Workaround for raster source

examples/sea-level.js

@@ -2,7 +2,7 @@ import Map from '../src/ol/Map.js';
 import View from '../src/ol/View.js';
 import {Image as ImageLayer, Tile as TileLayer} from '../src/ol/layer.js';
 import {fromLonLat} from '../src/ol/proj.js';
-import RasterSource from '../src/ol/source/Raster.js';
+import {Raster as RasterSource, TileJSON} from '../src/ol/source.js';
 import XYZ from '../src/ol/source/XYZ.js';
 
 function flood(pixels, data) {
@@ -37,8 +37,9 @@ const map = new Map({
   target: 'map',
   layers: [
     new TileLayer({
-      source: new XYZ({
+      source: new TileJSON({
-        url: 'https://api.mapbox.com/styles/v1/tschaub/ciutc102t00c62js5fqd47kqw/tiles/256/{z}/{x}/{y}?access_token=' + key
+        url: 'https://api.tiles.mapbox.com/v3/mapbox.world-light.json?secure',
+        crossOrigin: 'anonymous'
       })
     }),
     new ImageLayer({

src/ol/source/Raster.js

@@ -441,6 +441,15 @@ function getImageData(renderer, frameState, layerState) {
   }
   const width = frameState.size[0];
   const height = frameState.size[1];
+  const element = renderer.renderFrame(frameState, layerState);
+  if (!(element instanceof HTMLCanvasElement)) {
+    throw new Error('Unsupported rendered element: ' + element);
+  }
+  if (element.width === width && element.height === height) {
+    const context = element.getContext('2d');
+    return context.getImageData(0, 0, width, height);
+  }
+
   if (!sharedContext) {
     sharedContext = createCanvasContext2D(width, height);
   } else {
@@ -451,7 +460,7 @@ function getImageData(renderer, frameState, layerState) {
       sharedContext.clearRect(0, 0, width, height);
     }
   }
-  renderer.composeFrame(frameState, layerState, sharedContext);
+  sharedContext.drawImage(element, 0, 0, width, height);
   return sharedContext.getImageData(0, 0, width, height);
 }