Rendering raster tiles with WebGL

examples/cog-math.html

@@ -0,0 +1,11 @@
+---
+layout: example.html
+title: NDVI from a Sentinel 2 COG
+shortdesc: Calculating NDVI and applying a custom color map.
+docs: >
+  The GeoTIFF layer in this example draws from two Sentinel 2 sources: a red band and a near infrared band.
+  The layer style includes a `color` expression that calculates the Normalized Difference Vegetation Index (NDVI)
+  from values in the two bands.  The `interpolate` expression is used to map NDVI values to colors.
+tags: "cog, ndvi"
+---
+<div id="map" class="map"></div>

examples/cog-math.js

@@ -0,0 +1,105 @@
+import GeoTIFF from '../src/ol/source/GeoTIFF.js';
+import Map from '../src/ol/Map.js';
+import Projection from '../src/ol/proj/Projection.js';
+import TileLayer from '../src/ol/layer/WebGLTile.js';
+import View from '../src/ol/View.js';
+import proj4 from 'proj4';
+import {getCenter} from '../src/ol/extent.js';
+import {register} from '../src/ol/proj/proj4.js';
+
+proj4.defs('EPSG:32636', '+proj=utm +zone=36 +datum=WGS84 +units=m +no_defs');
+register(proj4);
+
+const projection = new Projection({
+  code: 'EPSG:32636',
+  extent: [166021.44, 0.0, 534994.66, 9329005.18],
+});
+
+// metadata from https://s3.us-west-2.amazonaws.com/sentinel-cogs/sentinel-s2-l2a-cogs/2020/S2A_36QWD_20200701_0_L2A/S2A_36QWD_20200701_0_L2A.json
+const sourceExtent = [499980, 1790220, 609780, 1900020];
+
+const map = new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      style: {
+        color: [
+          'interpolate',
+          ['linear'],
+          // calculate NDVI, bands come from the sources below
+          [
+            '/',
+            ['-', ['band', 2], ['band', 1]],
+            ['+', ['band', 2], ['band', 1]],
+          ],
+          // color ramp for NDVI values, ranging from -1 to 1
+          -0.2,
+          [191, 191, 191],
+          -0.1,
+          [219, 219, 219],
+          0,
+          [255, 255, 224],
+          0.025,
+          [255, 250, 204],
+          0.05,
+          [237, 232, 181],
+          0.075,
+          [222, 217, 156],
+          0.1,
+          [204, 199, 130],
+          0.125,
+          [189, 184, 107],
+          0.15,
+          [176, 194, 97],
+          0.175,
+          [163, 204, 89],
+          0.2,
+          [145, 191, 82],
+          0.25,
+          [128, 179, 71],
+          0.3,
+          [112, 163, 64],
+          0.35,
+          [97, 150, 54],
+          0.4,
+          [79, 138, 46],
+          0.45,
+          [64, 125, 36],
+          0.5,
+          [48, 110, 28],
+          0.55,
+          [33, 97, 18],
+          0.6,
+          [15, 84, 10],
+          0.65,
+          [0, 69, 0],
+        ],
+      },
+      source: new GeoTIFF({
+        sources: [
+          {
+            // visible red, band 1 in the style expression above
+            url:
+              'https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/2020/S2A_36QWD_20200701_0_L2A/B04.tif',
+            nodata: 0,
+            max: 10000,
+          },
+          {
+            // near infrared, band 2 in the style expression above
+            url:
+              'https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/2020/S2A_36QWD_20200701_0_L2A/B08.tif',
+            nodata: 0,
+            max: 10000,
+          },
+        ],
+      }),
+      extent: sourceExtent,
+    }),
+  ],
+  view: new View({
+    center: getCenter(sourceExtent),
+    extent: sourceExtent,
+    zoom: 9,
+    projection: projection,
+  }),
+});

examples/cog-overviews.html

@@ -0,0 +1,12 @@
+---
+layout: example.html
+title: GeoTIFF with Overviews
+shortdesc: Rendering a GeoTIFF with external overviews as a layer.
+docs: >
+  In some cases, a GeoTIFF may have external overviews.  This example uses the
+  `overviews` property to provide URLs for the external overviews.  The example
+  composes a false color composite using shortwave infrared (B6), near infrared (B5),
+  and visible green (B3) bands from a Landsat 8 image.
+tags: "cog"
+---
+<div id="map" class="map"></div>

examples/cog-overviews.js

@@ -0,0 +1,68 @@
+import GeoTIFF from '../src/ol/source/GeoTIFF.js';
+import Map from '../src/ol/Map.js';
+import Projection from '../src/ol/proj/Projection.js';
+import TileLayer from '../src/ol/layer/WebGLTile.js';
+import View from '../src/ol/View.js';
+import proj4 from 'proj4';
+import {getCenter} from '../src/ol/extent.js';
+import {register} from '../src/ol/proj/proj4.js';
+
+proj4.defs('EPSG:32645', '+proj=utm +zone=45 +datum=WGS84 +units=m +no_defs');
+register(proj4);
+
+const projection = new Projection({
+  code: 'EPSG:32645',
+  extent: [166021.44, 0.0, 534994.66, 9329005.18],
+});
+
+const sourceExtent = [382200, 2279370, 610530, 2512500];
+
+const base =
+  'https://landsat-pds.s3.amazonaws.com/c1/L8/139/045/LC08_L1TP_139045_20170304_20170316_01_T1/LC08_L1TP_139045_20170304_20170316_01_T1';
+
+// scale values in this range to 0 - 1
+const min = 10000;
+const max = 15000;
+
+const map = new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      extent: sourceExtent,
+      style: {
+        saturation: -0.3,
+      },
+      source: new GeoTIFF({
+        sources: [
+          {
+            url: `${base}_B6.TIF`,
+            overviews: [`${base}_B6.TIF.ovr`],
+            min: min,
+            max: max,
+            nodata: 0,
+          },
+          {
+            url: `${base}_B5.TIF`,
+            overviews: [`${base}_B5.TIF.ovr`],
+            min: min,
+            max: max,
+            nodata: 0,
+          },
+          {
+            url: `${base}_B3.TIF`,
+            overviews: [`${base}_B3.TIF.ovr`],
+            min: min,
+            max: max,
+            nodata: 0,
+          },
+        ],
+      }),
+    }),
+  ],
+  view: new View({
+    center: getCenter(sourceExtent),
+    extent: sourceExtent,
+    zoom: 8,
+    projection: projection,
+  }),
+});

examples/cog.html

@@ -0,0 +1,11 @@
+---
+layout: example.html
+title: Cloud Optimized GeoTIFF (COG)
+shortdesc: Rendering a COG as a tiled layer.
+docs: >
+  Tiled data from a Cloud Optimized GeoTIFF (COG) can be rendered as a layer.  In this
+  example, a single 3-band GeoTIFF is used to render RGB data.  The `nodata` property is
+  used to avoid rendering pixels where all three bands are 0.
+tags: "cog"
+---
+<div id="map" class="map"></div>

examples/cog.js

@@ -0,0 +1,43 @@
+import GeoTIFF from '../src/ol/source/GeoTIFF.js';
+import Map from '../src/ol/Map.js';
+import Projection from '../src/ol/proj/Projection.js';
+import TileLayer from '../src/ol/layer/WebGLTile.js';
+import View from '../src/ol/View.js';
+import proj4 from 'proj4';
+import {getCenter} from '../src/ol/extent.js';
+import {register} from '../src/ol/proj/proj4.js';
+
+proj4.defs('EPSG:32636', '+proj=utm +zone=36 +datum=WGS84 +units=m +no_defs');
+register(proj4);
+
+const projection = new Projection({
+  code: 'EPSG:32636',
+  extent: [166021.44, 0.0, 534994.66, 9329005.18],
+});
+
+// metadata from https://s3.us-west-2.amazonaws.com/sentinel-cogs/sentinel-s2-l2a-cogs/2020/S2A_36QWD_20200701_0_L2A/S2A_36QWD_20200701_0_L2A.json
+const sourceExtent = [499980, 1790220, 609780, 1900020];
+
+const map = new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      source: new GeoTIFF({
+        sources: [
+          {
+            url:
+              'https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/2020/S2A_36QWD_20200701_0_L2A/TCI.tif',
+            nodata: 0,
+          },
+        ],
+      }),
+      extent: sourceExtent,
+    }),
+  ],
+  view: new View({
+    center: getCenter(sourceExtent),
+    extent: sourceExtent,
+    zoom: 9,
+    projection: projection,
+  }),
+});

examples/data-tiles.html

@@ -0,0 +1,9 @@
+---
+layout: example.html
+title: Data Tiles
+shortdesc: Generating tile data from scratch.
+docs: >
+  This example generates RGBA tile data from scratch.
+tags: "data tiles"
+---
+<div id="map" class="map"></div>

examples/data-tiles.js

@@ -0,0 +1,43 @@
+import DataTile from '../src/ol/source/DataTile.js';
+import Map from '../src/ol/Map.js';
+import TileLayer from '../src/ol/layer/WebGLTile.js';
+import View from '../src/ol/View.js';
+
+const size = 256;
+
+const canvas = document.createElement('canvas');
+canvas.width = size;
+canvas.height = size;
+
+const context = canvas.getContext('2d');
+context.strokeStyle = 'white';
+context.textAlign = 'center';
+context.font = '24px sans-serif';
+const lineHeight = 30;
+
+const map = new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      source: new DataTile({
+        loader: function (z, x, y) {
+          const half = size / 2;
+          context.clearRect(0, 0, size, size);
+          context.fillStyle = 'rgba(100, 100, 100, 0.5)';
+          context.fillRect(0, 0, size, size);
+          context.fillStyle = 'black';
+          context.fillText(`z: ${z}`, half, half - lineHeight);
+          context.fillText(`x: ${x}`, half, half);
+          context.fillText(`y: ${y}`, half, half + lineHeight);
+          context.strokeRect(0, 0, size, size);
+          const data = context.getImageData(0, 0, size, size).data;
+          return Promise.resolve(data);
+        },
+      }),
+    }),
+  ],
+  view: new View({
+    center: [0, 0],
+    zoom: 0,
+  }),
+});

examples/webgl-sea-level.css

@@ -0,0 +1,13 @@
+#level {
+  display: inline-block;
+  width: 150px;
+  vertical-align: text-bottom;
+}
+
+a.location {
+  cursor: pointer;
+}
+
+#map {
+  background: #8bd4ff;
+}

