let data;
+          if (sourceType === 'pmtiles') {
+            const tileinfo = await getPMtilesTile(source, z, x, y);
+            if (!tileinfo?.data) return res.status(204).send();
+            data = tileinfo.data;
+          } else {
+            data = await new Promise((resolve, reject) => {
+              source.getTile(z, xy[0], xy[1], (err, tileData) => {
+                if (err) {
+                  return /does not exist/.test(err.message)
+                    ? resolve(null)
+                    : reject(err);
+                }
+                resolve(tileData);
+              });
+            });
+          }
+          if (data == null) return res.status(204).send();
+          if (!data) return res.status(404).send('Not found');
+
+          const image = new Image();
+          await new Promise(async (resolve, reject) => {
+            image.onload = async () => {
+              const canvas = createCanvas(TILE_SIZE, TILE_SIZE);
+              const context = canvas.getContext('2d');
+              context.drawImage(image, 0, 0);
+              const imgdata = context.getImageData(0, 0, TILE_SIZE, TILE_SIZE);
+
+              const arrayWidth = imgdata.width;
+              const arrayHeight = imgdata.height;
+              const bytesPerPixel = 4;
+
+              const xPixel = Math.floor(xy[0]);
+              const yPixel = Math.floor(xy[1]);
+
+              if (
+                xPixel < 0 ||
+                yPixel < 0 ||
+                xPixel >= arrayWidth ||
+                yPixel >= arrayHeight
+              ) {
+                return reject('Out of bounds Pixel');
+              }
+
+              const index = (yPixel * arrayWidth + xPixel) * bytesPerPixel;
+
+              const red = imgdata.data[index];
+              const green = imgdata.data[index + 1];
+              const blue = imgdata.data[index + 2];
+
+              let elevation;
+              if (encoding === 'mapbox') {
+                elevation =
+                  -10000 + (red * 256 * 256 + green * 256 + blue) * 0.1;
+              } else if (encoding === 'terrarium') {
+                elevation = red * 256 + green + blue / 256 - 32768;
+              } else {
+                elevation = 'invalid encoding';
+              }
+
+              resolve(
+                res.status(200).send({
+                  z,
+                  x: xy[0],
+                  y: xy[1],
+                  red,
+                  green,
+                  blue,
+                  latitude: tileCenter[0],
+                  longitude: tileCenter[1],
+                  elevation,
+                }),
+              );
+            };
+
+            image.onerror = (err) => reject(err);
+
+            if (format === 'webp') {
+              try {
+                const img = await sharp(data).toFormat('png').toBuffer();
+                image.src = img;
+              } catch (err) {
+                reject(err);
+              }
+            } else {
+              image.src = data;
+            }
+          });
+        } catch (err) {
+          return res
+            .status(500)
+            .header('Content-Type', 'text/plain')
+            .send(err.message);
+        }
+      },
+    );
+
     app.get('/:id.json', (req, res, next) => {
       const item = repo[req.params.id];
       if (!item) {
@@ -225,6 +405,7 @@ export const serve_data = {
       sourceType = 'pmtiles';
       const metadata = await getPMtilesInfo(source);
 
+      tileJSON['encoding'] = params['encoding'];
       tileJSON['name'] = id;
       tileJSON['format'] = 'pbf';
       Object.assign(tileJSON, metadata);
@@ -245,6 +426,7 @@ export const serve_data = {
       const mbw = await openMbTilesWrapper(inputFile);
       const info = await mbw.getInfo();
       source = mbw.getMbTiles();
+      tileJSON['encoding'] = params['encoding'];
       tileJSON['name'] = id;
       tileJSON['format'] = 'pbf';
 

src/server.js

@@ -468,7 +468,7 @@ function start(opts) {
 
           const centerPx = mercator.px([center[0], center[1]], center[2]);
           // Set thumbnail default size to be 256px x 256px
-          style.thumbnail = `${center[2]}/${Math.floor(centerPx[0] / 256)}/${Math.floor(centerPx[1] / 256)}.png`;
+          style.thumbnail = `${Math.floor(center[2])}/${Math.floor(centerPx[0] / 256)}/${Math.floor(centerPx[1] / 256)}.png`;
         }
 
         const tileSize = 512;
@@ -498,14 +498,6 @@ function start(opts) {
         )}/${center[0].toFixed(5)}`;
       }
 
-      data.is_vector = tileJSON.format === 'pbf';
-      if (!data.is_vector) {
-        if (center) {
-          const centerPx = mercator.px([center[0], center[1]], center[2]);
-          data.thumbnail = `${center[2]}/${Math.floor(centerPx[0] / 256)}/${Math.floor(centerPx[1] / 256)}.${tileJSON.format}`;
-        }
-      }
-
       const tileSize = undefined;
       data.xyz_link = getTileUrls(
         req,
@@ -519,6 +511,24 @@ function start(opts) {
         },
       )[0];
 
+      data.is_vector = tileJSON.format === 'pbf';
+      if (!data.is_vector) {
+        if (
+          tileJSON.encoding === 'terrarium' ||
+          tileJSON.encoding === 'mapbox'
+        ) {
+          data.elevation_link = getTileUrls(
+            req,
+            tileJSON.tiles,
+            `data/${id}/elevation`,
+          )[0];
+        }
+        if (center) {
+          const centerPx = mercator.px([center[0], center[1]], center[2]);
+          data.thumbnail = `${Math.floor(center[2])}/${Math.floor(centerPx[0] / 256)}/${Math.floor(centerPx[1] / 256)}.${tileJSON.format}`;
+        }
+      }
+
       if (data.filesize) {
         let suffix = 'kB';
         let size = parseInt(tileJSON.filesize, 10) / 1024;
@@ -595,18 +605,25 @@ function start(opts) {
     };
   });
 
-  serveTemplate('/data/:id/$', 'data', (req) => {
+  serveTemplate('^/data/(:preview(preview)/)?:id/$', 'data', (req) => {
-    const { id } = req.params;
+    const id = req.params.id;
+    const preview = req.params.preview || undefined;
     const data = serving.data[id];
 
     if (!data) {
       return null;
     }
-
+    const is_terrain =
+      (data.tileJSON.encoding === 'terrarium' ||
+        data.tileJSON.encoding === 'mapbox') &&
+      preview === 'preview';
     return {
       ...data,
       id,
-      is_vector: data.tileJSON.format === 'pbf',
+      use_maplibre: data.tileJSON.format === 'pbf' || is_terrain,
+      is_terrain: is_terrain,
+      is_terrainrgb: data.tileJSON.encoding === 'mapbox',
+      terrain_encoding: data.tileJSON.encoding,
     };
   });
 

src/utils.js

@@ -119,16 +119,22 @@ export const getTileUrls = (
     tileParams = `${tileSize}/{z}/{x}/{y}`;
   }
 
+  if (format && format != '') {
+    format = `.${format}`;
+  } else {
+    format = '';
+  }
+
   const uris = [];
   if (!publicUrl) {
     let xForwardedPath = `${req.get('X-Forwarded-Path') ? '/' + req.get('X-Forwarded-Path') : ''}`;
     for (const domain of domains) {
       uris.push(
-        `${req.protocol}://${domain}${xForwardedPath}/${path}/${tileParams}.${format}${query}`,
+        `${req.protocol}://${domain}${xForwardedPath}/${path}/${tileParams}${format}${query}`,
       );
     }
   } else {
-    uris.push(`${publicUrl}${path}/${tileParams}.${format}${query}`);
+    uris.push(`${publicUrl}${path}/${tileParams}${format}${query}`);
   }
 
   return uris;