examples/webgl-sea-level.html

@@ -0,0 +1,37 @@
+---
+layout: example.html
+title: Sea Level (with WebGL)
+shortdesc: Render sea level at different elevations
+docs: >
+  <p>
+    The <code>style</code> property of a WebGL tile layer accepts a <code>color</code> expression that
+    can be used to modify pixel values before rendering.  Here, RGB tiles representing elevation
+    data are loaded and rendered so that values at or below sea level are blue, and values
+    above sea level are transparent.  The <code>color</code> expression operates on normalized pixel
+    values ranging from 0 to 1.  The <code>band</code> operator is used to select normalized values
+    from a single band.
+  </p><p>
+    After converting the normalized RGB values to elevation, the <code>interpolate</code> expression
+    is used to pick colors to apply at a given elevation.  Instead of using constant
+    numeric values as the stops in the colors array, the <code>var</code> operator allows you to
+    use a value that can be modified by your application.  When the user drags the
+    sea level slider, the <code>layer.updateStyleVariables()</code> function is called to update
+    the <code>level</code> style variable with the value from the slider.
+  </p>
+tags: "webgl, math, flood"
+cloak:
+  - key: get_your_own_D6rA4zTHduk6KOKTXzGB
+    value: Get your own API key at https://www.maptiler.com/cloud/
+---
+<div id="map" class="map"></div>
+<label>
+  Sea level
+  <input id="level" type="range" min="0" max="100" value="1"/>
+  +<span id="output"></span> m
+</label>
+<br>
+Go to
+<a class="location" data-center="-122.3267,37.8377" data-zoom="11">San Francisco</a>,
+<a class="location" data-center="-73.9338,40.6861" data-zoom="11">New York</a>,
+<a class="location" data-center="72.9481,18.9929" data-zoom="11">Mumbai</a>, or
+<a class="location" data-center="120.831,31.160" data-zoom="9">Shanghai</a>

examples/webgl-sea-level.js

@@ -0,0 +1,90 @@
+import Map from '../src/ol/Map.js';
+import TileLayer from '../src/ol/layer/WebGLTile.js';
+import View from '../src/ol/View.js';
+import XYZ from '../src/ol/source/XYZ.js';
+import {fromLonLat} from '../src/ol/proj.js';
+
+const key = 'get_your_own_D6rA4zTHduk6KOKTXzGB';
+const attributions =
+  '<a href="https://www.maptiler.com/copyright/" target="_blank">&copy; MapTiler</a> ' +
+  '<a href="https://www.openstreetmap.org/copyright" target="_blank">&copy; OpenStreetMap contributors</a>';
+
+const elevation = new TileLayer({
+  opacity: 0.6,
+  source: new XYZ({
+    url:
+      'https://api.maptiler.com/tiles/terrain-rgb/{z}/{x}/{y}.png?key=' + key,
+    maxZoom: 10,
+    tileSize: 512,
+    crossOrigin: 'anonymous',
+  }),
+  style: {
+    variables: {
+      level: 0,
+    },
+    color: [
+      'interpolate',
+      ['linear'],
+      // band math operates on normalized values from 0-1
+      // so we scale by 255 to align with the elevation formula
+      // from https://cloud.maptiler.com/tiles/terrain-rgb/
+      [
+        '+',
+        -10000,
+        [
+          '*',
+          0.1 * 255,
+          [
+            '+',
+            ['*', 256 * 256, ['band', 1]],
+            ['+', ['*', 256, ['band', 2]], ['band', 3]],
+          ],
+        ],
+      ],
+      // use the `level` style variable as a stop in the color ramp
+      ['var', 'level'],
+      [139, 212, 255, 1],
+      ['+', 0.01, ['var', 'level']],
+      [139, 212, 255, 0],
+    ],
+  },
+});
+
+const map = new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      source: new XYZ({
+        url: 'https://api.maptiler.com/maps/streets/{z}/{x}/{y}.png?key=' + key,
+        attributions: attributions,
+        crossOrigin: 'anonymous',
+        tileSize: 512,
+      }),
+    }),
+    elevation,
+  ],
+  view: new View({
+    center: fromLonLat([-122.3267, 37.8377]),
+    zoom: 11,
+  }),
+});
+
+const control = document.getElementById('level');
+const output = document.getElementById('output');
+control.addEventListener('input', function () {
+  output.innerText = control.value;
+  elevation.updateStyleVariables({level: parseFloat(control.value)});
+});
+output.innerText = control.value;
+
+const locations = document.getElementsByClassName('location');
+for (let i = 0, ii = locations.length; i < ii; ++i) {
+  locations[i].addEventListener('click', relocate);
+}
+
+function relocate(event) {
+  const data = event.target.dataset;
+  const view = map.getView();
+  view.setCenter(fromLonLat(data.center.split(',').map(Number)));
+  view.setZoom(Number(data.zoom));
+}

examples/webgl-tile-style.css

@@ -0,0 +1,4 @@
+#controls {
+  display: flex;
+  justify-content: space-around;
+}

examples/webgl-tile-style.html

@@ -0,0 +1,31 @@
+---
+layout: example.html
+title: WebGL Tile Layer Styles
+shortdesc: Styling raster tiles with WebGL.
+docs: >
+  The `style` property of a WebGL tile layer can be used to adjust properties like
+  `exposure`, `contrast`, and `saturation`.  Typically those values would be set to
+  numeric constants to apply a filter to imagery.  In this example, the style properties
+  are set to variables that can be updated based on application state.  Adjusting the
+  sliders results in a call to `layer.updateStyleVariables()` to use new values for the
+  associated style properties.
+tags: "webgl, style"
+cloak:
+  - key: get_your_own_D6rA4zTHduk6KOKTXzGB
+    value: Get your own API key at https://www.maptiler.com/cloud/
+---
+<div id="map" class="map"></div>
+<div id="controls">
+  <label>
+    <input id="exposure" type="range" min="-0.5" max="0.5" step="0.01">
+    <br>exposure <span id="exposure-value"></span>
+  </label>
+  <label>
+    <input id="contrast" type="range" min="-0.5" max="0.5" step="0.01">
+    <br>contrast <span id="contrast-value"></span>
+  </label>
+  <label>
+    <input id="saturation" type="range" min="-0.5" max="0.5" step="0.01">
+    <br>saturation <span id="saturation-value"></span>
+  </label>
+</div>

examples/webgl-tile-style.js

@@ -0,0 +1,55 @@
+import Map from '../src/ol/Map.js';
+import TileLayer from '../src/ol/layer/WebGLTile.js';
+import View from '../src/ol/View.js';
+import XYZ from '../src/ol/source/XYZ.js';
+
+const key = 'get_your_own_D6rA4zTHduk6KOKTXzGB';
+const attributions =
+  '<a href="https://www.maptiler.com/copyright/" target="_blank">&copy; MapTiler</a> ' +
+  '<a href="https://www.openstreetmap.org/copyright" target="_blank">&copy; OpenStreetMap contributors</a>';
+
+const variables = {
+  exposure: 0,
+  contrast: 0,
+  saturation: 0,
+};
+
+const layer = new TileLayer({
+  style: {
+    exposure: ['var', 'exposure'],
+    contrast: ['var', 'contrast'],
+    saturation: ['var', 'saturation'],
+    variables: variables,
+  },
+  source: new XYZ({
+    crossOrigin: 'anonymous', // TODO: determine if we can avoid this
+    attributions: attributions,
+    url: 'https://api.maptiler.com/tiles/satellite/{z}/{x}/{y}.jpg?key=' + key,
+    maxZoom: 20,
+  }),
+});
+
+const map = new Map({
+  target: 'map',
+  layers: [layer],
+  view: new View({
+    center: [0, 0],
+    zoom: 0,
+  }),
+});
+
+for (const name in variables) {
+  const element = document.getElementById(name);
+  const value = variables[name];
+  element.value = value.toString();
+  document.getElementById(`${name}-value`).innerText = `(${value})`;
+
+  element.addEventListener('input', function (event) {
+    const value = parseFloat(event.target.value);
+    document.getElementById(`${name}-value`).innerText = `(${value})`;
+
+    const updates = {};
+    updates[name] = value;
+    layer.updateStyleVariables(updates);
+  });
+}

examples/webgl-tiles.html

@@ -0,0 +1,9 @@
+---
+layout: example.html
+title: WebGL Tiles
+shortdesc: Rendering raster data with WebGL.
+docs: >
+  This example uses WebGL to raster tiles on a map.
+tags: "webgl, osm"
+---
+<div id="map" class="map"></div>

examples/webgl-tiles.js

@@ -0,0 +1,17 @@
+import Map from '../src/ol/Map.js';
+import OSM from '../src/ol/source/OSM.js';
+import TileLayer from '../src/ol/layer/WebGLTile.js';
+import View from '../src/ol/View.js';
+
+const map = new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      source: new OSM(),
+    }),
+  ],
+  view: new View({
+    center: [0, 0],
+    zoom: 0,
+  }),
+});

examples/webpack/config.mjs

@@ -101,6 +101,8 @@ export default {
   resolve: {
     fallback: {
       fs: false,
+      http: false,
+      https: false,
     },
     alias: {
       // allow imports from 'ol/module' instead of specifiying the source path

package-lock.json

@@ -9,6 +9,7 @@
       "version": "6.6.2-dev",
       "license": "BSD-2-Clause",
       "dependencies": {
+        "geotiff": "^1.0.0-beta.16",
         "ol-mapbox-style": "^6.4.1",
         "pbf": "3.2.1",
         "rbush": "^3.0.1"
@@ -1837,6 +1838,15 @@
         "eslint": ">=5.1.0"
       }
     },
+    "node_modules/@petamoriken/float16": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/@petamoriken/float16/-/float16-1.1.1.tgz",
+      "integrity": "sha512-0r8nE5Q60tj3FbWWYLjAdGnWZgP7CMWXNaI5UsNzypRyxLDb/uvOl5SDw8GcPNu6pSTOt+KSI+0oL6fhSpNOFQ==",
+      "dependencies": {
+        "lodash": ">=4.17.5 <5.0.0",
+        "lodash-es": ">=4.17.5 <5.0.0"
+      }
+    },
     "node_modules/@rollup/plugin-babel": {
       "version": "5.3.0",
       "resolved": "https://registry.npmjs.org/@rollup/plugin-babel/-/plugin-babel-5.3.0.tgz",
@@ -2968,7 +2978,6 @@
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/callsites/-/callsites-3.1.0.tgz",
       "integrity": "sha512-P8BjAsXvZS+VIDUI11hHCQEv74YT67YUi5JJFNWIqL235sBmjX4+qx9Muvls5ivyNENctx46xQLQ3aTuE7ssaQ==",
-      "dev": true,
       "engines": {
         "node": ">=6"
       }
@@ -3336,6 +3345,11 @@
         "node": ">= 0.6"
       }
     },
+    "node_modules/content-type-parser": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/content-type-parser/-/content-type-parser-1.0.2.tgz",
+      "integrity": "sha512-lM4l4CnMEwOLHAHr/P6MEZwZFPJFtAAKgL6pogbXmVZggIqXhdB6RbBtPOTsw2FcXwYhehRGERJmRrjOiIB8pQ=="
+    },
     "node_modules/convert-source-map": {
       "version": "1.7.0",
       "resolved": "https://registry.npmjs.org/convert-source-map/-/convert-source-map-1.7.0.tgz",
@@ -3576,7 +3590,6 @@
       "version": "4.3.1",
       "resolved": "https://registry.npmjs.org/debug/-/debug-4.3.1.tgz",
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+    "lodash-es": {
+      "version": "4.17.21",
+      "resolved": "https://registry.npmjs.org/lodash-es/-/lodash-es-4.17.21.tgz",
+      "integrity": "sha512-mKnC+QJ9pWVzv+C4/U3rRsHapFfHvQFoFB92e52xeyGMcX6/OlIl78je1u8vePzYZSkkogMPJ2yjxxsb89cxyw=="
     },
     "lodash.clonedeep": {
       "version": "4.5.0",
@@ -16939,7 +17102,6 @@
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-6.0.0.tgz",
       "integrity": "sha512-Jo6dJ04CmSjuznwJSS3pUeWmd/H0ffTlkXXgwZi+eq1UCmqQwCh+eLsYOYCwY991i2Fah4h1BEMCx4qThGbsiA==",
-      "dev": true,
       "requires": {
         "yallist": "^4.0.0"
       }
@@ -17249,8 +17411,7 @@
     "ms": {
       "version": "2.1.2",
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz",
-      "integrity": "sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w==",
+      "integrity": "sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w=="
-      "dev": true
     },
     "multicast-dns": {
       "version": "6.2.3",
@@ -17441,6 +17602,11 @@
         "es-abstract": "^1.18.2"
       }
     },
+    "observable-fns": {
+      "version": "0.5.1",
+      "resolved": "https://registry.npmjs.org/observable-fns/-/observable-fns-0.5.1.tgz",
+      "integrity": "sha512-wf7g4Jpo1Wt2KIqZKLGeiuLOEMqpaOZ5gJn7DmSdqXgTdxRwSdBhWegQQpPteQ2gZvzCKqNNpwb853wcpA0j7A=="
+    },
     "obuf": {
       "version": "1.1.2",
       "resolved": "https://registry.npmjs.org/obuf/-/obuf-1.1.2.tgz",
@@ -17599,6 +17765,11 @@
       "integrity": "sha512-R4nPAVTAU0B9D35/Gk3uJf/7XYbQcyohSKdvAxIRSNghFl4e71hVoGnBNQz9cWaXxO2I10KTC+3jMdvvoKw6dQ==",
       "dev": true
     },
+    "pako": {
+      "version": "1.0.11",
+      "resolved": "https://registry.npmjs.org/pako/-/pako-1.0.11.tgz",
+      "integrity": "sha512-4hLB8Py4zZce5s4yd9XzopqwVv/yGNhV1Bl8NTmCq1763HeK2+EwVTv+leGeL13Dnh2wfbqowVPXCIO0z4taYw=="
+    },
     "parent-module": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/parent-module/-/parent-module-1.0.1.tgz",
@@ -17608,6 +17779,11 @@
         "callsites": "^3.0.0"
       }
     },
+    "parse-headers": {
+      "version": "2.0.3",
+      "resolved": "https://registry.npmjs.org/parse-headers/-/parse-headers-2.0.3.tgz",
+      "integrity": "sha512-QhhZ+DCCit2Coi2vmAKbq5RGTRcQUOE2+REgv8vdyu7MnYx2eZztegqtTx99TZ86GTIwqiy3+4nQTWZ2tgmdCA=="
+    },
     "parse-json": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/parse-json/-/parse-json-4.0.0.tgz",
@@ -18178,7 +18354,6 @@
       "version": "3.6.0",
       "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.0.tgz",
       "integrity": "sha512-BViHy7LKeTz4oNnkcLJ+lVSL6vpiFeX6/d3oSH8zCW7UxP2onchk+vTGB143xuFjHS3deTgkKoXXymXqymiIdA==",
-      "dev": true,
       "requires": {
         "inherits": "^2.0.3",
         "string_decoder": "^1.1.1",
@@ -19015,7 +19190,6 @@
       "version": "1.3.0",
       "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz",
       "integrity": "sha512-hkRX8U1WjJFd8LsDJ2yQ/wWWxaopEsABU1XfkM8A+j0+85JAGppt16cr1Whg6KIbb4okU6Mql6BOj+uup/wKeA==",
-      "dev": true,
       "requires": {
         "safe-buffer": "~5.2.0"
       },
@@ -19023,8 +19197,7 @@
         "safe-buffer": {
           "version": "5.2.1",
           "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.2.1.tgz",
-          "integrity": "sha512-rp3So07KcdmmKbGvgaNxQSJr7bGVSVk5S9Eq1F+ppbRo70+YeaDxkw5Dd8NPN+GD6bjnYm2VuPuCXmpuYvmCXQ==",
+          "integrity": "sha512-rp3So07KcdmmKbGvgaNxQSJr7bGVSVk5S9Eq1F+ppbRo70+YeaDxkw5Dd8NPN+GD6bjnYm2VuPuCXmpuYvmCXQ=="
-          "dev": true
         }
       }
     },
@@ -19274,18 +19447,48 @@
       "integrity": "sha1-f17oI66AUgfACvLfSoTsP8+lcLQ=",
       "dev": true
     },
+    "threads": {
+      "version": "1.6.4",
+      "resolved": "https://registry.npmjs.org/threads/-/threads-1.6.4.tgz",
+      "integrity": "sha512-A+9MQFAUha9W8MjIPmrvETy98qVmZFr5Unox9D95y7kvz3fBpGiFS7JOZs07B2KvTHoRNI5MrGudRVeCmv4Alw==",
+      "requires": {
+        "callsites": "^3.1.0",
+        "debug": "^4.2.0",
+        "is-observable": "^2.1.0",
+        "observable-fns": "^0.5.1",
+        "tiny-worker": ">= 2"
+      }
+    },
     "through": {
       "version": "2.3.8",
       "resolved": "https://registry.npmjs.org/through/-/through-2.3.8.tgz",
       "integrity": "sha1-DdTJ/6q8NXlgsbckEV1+Doai4fU=",
       "dev": true
     },
+    "through2": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/through2/-/through2-3.0.2.tgz",
+      "integrity": "sha512-enaDQ4MUyP2W6ZyT6EsMzqBPZaM/avg8iuo+l2d3QCs0J+6RaqkHV/2/lOwDTueBHeJ/2LG9lrLW3d5rWPucuQ==",
+      "requires": {
+        "inherits": "^2.0.4",
+        "readable-stream": "2 || 3"
+      }
+    },
     "thunky": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/thunky/-/thunky-1.1.0.tgz",
       "integrity": "sha512-eHY7nBftgThBqOyHGVN+l8gF0BucP09fMo0oO/Lb0w1OF80dJv+lDVpXG60WMQvkcxAkNybKsrEIE3ZtKGmPrA==",
       "dev": true
     },
+    "tiny-worker": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/tiny-worker/-/tiny-worker-2.3.0.tgz",
+      "integrity": "sha512-pJ70wq5EAqTAEl9IkGzA+fN0836rycEuz2Cn6yeZ6FRzlVS5IDOkFHpIoEsksPRQV34GDqXm65+OlnZqUSyK2g==",
+      "optional": true,
+      "requires": {
+        "esm": "^3.2.25"
+      }
+    },
     "tmp": {
       "version": "0.2.1",
       "resolved": "https://registry.npmjs.org/tmp/-/tmp-0.2.1.tgz",
@@ -19364,6 +19567,14 @@
       "integrity": "sha1-WuaBd/GS1EViadEIr6k/+HQ/T2Q=",
       "dev": true
     },
+    "txml": {
+      "version": "3.2.5",
+      "resolved": "https://registry.npmjs.org/txml/-/txml-3.2.5.tgz",
+      "integrity": "sha512-AtN8AgJLiDanttIXJaQlxH8/R0NOCNwto8kcO7BaxdLgsN9b7itM9lnTD7c2O3TadP+hHB9j7ra5XGFRPNnk/g==",
+      "requires": {
+        "through2": "^3.0.1"
+      }
+    },
     "type-check": {
       "version": "0.4.0",
       "resolved": "https://registry.npmjs.org/type-check/-/type-check-0.4.0.tgz",
@@ -19518,8 +19729,7 @@
     "util-deprecate": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
-      "integrity": "sha1-RQ1Nyfpw3nMnYvvS1KKJgUGaDM8=",
+      "integrity": "sha1-RQ1Nyfpw3nMnYvvS1KKJgUGaDM8="
-      "dev": true
     },
     "utils-merge": {
       "version": "1.0.1",
@@ -20044,8 +20254,7 @@
     "yallist": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
-      "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A==",
+      "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A=="
-      "dev": true
     },
     "yargs": {
       "version": "17.1.1",

package.json

@@ -45,6 +45,7 @@
     "url": "https://opencollective.com/openlayers"
   },
   "dependencies": {
+    "geotiff": "^1.0.0-beta.16",
     "ol-mapbox-style": "^6.4.1",
     "pbf": "3.2.1",
     "rbush": "^3.0.1"

src/ol/DataTile.js

@@ -0,0 +1,76 @@
+/**
+ * @module ol/DataTile
+ */
+import Tile from './Tile.js';
+import TileState from './TileState.js';
+
+/**
+ * Data that can be used with a DataTile.
+ * @typedef {Uint8Array|Uint8ClampedArray|DataView} Data
+ */
+
+/**
+ * @typedef {Object} Options
+ * @property {import("./tilecoord.js").TileCoord} tileCoord Tile coordinate.
+ * @property {function() : Promise<Data>} loader Data loader.
+ * @property {number} [transition=250] A duration for tile opacity
+ * transitions in milliseconds. A duration of 0 disables the opacity transition.
+ * @api
+ */
+
+class DataTile extends Tile {
+  /**
+   * @param {Options} options Tile options.
+   */
+  constructor(options) {
+    const state = TileState.IDLE;
+
+    super(options.tileCoord, state, {transition: options.transition});
+
+    this.loader_ = options.loader;
+    this.data_ = null;
+    this.error_ = null;
+  }
+
+  /**
+   * Get the data for the tile.
+   * @return {Data} Tile data.
+   * @api
+   */
+  getData() {
+    return this.data_;
+  }
+
+  /**
+   * Get any loading error.
+   * @return {Error} Loading error.
+   * @api
+   */
+  getError() {
+    return this.error_;
+  }
+
+  /**
+   * Load not yet loaded URI.
+   * @api
+   */
+  load() {
+    this.state = TileState.LOADING;
+    this.changed();
+
+    const self = this;
+    this.loader_()
+      .then(function (data) {
+        self.data_ = data;
+        self.state = TileState.LOADED;
+        self.changed();
+      })
+      .catch(function (error) {
+        self.error_ = error;
+        self.state = TileState.ERROR;
+        self.changed();
+      });
+  }
+}
+
+export default DataTile;

src/ol/layer/WebGLTile.js

@@ -0,0 +1,289 @@
+/**
+ * @module ol/layer/WebGLTile
+ */
+import BaseTileLayer from './BaseTile.js';
+import WebGLTileLayerRenderer, {
+  Attributes,
+  Uniforms,
+} from '../renderer/webgl/TileLayer.js';
+import {
+  ValueTypes,
+  expressionToGlsl,
+  getStringNumberEquivalent,
+  uniformNameForVariable,
+} from '../style/expressions.js';
+import {assign} from '../obj.js';
+
+/**
+ * @typedef {Object} Style
+ * @property {Object<string, number>} [variables] Style variables.  Each variable must hold a number.
+ * @property {import("../style/expressions.js").ExpressionValue} [color] An expression applied to color values.
+ * @property {import("../style/expressions.js").ExpressionValue} [brightness=0] Value used to decrease or increase
+ * the layer brightness.  Values range from -1 to 1.
+ * @property {import("../style/expressions.js").ExpressionValue} [contrast=0] Value used to decrease or increase
+ * the layer contrast.  Values range from -1 to 1.
+ * @property {import("../style/expressions.js").ExpressionValue} [exposure=0] Value used to decrease or increase
+ * the layer exposure.  Values range from -1 to 1.
+ * @property {import("../style/expressions.js").ExpressionValue} [saturation=0] Value used to decrease or increase
+ * the layer saturation.  Values range from -1 to 1.
+ * @property {import("../style/expressions.js").ExpressionValue} [gamma=1] Apply a gamma correction to the layer.
+ * Values range from 0 to infinity.
+ */
+
+/**
+ * @typedef {Object} Options
+ * @property {Style} [style] Style to apply to the layer.
+ * @property {string} [className='ol-layer'] A CSS class name to set to the layer element.
+ * @property {number} [opacity=1] Opacity (0, 1).
+ * @property {boolean} [visible=true] Visibility.
+ * @property {import("../extent.js").Extent} [extent] The bounding extent for layer rendering.  The layer will not be
+ * rendered outside of this extent.
+ * @property {number} [zIndex] The z-index for layer rendering.  At rendering time, the layers
+ * will be ordered, first by Z-index and then by position. When `undefined`, a `zIndex` of 0 is assumed
+ * for layers that are added to the map's `layers` collection, or `Infinity` when the layer's `setMap()`
+ * method was used.
+ * @property {number} [minResolution] The minimum resolution (inclusive) at which this layer will be
+ * visible.
+ * @property {number} [maxResolution] The maximum resolution (exclusive) below which this layer will
+ * be visible.
+ * @property {number} [minZoom] The minimum view zoom level (exclusive) above which this layer will be
+ * visible.
+ * @property {number} [maxZoom] The maximum view zoom level (inclusive) at which this layer will
+ * be visible.
+ * @property {number} [preload=0] Preload. Load low-resolution tiles up to `preload` levels. `0`
+ * means no preloading.
+ * @property {import("../source/Tile.js").default} [source] Source for this layer.
+ * @property {import("../PluggableMap.js").default} [map] Sets the layer as overlay on a map. The map will not manage
+ * this layer in its layers collection, and the layer will be rendered on top. This is useful for
+ * temporary layers. The standard way to add a layer to a map and have it managed by the map is to
+ * use {@link module:ol/Map#addLayer}.
+ * @property {boolean} [useInterimTilesOnError=true] Use interim tiles on error.
+ */
+
+/**
+ * @typedef {Object} ParsedStyle
+ * @property {string} vertexShader The vertex shader.
+ * @property {string} fragmentShader The fragment shader.
+ * @property {Object<string,import("../webgl/Helper.js").UniformValue>} uniforms Uniform definitions.
+ */
+
+/**
+ * @param {Style} style The layer style.
+ * @param {number} bandCount The number of bands.
+ * @return {ParsedStyle} Shaders and uniforms generated from the style.
+ */
+function parseStyle(style, bandCount) {
+  const vertexShader = `
+    attribute vec2 ${Attributes.TEXTURE_COORD};
+    uniform mat4 ${Uniforms.TILE_TRANSFORM};
+    uniform float ${Uniforms.DEPTH};
+
+    varying vec2 v_textureCoord;
+
+    void main() {
+      v_textureCoord = ${Attributes.TEXTURE_COORD};
+      gl_Position = ${Uniforms.TILE_TRANSFORM} * vec4(${Attributes.TEXTURE_COORD}, ${Uniforms.DEPTH}, 1.0);
+    }
+  `;
+
+  /**
+   * @type {import("../style/expressions.js").ParsingContext}
+   */
+  const context = {
+    inFragmentShader: true,
+    variables: [],
+    attributes: [],
+    stringLiteralsMap: {},
+    bandCount: bandCount,
+  };
+
+  const pipeline = [];
+
+  if (style.color !== undefined) {
+    const color = expressionToGlsl(context, style.color, ValueTypes.COLOR);
+    pipeline.push(`color = ${color};`);
+  }
+
+  if (style.contrast !== undefined) {
+    const contrast = expressionToGlsl(
+      context,
+      style.contrast,
+      ValueTypes.NUMBER
+    );
+    pipeline.push(
+      `color.rgb = clamp((${contrast} + 1.0) * color.rgb - (${contrast} / 2.0), vec3(0.0, 0.0, 0.0), vec3(1.0, 1.0, 1.0));`
+    );
+  }
+
+  if (style.exposure !== undefined) {
+    const exposure = expressionToGlsl(
+      context,
+      style.exposure,
+      ValueTypes.NUMBER
+    );
+    pipeline.push(
+      `color.rgb = clamp((${exposure} + 1.0) * color.rgb, vec3(0.0, 0.0, 0.0), vec3(1.0, 1.0, 1.0));`
+    );
+  }
+
+  if (style.saturation !== undefined) {
+    const saturation = expressionToGlsl(
+      context,
+      style.saturation,
+      ValueTypes.NUMBER
+    );
+    pipeline.push(`
+      float saturation = ${saturation} + 1.0;
+      float sr = (1.0 - saturation) * 0.2126;
+      float sg = (1.0 - saturation) * 0.7152;
+      float sb = (1.0 - saturation) * 0.0722;
+      mat3 saturationMatrix = mat3(
+        sr + saturation, sr, sr,
+        sg, sg + saturation, sg,
+        sb, sb, sb + saturation
+      );
+      color.rgb = clamp(saturationMatrix * color.rgb, vec3(0.0, 0.0, 0.0), vec3(1.0, 1.0, 1.0));
+    `);
+  }
+
+  if (style.gamma !== undefined) {
+    const gamma = expressionToGlsl(context, style.gamma, ValueTypes.NUMBER);
+    pipeline.push(`color.rgb = pow(color.rgb, vec3(1.0 / ${gamma}));`);
+  }
+
+  if (style.brightness !== undefined) {
+    const brightness = expressionToGlsl(
+      context,
+      style.brightness,
+      ValueTypes.NUMBER
+    );
+    pipeline.push(
+      `color.rgb = clamp(color.rgb + ${brightness}, vec3(0.0, 0.0, 0.0), vec3(1.0, 1.0, 1.0));`
+    );
+  }
+
+  /** @type {Object<string,import("../webgl/Helper").UniformValue>} */
+  const uniforms = {};
+
+  const numVariables = context.variables.length;
+  if (numVariables > 1 && !style.variables) {
+    throw new Error(
+      `Missing variables in style (expected ${context.variables})`
+    );
+  }
+
+  for (let i = 0; i < numVariables; ++i) {
+    const variableName = context.variables[i];
+    if (!(variableName in style.variables)) {
+      throw new Error(`Missing '${variableName}' in style variables`);
+    }
+    const uniformName = uniformNameForVariable(variableName);
+    uniforms[uniformName] = function () {
+      let value = style.variables[variableName];
+      if (typeof value === 'string') {
+        value = getStringNumberEquivalent(context, value);
+      }
+      return value !== undefined ? value : -9999999; // to avoid matching with the first string literal
+    };
+  }
+
+  const uniformDeclarations = Object.keys(uniforms).map(function (name) {
+    return `uniform float ${name};`;
+  });
+
+  const textureCount = Math.ceil(bandCount / 4);
+  const colorAssignments = new Array(textureCount);
+  for (let textureIndex = 0; textureIndex < textureCount; ++textureIndex) {
+    const uniformName = Uniforms.TILE_TEXTURE_PREFIX + textureIndex;
+    uniformDeclarations.push(`uniform sampler2D ${uniformName};`);
+    colorAssignments[
+      textureIndex
+    ] = `vec4 color${textureIndex} = texture2D(${uniformName}, v_textureCoord);`;
+  }
+
+  const fragmentShader = `
+    #ifdef GL_FRAGMENT_PRECISION_HIGH
+    precision highp float;
+    #else
+    precision mediump float;
+    #endif
+
+    varying vec2 v_textureCoord;
+    uniform float ${Uniforms.TRANSITION_ALPHA};
+
+    ${uniformDeclarations.join('\n')}
+
+    void main() {
+      ${colorAssignments.join('\n')}
+
+      vec4 color = color0;
+
+      ${pipeline.join('\n')}
+
+      if (color.a == 0.0) {
+        discard;
+      }
+
+      gl_FragColor = color * ${Uniforms.TRANSITION_ALPHA};
+    }`;
+
+  return {
+    vertexShader: vertexShader,
+    fragmentShader: fragmentShader,
+    uniforms: uniforms,
+  };
+}
+
+/**
+ * @classdesc
+ * For layer sources that provide pre-rendered, tiled images in grids that are
+ * organized by zoom levels for specific resolutions.
+ * Note that any property set in the options is set as a {@link module:ol/Object~BaseObject}
+ * property on the layer object; for example, setting `title: 'My Title'` in the
+ * options means that `title` is observable, and has get/set accessors.
+ *
+ * @api
+ */
+class WebGLTileLayer extends BaseTileLayer {
+  /**
+   * @param {Options} opt_options Tile layer options.
+   */
+  constructor(opt_options) {
+    const options = opt_options ? assign({}, opt_options) : {};
+
+    const style = options.style || {};
+    delete options.style;
+    super(options);
+
+    const parsedStyle = parseStyle(style || {}, 1); // TODO: get texture count from source
+
+    this.vertexShader_ = parsedStyle.vertexShader;
+    this.fragmentShader_ = parsedStyle.fragmentShader;
+    this.uniforms_ = parsedStyle.uniforms;
+    this.styleVariables_ = style.variables || {};
+  }
+
+  /**
+   * Create a renderer for this layer.
+   * @return {import("../renderer/Layer.js").default} A layer renderer.
+   * @protected
+   */
+  createRenderer() {
+    return new WebGLTileLayerRenderer(this, {
+      vertexShader: this.vertexShader_,
+      fragmentShader: this.fragmentShader_,
+      uniforms: this.uniforms_,
+    });
+  }
+
+  /**
+   * Update any variables used by the layer style and trigger a re-render.
+   * @param {Object<string, number>} variables Variables to update.
+   */
+  updateStyleVariables(variables) {
+    assign(this.styleVariables_, variables);
+    this.changed();
+  }
+}
+
+export default WebGLTileLayer;

src/ol/renderer/webgl/TileLayer.js

@@ -0,0 +1,487 @@
+/**
+ * @module ol/renderer/webgl/TileLayer
+ */
+import LRUCache from '../../structs/LRUCache.js';
+import State from '../../source/State.js';
+import TileRange from '../../TileRange.js';
+import TileState from '../../TileState.js';
+import TileTexture from '../../webgl/TileTexture.js';
+import WebGLArrayBuffer from '../../webgl/Buffer.js';
+import WebGLLayerRenderer from './Layer.js';
+import {AttributeType} from '../../webgl/Helper.js';
+import {ELEMENT_ARRAY_BUFFER, STATIC_DRAW} from '../../webgl.js';
+import {
+  compose as composeTransform,
+  create as createTransform,
+} from '../../transform.js';
+import {
+  create as createMat4,
+  fromTransform as mat4FromTransform,
+} from '../../vec/mat4.js';
+import {
+  createOrUpdate as createTileCoord,
+  getKeyZXY,
+  getKey as getTileCoordKey,
+} from '../../tilecoord.js';
+import {fromUserExtent} from '../../proj.js';
+import {getIntersection} from '../../extent.js';
+import {getUid} from '../../util.js';
+import {numberSafeCompareFunction} from '../../array.js';
+import {toSize} from '../../size.js';
+
+export const Uniforms = {
+  TILE_TEXTURE_PREFIX: 'u_tileTexture',
+  TILE_TRANSFORM: 'u_tileTransform',
+  TRANSITION_ALPHA: 'u_transitionAlpha',
+  DEPTH: 'u_depth',
+};
+
+export const Attributes = {
+  TEXTURE_COORD: 'a_textureCoord',
+};
+
+/**
+ * @type {Array<import('../../webgl/Helper.js').AttributeDescription>}
+ */
+const attributeDescriptions = [
+  {
+    name: Attributes.TEXTURE_COORD,
+    size: 2,
+    type: AttributeType.FLOAT,
+  },
+];
+
+/**
+ * Transform a zoom level into a depth value ranging from -1 to 1.
+ * @param {number} z A zoom level.
+ * @return {number} A depth value.
+ */
+function depthForZ(z) {
+  return 2 * (1 - 1 / (z + 1)) - 1;
+}
+
+/**
+ * Add a tile texture to the lookup.
+ * @param {Object<string, Array<import("../../webgl/TileTexture.js").default>>} tileTexturesByZ Lookup of
+ * tile textures by zoom level.
+ * @param {import("../../webgl/TileTexture.js").default} tileTexture A tile texture.
+ * @param {number} z The zoom level.
+ */
+function addTileTextureToLookup(tileTexturesByZ, tileTexture, z) {
+  if (!(z in tileTexturesByZ)) {
+    tileTexturesByZ[z] = [];
+  }
+  tileTexturesByZ[z].push(tileTexture);
+}
+
+/**
+ * @typedef {Object} Options
+ * @property {string} vertexShader Vertex shader source.
+ * @property {string} fragmentShader Fragment shader source.
+ * @property {Object<string, import("../../webgl/Helper").UniformValue>} [uniforms] Additional uniforms
+ * made available to shaders.
+ * @property {string} [className='ol-layer'] A CSS class name to set to the canvas element.
+ */
+
+/**
+ * @classdesc
+ * WebGL renderer for tile layers.
+ * @api
+ */
+class WebGLTileLayerRenderer extends WebGLLayerRenderer {
+  /**
+   * @param {import("../../layer/WebGLTile.js").default} tileLayer Tile layer.
+   * @param {Options} options Options.
+   */
+  constructor(tileLayer, options) {
+    super(tileLayer, {
+      uniforms: options.uniforms,
+      className: options.className,
+    });
+
+    /**
+     * This transform converts tile i, j coordinates to screen coordinates.
+     * @type {import("../../transform.js").Transform}
+     * @private
+     */
+    this.tileTransform_ = createTransform();
+
+    /**
+     * @type {Array<number>}
+     * @private
+     */
+    this.tempMat4_ = createMat4();
+
+    /**
+     * @type {import("../../TileRange.js").default}
+     * @private
+     */
+    this.tempTileRange_ = new TileRange(0, 0, 0, 0);
+
+    /**
+     * @type {import("../../tilecoord.js").TileCoord}
+     * @private
+     */
+    this.tempTileCoord_ = createTileCoord(0, 0, 0);
+
+    /**
+     * @type {import("../../size.js").Size}
+     * @private
+     */
+    this.tempSize_ = [0, 0];
+
+    this.program_ = this.helper.getProgram(
+      options.fragmentShader,
+      options.vertexShader
+    );
+
+    /**
+     * Tiles are rendered as a quad with the following structure:
+     *
+     *  [P3]---------[P2]
+     *   |`           |
+     *   |  `     B   |
+     *   |    `       |
+     *   |      `     |
+     *   |   A    `   |
+     *   |          ` |
+     *  [P0]---------[P1]
+     *
+     * Triangle A: P0, P1, P3
+     * Triangle B: P1, P2, P3
+     */
+    const indices = new WebGLArrayBuffer(ELEMENT_ARRAY_BUFFER, STATIC_DRAW);
+    indices.fromArray([0, 1, 3, 1, 2, 3]);
+    this.helper.flushBufferData(indices);
+    this.indices_ = indices;
+
+    this.tileTextureCache_ = new LRUCache(512);
+
+    this.renderedOpacity_ = NaN;
+  }
+
+  /**
+   * Determine whether render should be called.
+   * @param {import("../../PluggableMap.js").FrameState} frameState Frame state.
+   * @return {boolean} Layer is ready to be rendered.
+   */
+  prepareFrame(frameState) {
+    const source = this.getLayer().getSource();
+    if (!source) {
+      return false;
+    }
+    return source.getState() === State.READY;
+  }
+
+  /**
+   * Render the layer.
+   * @param {import("../../PluggableMap.js").FrameState} frameState Frame state.
+   * @return {HTMLElement} The rendered element.
+   */
+  renderFrame(frameState) {
+    this.preRender(frameState);
+
+    const layerState = frameState.layerStatesArray[frameState.layerIndex];
+    const viewState = frameState.viewState;
+
+    let extent = frameState.extent;
+    if (layerState.extent) {
+      extent = getIntersection(
+        extent,
+        fromUserExtent(layerState.extent, viewState.projection)
+      );
+    }
+
+    const tileLayer = this.getLayer();
+    const tileSource = tileLayer.getSource();
+    const tileGrid = tileSource.getTileGridForProjection(viewState.projection);
+    const z = tileGrid.getZForResolution(
+      viewState.resolution,
+      tileSource.zDirection
+    );
+
+    /**
+     * @type {Object<string, Array<import("../../webgl/TileTexture.js").default>>}
+     */
+    const tileTexturesByZ = {};
+
+    const tileTextureCache = this.tileTextureCache_;
+    const tileRange = tileGrid.getTileRangeForExtentAndZ(extent, z);
+
+    const tileSourceKey = getUid(tileSource);
+    if (!(tileSourceKey in frameState.wantedTiles)) {
+      frameState.wantedTiles[tileSourceKey] = {};
+    }
+
+    const wantedTiles = frameState.wantedTiles[tileSourceKey];
+
+    const tileResolution = tileGrid.getResolution(z);
+
+    for (let x = tileRange.minX; x <= tileRange.maxX; ++x) {
+      for (let y = tileRange.minY; y <= tileRange.maxY; ++y) {
+        const tileCoord = createTileCoord(z, x, y, this.tempTileCoord_);
+        const tileCoordKey = getTileCoordKey(tileCoord);
+
+        let tileTexture;
+        if (tileTextureCache.containsKey(tileCoordKey)) {
+          tileTexture = tileTextureCache.get(tileCoordKey);
+        } else {
+          const tile = tileSource.getTile(
+            z,
+            x,
+            y,
+            frameState.pixelRatio,
+            viewState.projection
+          );
+          tileTexture = new TileTexture(tile, tileGrid, this.helper);
+          tileTextureCache.set(tileCoordKey, tileTexture);
+        }
+
+        addTileTextureToLookup(tileTexturesByZ, tileTexture, z);
+
+        const tileQueueKey = tileTexture.tile.getKey();
+        wantedTiles[tileQueueKey] = true;
+
+        if (tileTexture.tile.getState() === TileState.IDLE) {
+          if (!frameState.tileQueue.isKeyQueued(tileQueueKey)) {
+            frameState.tileQueue.enqueue([
+              tileTexture.tile,
+              tileSourceKey,
+              tileGrid.getTileCoordCenter(tileCoord),
+              tileResolution,
+            ]);
+          }
+        }
+      }
+    }
+
+    /**
+     * A lookup of alpha values for tiles at the target rendering resolution
+     * for tiles that are in transition.  If a tile coord key is absent from
+     * this lookup, the tile should be rendered at alpha 1.
+     * @type {Object<string, number>}
+     */
+    const alphaLookup = {};
+
+    const uid = getUid(this);
+    const time = frameState.time;
+
+    // look for cached tiles to use if a target tile is not ready
+    const tileTextures = tileTexturesByZ[z];
+    for (let i = 0, ii = tileTextures.length; i < ii; ++i) {
+      const tileTexture = tileTextures[i];
+      const tile = tileTexture.tile;
+      const tileCoord = tile.tileCoord;
+
+      if (tileTexture.loaded) {
+        const alpha = tile.getAlpha(uid, time);
+        if (alpha === 1) {
+          // no need to look for alt tiles
+          tile.endTransition(uid);
+          continue;
+        }
+        const tileCoordKey = getTileCoordKey(tileCoord);
+        alphaLookup[tileCoordKey] = alpha;
+      }
+
+      // first look for child tiles (at z + 1)
+      const coveredByChildren = this.findAltTiles_(
+        tileGrid,
+        tileCoord,
+        z + 1,
+        tileTexturesByZ
+      );
+
+      if (coveredByChildren) {
+        continue;
+      }
+
+      // next look for parent tiles
+      for (let parentZ = z - 1; parentZ >= tileGrid.minZoom; --parentZ) {
+        const coveredByParent = this.findAltTiles_(
+          tileGrid,
+          tileCoord,
+          parentZ,
+          tileTexturesByZ
+        );
+
+        if (coveredByParent) {
+          break;
+        }
+      }
+    }
+
+    this.helper.useProgram(this.program_);
+    this.helper.prepareDraw(frameState);
+
+    const zs = Object.keys(tileTexturesByZ)
+      .map(Number)
+      .sort(numberSafeCompareFunction);
+
+    const gl = this.helper.getGL();
+
+    const centerX = viewState.center[0];
+    const centerY = viewState.center[1];
+
+    for (let j = 0, jj = zs.length; j < jj; ++j) {
+      const tileZ = zs[j];
+      const tileResolution = tileGrid.getResolution(tileZ);
+      const tileSize = toSize(tileGrid.getTileSize(tileZ), this.tempSize_);
+      const tileOrigin = tileGrid.getOrigin(tileZ);
+
+      const centerI =
+        (centerX - tileOrigin[0]) / (tileSize[0] * tileResolution);
+      const centerJ =
+        (tileOrigin[1] - centerY) / (tileSize[1] * tileResolution);
+
+      const tileScale = viewState.resolution / tileResolution;
+
+      const depth = depthForZ(tileZ);
+      const tileTextures = tileTexturesByZ[tileZ];
+      for (let i = 0, ii = tileTextures.length; i < ii; ++i) {
+        const tileTexture = tileTextures[i];
+        if (!tileTexture.loaded) {
+          continue;
+        }
+        const tile = tileTexture.tile;
+        const tileCoord = tile.tileCoord;
+        const tileCoordKey = getTileCoordKey(tileCoord);
+
+        const tileCenterI = tileCoord[1];
+        const tileCenterJ = tileCoord[2];
+
+        composeTransform(
+          this.tileTransform_,
+          0,
+          0,
+          2 / ((frameState.size[0] * tileScale) / tileSize[0]),
+          -2 / ((frameState.size[1] * tileScale) / tileSize[1]),
+          viewState.rotation,
+          -(centerI - tileCenterI),
+          -(centerJ - tileCenterJ)
+        );
+
+        this.helper.setUniformMatrixValue(
+          Uniforms.TILE_TRANSFORM,
+          mat4FromTransform(this.tempMat4_, this.tileTransform_)
+        );
+
+        this.helper.bindBuffer(tileTexture.coords);
+        this.helper.bindBuffer(this.indices_);
+        this.helper.enableAttributes(attributeDescriptions);
+
+        for (
+          let textureIndex = 0;
+          textureIndex < tileTexture.textures.length;
+          ++textureIndex
+        ) {
+          const textureProperty = 'TEXTURE' + textureIndex;
+          const uniformName = Uniforms.TILE_TEXTURE_PREFIX + textureIndex;
+          gl.activeTexture(gl[textureProperty]);
+          gl.bindTexture(gl.TEXTURE_2D, tileTexture.textures[textureIndex]);
+          gl.uniform1i(this.helper.getUniformLocation(uniformName), 0);
+        }
+
+        const alpha =
+          tileCoordKey in alphaLookup ? alphaLookup[tileCoordKey] : 1;
+
+        if (alpha < 1) {
+          frameState.animate = true;
+        }
+
+        this.helper.setUniformFloatValue(Uniforms.TRANSITION_ALPHA, alpha);
+        this.helper.setUniformFloatValue(Uniforms.DEPTH, depth);
+
+        this.helper.drawElements(0, this.indices_.getSize());
+      }
+    }
+
+    this.helper.finalizeDraw(frameState);
+
+    const canvas = this.helper.getCanvas();
+
+    const opacity = layerState.opacity;
+    if (this.renderedOpacity_ !== opacity) {
+      canvas.style.opacity = String(opacity);
+      this.renderedOpacity_ = opacity;
+    }
+
+    while (tileTextureCache.canExpireCache()) {
+      const tileTexture = tileTextureCache.pop();
+      tileTexture.dispose();
+    }
+
+    // TODO: let the renderers manage their own cache instead of managing the source cache
+    if (tileSource.canExpireCache()) {
+      /**
+       * @param {import("../../PluggableMap.js").default} map Map.
+       * @param {import("../../PluggableMap.js").FrameState} frameState Frame state.
+       */
+      const postRenderFunction = function (map, frameState) {
+        const tileSourceKey = getUid(tileSource);
+        if (tileSourceKey in frameState.usedTiles) {
+          tileSource.expireCache(
+            frameState.viewState.projection,
+            frameState.usedTiles[tileSourceKey]
+          );
+        }
+      };
+
+      frameState.postRenderFunctions.push(postRenderFunction);
+    }
+
+    this.postRender(frameState);
+    return canvas;
+  }
+
+  /**
+   * Look for tiles covering the provided tile coordinate at an alternate
+   * zoom level.  Loaded tiles will be added to the provided tile texture lookup.
+   * @param {import("../../tilegrid/TileGrid.js").default} tileGrid The tile grid.
+   * @param {import("../../tilecoord.js").TileCoord} tileCoord The target tile coordinate.
+   * @param {number} altZ The alternate zoom level.
+   * @param {Object<string, Array<import("../../webgl/TileTexture.js").default>>} tileTexturesByZ Lookup of
+   * tile textures by zoom level.
+   * @return {boolean} The tile coordinate is covered by loaded tiles at the alternate zoom level.
+   * @private
+   */
+  findAltTiles_(tileGrid, tileCoord, altZ, tileTexturesByZ) {
+    const tileRange = tileGrid.getTileRangeForTileCoordAndZ(
+      tileCoord,
+      altZ,
+      this.tempTileRange_
+    );
+
+    if (!tileRange) {
+      return false;
+    }
+
+    let covered = true;
+    const tileTextureCache = this.tileTextureCache_;
+    for (let x = tileRange.minX; x <= tileRange.maxX; ++x) {
+      for (let y = tileRange.minY; y <= tileRange.maxY; ++y) {
+        const cacheKey = getKeyZXY(altZ, x, y);
+        let loaded = false;
+        if (tileTextureCache.containsKey(cacheKey)) {
+          const tileTexture = tileTextureCache.get(cacheKey);
+          if (tileTexture.loaded) {
+            addTileTextureToLookup(tileTexturesByZ, tileTexture, altZ);
+            loaded = true;
+          }
+        }
+        if (!loaded) {
+          covered = false;
+        }
+      }
+    }
+    return covered;
+  }
+}
+
+/**
+ * @function
+ * @return {import("../../layer/WebGLTile.js").default}
+ */
+WebGLTileLayerRenderer.prototype.getLayer;
+
+export default WebGLTileLayerRenderer;

src/ol/source/DataTile.js

@@ -0,0 +1,142 @@
+/**
+ * @module ol/source/DataTile
+ */
+import DataTile from '../DataTile.js';
+import EventType from '../events/EventType.js';
+import TileEventType from './TileEventType.js';
+import TileSource, {TileSourceEvent} from './Tile.js';
+import TileState from '../TileState.js';
+import {createXYZ, extentFromProjection} from '../tilegrid.js';
+import {getKeyZXY} from '../tilecoord.js';
+import {getUid} from '../util.js';
+
+/**
+ * @typedef {Object} Options
+ * @property {function(number, number, number) : Promise<import("../DataTile.js").Data>} [loader] Data loader.  Called with z, x, and y tile coordinates.
+ * @property {number} [maxZoom=42] Optional max zoom level. Not used if `tileGrid` is provided.
+ * @property {number} [minZoom=0] Optional min zoom level. Not used if `tileGrid` is provided.
+ * @property {number|import("../size.js").Size} [tileSize=[256, 256]] The pixel width and height of the tiles.
+ * @property {number} [maxResolution] Optional tile grid resolution at level zero. Not used if `tileGrid` is provided.
+ * @property {import("../proj.js").ProjectionLike} [projection='EPSG:3857'] Tile projection.
+ * @property {import("../tilegrid/TileGrid.js").default} [tileGrid] Tile grid.
+ * @property {boolean} [opaque=false] Whether the layer is opaque.
+ * @property {import("./State.js").default} [state] The source state.
+ * @property {number} [cacheSize] Number of tiles to retain in the cache.
+ * @property {number} [tilePixelRatio] Tile pixel ratio.
+ * @property {boolean} [wrapX=true] Render tiles beyond the antimeridian.
+ * @property {number} [transition] Transition time when fading in new tiles (in miliseconds).
+ */
+
+/**
+ * @classdesc
+ * Base class for sources providing tiles divided into a tile grid over http.
+ *
+ * @fires import("./Tile.js").TileSourceEvent
+ */
+class DataTileSource extends TileSource {
+  /**
+   * @param {Options} options Image tile options.
+   */
+  constructor(options) {
+    const projection =
+      options.projection === undefined ? 'EPSG:3857' : options.projection;
+
+    let tileGrid = options.tileGrid;
+    if (tileGrid === undefined && projection) {
+      tileGrid = createXYZ({
+        extent: extentFromProjection(projection),
+        maxResolution: options.maxResolution,
+        maxZoom: options.maxZoom,
+        minZoom: options.minZoom,
+        tileSize: options.tileSize,
+      });
+    }
+
+    super({
+      cacheSize: options.cacheSize,
+      projection: projection,
+      tileGrid: tileGrid,
+      opaque: options.opaque,
+      state: options.state,
+      tilePixelRatio: options.tilePixelRatio,
+      wrapX: options.wrapX,
+      transition: options.transition,
+    });
+
+    /**
+     * @private
+     * @type {!Object<string, boolean>}
+     */
+    this.tileLoadingKeys_ = {};
+
+    /**
+     * @private
+     */
+    this.loader_ = options.loader;
+
+    this.handleTileChange_ = this.handleTileChange_.bind(this);
+  }
+
+  /**
+   * @param {function(number, number, number) : Promise<import("../DataTile.js").Data>} loader The data loader.
+   * @protected
+   */
+  setLoader(loader) {
+    this.loader_ = loader;
+  }
+
+  /**
+   * @abstract
+   * @param {number} z Tile coordinate z.
+   * @param {number} x Tile coordinate x.
+   * @param {number} y Tile coordinate y.
+   * @param {number} pixelRatio Pixel ratio.
+   * @param {import("../proj/Projection.js").default} projection Projection.
+   * @return {!import("../Tile.js").default} Tile.
+   */
+  getTile(z, x, y, pixelRatio, projection) {
+    const tileCoordKey = getKeyZXY(z, x, y);
+    if (this.tileCache.containsKey(tileCoordKey)) {
+      return this.tileCache.get(tileCoordKey);
+    }
+
+    const sourceLoader = this.loader_;
+    function loader() {
+      return sourceLoader(z, x, y);
+    }
+
+    const tile = new DataTile({tileCoord: [z, x, y], loader: loader});
+    tile.addEventListener(EventType.CHANGE, this.handleTileChange_);
+
+    this.tileCache.set(tileCoordKey, tile);
+    return tile;
+  }
+
+  /**
+   * Handle tile change events.
+   * @param {import("../events/Event.js").default} event Event.
+   */
+  handleTileChange_(event) {
+    const tile = /** @type {import("../Tile.js").default} */ (event.target);
+    const uid = getUid(tile);
+    const tileState = tile.getState();
+    let type;
+    if (tileState == TileState.LOADING) {
+      this.tileLoadingKeys_[uid] = true;
+      type = TileEventType.TILELOADSTART;
+    } else if (uid in this.tileLoadingKeys_) {
+      delete this.tileLoadingKeys_[uid];
+      type =
+        tileState == TileState.ERROR
+          ? TileEventType.TILELOADERROR
+          : tileState == TileState.LOADED
+          ? TileEventType.TILELOADEND
+          : undefined;
+    }
+    if (type) {
+      this.dispatchEvent(new TileSourceEvent(type, tile));
+    }
+  }
+}
+
+export default DataTileSource;

src/ol/source/GeoTIFF.js

@@ -0,0 +1,391 @@
+/**
+ * @module ol/source/GeoTIFF
+ */
+import DataTile from './DataTile.js';
+import State from './State.js';
+import TileGrid from '../tilegrid/TileGrid.js';
+import {get as getProjection} from '../proj.js';
+import {fromUrl as tiffFromUrl, fromUrls as tiffFromUrls} from 'geotiff';
+import {toSize} from '../size.js';
+
+/**
+ * @typedef SourceInfo
+ * @property {string} url URL for the source.
+ * @property {Array<string>} [overviews] List of any overview URLs.
+ * @property {number} [min=0] The minimum source data value.  Rendered values are scaled from 0 to 1 based on
+ * the configured min and max.
+ * @property {number} [max] The maximum source data value.  Rendered values are scaled from 0 to 1 based on
+ * the configured min and max.
+ * @property {number} [nodata] Values to discard.
+ */
+
+/**
+ * @param {import("geotiff/src/geotiff.js").GeoTIFF|import("geotiff/src/geotiff.js").MultiGeoTIFF} tiff A GeoTIFF.
+ * @return {Promise<Array<import("geotiff/src/geotiffimage.js").GeoTIFFImage>>} Resolves to a list of images.
+ */
+function getImagesForTIFF(tiff) {
+  return tiff.getImageCount().then(function (count) {
+    const requests = new Array(count);
+    for (let i = 0; i < count; ++i) {
+      requests[i] = tiff.getImage(i);
+    }
+    return Promise.all(requests);
+  });
+}
+
+/**
+ * @param {SourceInfo} source The GeoTIFF source.
+ * @return {Promise<Array<import("geotiff/src/geotiffimage.js").GeoTIFFImage>>} Resolves to a list of images.
+ */
+function getImagesForSource(source) {
+  let request;
+  if (source.overviews) {
+    request = tiffFromUrls(source.url, source.overviews);
+  } else {
+    request = tiffFromUrl(source.url);
+  }
+  return request.then(getImagesForTIFF);
+}
+
+/**
+ * @param {number|Array<number>|Array<Array<number>>} expected Expected value.
+ * @param {number|Array<number>|Array<Array<number>>} got Actual value.
+ * @param {string} message The error message.
+ */
+function assertEqual(expected, got, message) {
+  if (Array.isArray(expected)) {
+    const length = expected.length;
+    if (!Array.isArray(got) || length != got.length) {
+      throw new Error(message);
+    }
+    for (let i = 0; i < length; ++i) {
+      assertEqual(expected[i], got[i], message);
+    }
+    return;
+  }
+
+  if (expected !== got) {
+    throw new Error(message);
+  }
+}
+
+/**
+ * @param {Array} array The data array.
+ * @return {number} The minimum value.
+ */
+function getMinForDataType(array) {
+  if (array instanceof Int8Array) {
+    return -128;
+  }
+  if (array instanceof Int16Array) {
+    return -32768;
+  }
+  if (array instanceof Int32Array) {
+    return -2147483648;
+  }
+  if (array instanceof Float32Array) {
+    return 1.2e-38;
+  }
+  return 0;
+}
+
+/**
+ * @param {Array} array The data array.
+ * @return {number} The maximum value.
+ */
+function getMaxForDataType(array) {
+  if (array instanceof Int8Array) {
+    return 127;
+  }
+  if (array instanceof Uint8Array) {
+    return 255;
+  }
+  if (array instanceof Uint8ClampedArray) {
+    return 255;
+  }
+  if (array instanceof Int16Array) {
+    return 32767;
+  }
+  if (array instanceof Uint16Array) {
+    return 65535;
+  }
+  if (array instanceof Int32Array) {
+    return 2147483647;
+  }
+  if (array instanceof Uint32Array) {
+    return 4294967295;
+  }
+  if (array instanceof Float32Array) {
+    return 3.4e38;
+  }
+  return 255;
+}
+
+/**
+ * @typedef Options
+ * @property {Array<SourceInfo>} sources List of information about GeoTIFF sources.
+ */
+
+/**
+ * @classdesc
+ * A source for working with GeoTIFF data.
+ */
+class GeoTIFFSource extends DataTile {
+  /**
+   * @param {Options} options Image tile options.
+   */
+  constructor(options) {
+    super({
+      state: State.LOADING,
+      tileGrid: null,
+      projection: null,
+    });
+
+    /**
+     * @type {Array<SourceInfo>}
+     * @private
+     */
+    this.sourceInfo_ = options.sources;
+
+    const numSources = this.sourceInfo_.length;
+
+    /**
+     * @type {Array<Array<import("geotiff/src/geotiffimage.js").GeoTIFFImage>>}
+     * @private
+     */
+    this.sourceImagery_ = new Array(numSources);
+
+    /**
+     * @type {number}
+     * @private
+     */
+    this.samplesPerPixel_;
+
+    /**
+     * @type {Error}
+     * @private
+     */
+    this.error_ = null;
+
+    const self = this;
+    const requests = new Array(numSources);
+    for (let i = 0; i < numSources; ++i) {
+      requests[i] = getImagesForSource(this.sourceInfo_[i]);
+    }
+    Promise.all(requests)
+      .then(function (sources) {
+        self.configure_(sources);
+      })
+      .catch(function (error) {
+        self.error_ = error;
+        self.setState(State.ERROR);
+      });
+  }
+
+  /**
+   * @return {Error} A source loading error.
+   */
+  getError() {
+    return this.error_;
+  }
+
+  /**
+   * Configure the tile grid based on images within the source GeoTIFFs.  Each GeoTIFF
+   * must have the same internal tiled structure.
+   * @param {Array<Array<import("geotiff/src/geotiffimage.js").GeoTIFFImage>>} sources Each source is a list of images
+   * from a single GeoTIFF.
+   */
+  configure_(sources) {
+    let extent;
+    let origin;
+    let tileSizes;
+    let resolutions;
+    let samplesPerPixel;
+
+    const sourceCount = sources.length;
+    for (let sourceIndex = 0; sourceIndex < sourceCount; ++sourceIndex) {
+      const images = sources[sourceIndex];
+      const imageCount = images.length;
+
+      let sourceExtent;
+      let sourceOrigin;
+      const sourceTileSizes = new Array(imageCount);
+      const sourceResolutions = new Array(imageCount);
+
+      for (let imageIndex = 0; imageIndex < imageCount; ++imageIndex) {
+        const image = images[imageIndex];
+        const imageSamplesPerPixel = image.getSamplesPerPixel();
+        if (!samplesPerPixel) {
+          samplesPerPixel = imageSamplesPerPixel;
+        } else {
+          const message = `Band count mismatch for source ${sourceIndex}, got ${imageSamplesPerPixel} but expected ${samplesPerPixel}`;
+          assertEqual(samplesPerPixel, imageSamplesPerPixel, message);
+        }
+        const level = imageCount - (imageIndex + 1);
+
+        if (!sourceExtent) {
+          sourceExtent = image.getBoundingBox();
+        }
+
+        if (!sourceOrigin) {
+          sourceOrigin = image.getOrigin().slice(0, 2);
+        }
+
+        sourceResolutions[level] = image.getResolution(images[0])[0];
+        sourceTileSizes[level] = [image.getTileWidth(), image.getTileHeight()];
+      }
+
+      if (!extent) {
+        extent = sourceExtent;
+      } else {
+        const message = `Extent mismatch for source ${sourceIndex}, got [${sourceExtent}] but expected [${extent}]`;
+        assertEqual(extent, sourceExtent, message);
+      }
+
+      if (!origin) {
+        origin = sourceOrigin;
+      } else {
+        const message = `Origin mismatch for source ${sourceIndex}, got [${sourceOrigin}] but expected [${origin}]`;
+        assertEqual(origin, sourceOrigin, message);
+      }
+
+      if (!tileSizes) {
+        tileSizes = sourceTileSizes;
+      } else {
+        assertEqual(
+          tileSizes,
+          sourceTileSizes,
+          `Tile size mismatch for source ${sourceIndex}`
+        );
+      }
+
+      if (!resolutions) {
+        resolutions = sourceResolutions;
+      } else {
+        const message = `Resolution mismatch for source ${sourceIndex}, got [${sourceResolutions}] but expected [${resolutions}]`;
+        assertEqual(resolutions, sourceResolutions, message);
+      }
+
+      this.sourceImagery_[sourceIndex] = images.reverse();
+    }
+
+    if (!this.getProjection()) {
+      const firstImage = sources[0][0];
+      if (firstImage.geoKeys) {
+        const code =
+          firstImage.geoKeys.ProjectedCSTypeGeoKey ||
+          firstImage.geoKeys.GeographicTypeGeoKey;
+        if (code) {
+          this.projection = getProjection(`EPSG:${code}`);
+        }
+      }
+    }
+
+    if (sourceCount > 1 && samplesPerPixel !== 1) {
+      throw new Error(
+        'Expected single band GeoTIFFs when using multiple sources'
+      );
+    }
+
+    this.samplesPerPixel_ = samplesPerPixel;
+
+    const tileGrid = new TileGrid({
+      extent: extent,
+      origin: origin,
+      resolutions: resolutions,
+      tileSizes: tileSizes,
+    });
+
+    this.tileGrid = tileGrid;
+
+    this.setLoader(this.loadTile_.bind(this));
+    this.setState(State.READY);
+  }
+
+  loadTile_(z, x, y) {
+    const size = toSize(this.tileGrid.getTileSize(z));
+    const pixelBounds = [
+      x * size[0],
+      y * size[1],
+      (x + 1) * size[0],
+      (y + 1) * size[1],
+    ];
+
+    const sourceCount = this.sourceImagery_.length;
+    const requests = new Array(sourceCount);
+    let addAlpha = false;
+    const sourceInfo = this.sourceInfo_;
+    for (let sourceIndex = 0; sourceIndex < sourceCount; ++sourceIndex) {
+      const image = this.sourceImagery_[sourceIndex][z];
+      requests[sourceIndex] = image.readRasters({window: pixelBounds});
+      if (sourceInfo[sourceIndex].nodata !== undefined) {
+        addAlpha = true;
+      }
+    }
+
+    const samplesPerPixel = this.samplesPerPixel_;
+    let additionalBands = 0;
+    if (addAlpha) {
+      if (sourceCount === 2 && samplesPerPixel === 1) {
+        additionalBands = 2;
+      } else {
+        additionalBands = 1;
+      }
+    }
+    const bandCount = samplesPerPixel * sourceCount + additionalBands;
+    const pixelCount = size[0] * size[1];
+    const dataLength = pixelCount * bandCount;
+
+    return Promise.all(requests).then(function (sourceSamples) {
+      const data = new Uint8ClampedArray(dataLength);
+      for (let pixelIndex = 0; pixelIndex < pixelCount; ++pixelIndex) {
+        let transparent = addAlpha;
+        const sourceOffset = pixelIndex * bandCount;
+        for (let sourceIndex = 0; sourceIndex < sourceCount; ++sourceIndex) {
+          const source = sourceInfo[sourceIndex];
+          let min = source.min;
+          if (min === undefined) {
+            min = getMinForDataType(sourceSamples[sourceIndex][0]);
+          }
+          let max = source.max;
+          if (max === undefined) {
+            max = getMaxForDataType(sourceSamples[sourceIndex][0]);
+          }
+
+          const gain = 255 / (max - min);
+          const bias = -min * gain;
+
+          const nodata = source.nodata;
+
+          const sampleOffset = sourceOffset + sourceIndex * samplesPerPixel;
+          for (
+            let sampleIndex = 0;
+            sampleIndex < samplesPerPixel;
+            ++sampleIndex
+          ) {
+            const sourceValue =
+              sourceSamples[sourceIndex][sampleIndex][pixelIndex];
+
+            const value = gain * sourceValue + bias;
+            if (!addAlpha) {
+              data[sampleOffset + sampleIndex] = value;
+            } else {
+              if (sourceValue !== nodata) {
+                transparent = false;
+                data[sampleOffset + sampleIndex] = value;
+              }
+            }
+          }
+
+          if (addAlpha && !transparent) {
+            data[sampleOffset + samplesPerPixel] = 255;
+          }
+        }
+      }
+
+      return data;
+    });
+  }
+}
+
+export default GeoTIFFSource;

src/ol/style/expressions.js

@@ -170,6 +170,7 @@ export function isTypeUnique(valueType) {
  * @property {Array<string>} variables List of variables used in the expression; contains **unprefixed names**
  * @property {Array<string>} attributes List of attributes used in the expression; contains **unprefixed names**
  * @property {Object<string, number>} stringLiteralsMap This object maps all encountered string values to a number
+ * @property {number} [bandCount] Number of bands per pixel.
  */
 
 /**
@@ -402,6 +403,27 @@ Operators['var'] = {
   },
 };
 
+Operators['band'] = {
+  getReturnType: function (args) {
+    return ValueTypes.NUMBER;
+  },
+  toGlsl: function (context, args) {
+    assertArgsCount(args, 1);
+    const band = args[0];
+    if (typeof band !== 'number') {
+      throw new Error('Band index must be a number');
+    }
+    const zeroBasedBand = band - 1;
+    const colorIndex = Math.floor(zeroBasedBand / 4);
+    let bandIndex = zeroBasedBand % 4;
+    if (band === context.bandCount && bandIndex === 1) {
+      // LUMINANCE_ALPHA - band 1 assigned to rgb and band 2 assigned to alpha
+      bandIndex = 3;
+    }
+    return `color${colorIndex}[${bandIndex}]`;
+  },
+};
+
 Operators['time'] = {
   getReturnType: function (args) {
     return ValueTypes.NUMBER;
@@ -748,17 +770,16 @@ Operators['interpolate'] = {
     assertUniqueInferredType(args, outputType);
 
     const input = expressionToGlsl(context, args[1]);
-    let result = null;
+    const exponent = numberToGlsl(interpolation);
+
+    let result = '';
     for (let i = 2; i < args.length - 2; i += 2) {
       const stop1 = expressionToGlsl(context, args[i]);
-      const output1 = expressionToGlsl(context, args[i + 1], outputType);
+      const output1 =
+        result || expressionToGlsl(context, args[i + 1], outputType);
       const stop2 = expressionToGlsl(context, args[i + 2]);
       const output2 = expressionToGlsl(context, args[i + 3], outputType);
-      result = `mix(${
+      result = `mix(${output1}, ${output2}, pow(clamp((${input} - ${stop1}) / (${stop2} - ${stop1}), 0.0, 1.0), ${exponent}))`;
-        result || output1
-      }, ${output2}, pow(clamp((${input} - ${stop1}) / (${stop2} - ${stop1}), 0.0, 1.0), ${numberToGlsl(
-        interpolation
-      )}))`;
     }
     return result;
   },

src/ol/webgl/TileTexture.js

@@ -0,0 +1,195 @@
+/**
+ * @module ol/webgl/TileTexture
+ */
+
+import EventTarget from '../events/Target.js';
+import EventType from '../events/EventType.js';
+import ImageTile from '../ImageTile.js';
+import TileState from '../TileState.js';
+import WebGLArrayBuffer from './Buffer.js';
+import {ARRAY_BUFFER, STATIC_DRAW} from '../webgl.js';
+import {toSize} from '../size.js';
+
+function bindAndConfigure(gl, texture) {
+  gl.bindTexture(gl.TEXTURE_2D, texture);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+}
+
+/**
+ * @param {WebGLRenderingContext} gl The WebGL context.
+ * @param {WebGLTexture} texture The texture.
+ * @param {HTMLImageElement|HTMLCanvasElement|HTMLVideoElement} image The image.
+ */
+function uploadImageTexture(gl, texture, image) {
+  bindAndConfigure(gl, texture);
+
+  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
+}
+
+/**
+ * @param {WebGLRenderingContext} gl The WebGL context.
+ * @param {WebGLTexture} texture The texture.
+ * @param {import("../DataTile.js").Data} data The pixel data.
+ * @param {import("../size.js").Size} size The pixel size.
+ * @param {number} bandCount The band count.
+ */
+function uploadDataTexture(gl, texture, data, size, bandCount) {
+  bindAndConfigure(gl, texture);
+
+  let format;
+  switch (bandCount) {
+    case 1: {
+      format = gl.LUMINANCE;
+      break;
+    }
+    case 2: {
+      format = gl.LUMINANCE_ALPHA;
+      break;
+    }
+    case 3: {
+      format = gl.RGB;
+      break;
+    }
+    case 4: {
+      format = gl.RGBA;
+      break;
+    }
+    default: {
+      throw new Error(`Unsupported number of bands: ${bandCount}`);
+    }
+  }
+
+  gl.texImage2D(
+    gl.TEXTURE_2D,
+    0,
+    format,
+    size[0],
+    size[1],
+    0,
+    format,
+    gl.UNSIGNED_BYTE,
+    data
+  );
+}
+
+class TileTexture extends EventTarget {
+  /**
+   * @param {import("../DataTile.js").default|import("../ImageTile.js").default} tile The tile.
+   * @param {import("../tilegrid/TileGrid.js").default} grid Tile grid.
+   * @param {import("../webgl/Helper.js").default} helper WebGL helper.
+   */
+  constructor(tile, grid, helper) {
+    super();
+
+    this.tile = tile;
+    this.size = toSize(grid.getTileSize(tile.tileCoord[0]));
+    this.loaded = tile.getState() === TileState.LOADED;
+
+    this.bandCount = NaN;
+
+    this.helper_ = helper;
+    this.handleTileChange_ = this.handleTileChange_.bind(this);
+
+    const coords = new WebGLArrayBuffer(ARRAY_BUFFER, STATIC_DRAW);
+    coords.fromArray([
+      0, // P0
+      1,
+      1, // P1
+      1,
+      1, // P2
+      0,
+      0, // P3
+      0,
+    ]);
+    helper.flushBufferData(coords);
+    this.coords = coords;
+
+    /**
+     * @type {Array<WebGLTexture>}
+     */
+    this.textures = [];
+
+    if (this.loaded) {
+      this.uploadTile_();
+    } else {
+      tile.addEventListener(EventType.CHANGE, this.handleTileChange_);
+    }
+  }
+
+  uploadTile_() {
+    const gl = this.helper_.getGL();
+    const tile = this.tile;
+
+    if (tile instanceof ImageTile) {
+      const texture = gl.createTexture();
+      this.textures.push(texture);
+      this.bandCount = 4;
+      uploadImageTexture(gl, texture, tile.getImage());
+      return;
+    }
+
+    const data = tile.getData();
+    const pixelCount = this.size[0] * this.size[1];
+    this.bandCount = data.byteLength / pixelCount;
+    const textureCount = Math.ceil(this.bandCount / 4);
+
+    if (textureCount === 1) {
+      const texture = gl.createTexture();
+      this.textures.push(texture);
+      uploadDataTexture(gl, texture, data, this.size, this.bandCount);
+      return;
+    }
+
+    const textureDataArrays = new Array(textureCount);
+    for (let textureIndex = 0; textureIndex < textureCount; ++textureIndex) {
+      const texture = gl.createTexture();
+      this.textures.push(texture);
+
+      const bandCount =
+        textureIndex < textureCount - 1 ? 4 : this.bandCount % 4;
+      textureDataArrays[textureIndex] = new Uint8Array(pixelCount * bandCount);
+    }
+
+    const valueCount = pixelCount * this.bandCount;
+    for (let dataIndex = 0; dataIndex < valueCount; ++dataIndex) {
+      const bandIndex = dataIndex % this.bandCount;
+      const textureBandIndex = bandIndex % 4;
+      const textureIndex = Math.floor(bandIndex / 4);
+      const bandCount =
+        textureIndex < textureCount - 1 ? 4 : this.bandCount % 4;
+      const pixelIndex = Math.floor(dataIndex / this.bandCount);
+      textureDataArrays[textureIndex][
+        pixelIndex * bandCount + textureBandIndex
+      ] = data[dataIndex];
+    }
+
+    for (let textureIndex = 0; textureIndex < textureCount; ++textureIndex) {
+      const bandCount =
+        textureIndex < textureCount - 1 ? 4 : this.bandCount % 4;
+      const texture = this.textures[textureIndex];
+      const data = textureDataArrays[textureIndex];
+      uploadDataTexture(gl, texture, data, this.size, bandCount);
+    }
+  }
+
+  handleTileChange_() {
+    if (this.tile.getState() === TileState.LOADED) {
+      this.loaded = true;
+      this.uploadTile_();
+      this.dispatchEvent(EventType.CHANGE);
+    }
+  }
+
+  disposeInternal() {
+    const gl = this.helper_.getGL();
+    this.helper_.deleteBuffer(this.coords);
+    for (let i = 0; i < this.textures.length; ++i) {
+      gl.deleteTexture(this.textures[i]);
+    }
+    this.tile.removeEventListener(EventType.CHANGE, this.handleTileChange_);
+  }
+}
+
+export default TileTexture;