Merge pull request #41 from TerriaJS/bing-aerial-with-labels-on-demand

added support for Bing Maps' AerialWithLabelsOnDemand imagery set, as…

Source/Core/Resource.js

@@ -953,6 +953,8 @@ define([
                     window.URL.revokeObjectURL(generatedBlobResource.url);
                 }
 
+                error.blob = generatedBlob;
+
                 return when.reject(error);
             });
     };

Source/Scene/BingMapsImageryProvider.js

@@ -18,6 +18,7 @@ define([
         '../ThirdParty/when',
         './BingMapsStyle',
         './DiscardMissingTileImagePolicy',
+        './DiscardEmptyTileImagePolicy',
         './ImageryProvider'
     ], function(
         BingMapsApi,
@@ -39,6 +40,7 @@ define([
         when,
         BingMapsStyle,
         DiscardMissingTileImagePolicy,
+        DiscardEmptyTilePolicy,
         ImageryProvider) {
     'use strict';
 
@@ -61,15 +63,16 @@ define([
      *        for information on the supported cultures.
      * @param {Ellipsoid} [options.ellipsoid] The ellipsoid.  If not specified, the WGS84 ellipsoid is used.
      * @param {TileDiscardPolicy} [options.tileDiscardPolicy] The policy that determines if a tile
-     *        is invalid and should be discarded.  If this value is not specified, a default
-     *        {@link DiscardMissingTileImagePolicy} is used which requests
-     *        tile 0,0 at the maximum tile level and checks pixels (0,0), (120,140), (130,160),
-     *        (200,50), and (200,200).  If all of these pixels are transparent, the discard check is
-     *        disabled and no tiles are discarded.  If any of them have a non-transparent color, any
-     *        tile that has the same values in these pixel locations is discarded.  The end result of
-     *        these defaults should be correct tile discarding for a standard Bing Maps server.  To ensure
-     *        that no tiles are discarded, construct and pass a {@link NeverTileDiscardPolicy} for this
-     *        parameter.
+     *        is invalid and should be discarded.  The default value will depend on the map style.  If
+     *        `BingMapsStyle.AERIAL_WITH_LABELS_ON_DEMAND` or `BingMapsStyle.ROADS_ON_DEMAND` is used, then a
+     *        {@link DiscardEmptyTileImagePolicy} will be used to handle the Bing Maps API sending no content instead of
+     *        a missing tile image, a behaviour specific to that imagery set.  In all over cases, a default
+     *        {@link DiscardMissingTileImagePolicy} is used which requests tile 0,0 at the maximum tile level and checks
+     *        pixels (0,0), (120,140), (130,160), (200,50), and (200,200).  If all of these pixels are transparent, the
+     *        discard check is disabled and no tiles are discarded.  If any of them have a non-transparent color, any
+     *        tile that has the same values in these pixel locations is discarded.  The end result of these defaults
+     *        should be correct tile discarding for a standard Bing Maps server.  To ensure that no tiles are discarded,
+     *        construct and pass a {@link NeverTileDiscardPolicy} for this parameter.
      *
      * @see ArcGisMapServerImageryProvider
      * @see GoogleEarthEnterpriseMapsProvider
@@ -171,11 +174,18 @@ define([
 
             // Install the default tile discard policy if none has been supplied.
             if (!defined(that._tileDiscardPolicy)) {
-                that._tileDiscardPolicy = new DiscardMissingTileImagePolicy({
-                    missingImageUrl : buildImageResource(that, 0, 0, that._maximumLevel).url,
-                    pixelsToCheck : [new Cartesian2(0, 0), new Cartesian2(120, 140), new Cartesian2(130, 160), new Cartesian2(200, 50), new Cartesian2(200, 200)],
-                    disableCheckIfAllPixelsAreTransparent : true
-                });
+                // Our default depends on which map style we're using.
+                if (that._mapStyle === BingMapsStyle.AERIAL_WITH_LABELS_ON_DEMAND
+                    || that._mapStyle === BingMapsStyle.ROAD_ON_DEMAND) {
+                    // this map style uses a different API, which returns a tile with no data instead of a placeholder image
+                    that._tileDiscardPolicy = new DiscardEmptyTilePolicy();
+                } else {
+                    that._tileDiscardPolicy = new DiscardMissingTileImagePolicy({
+                        missingImageUrl : buildImageResource(that, 0, 0, that._maximumLevel).url,
+                        pixelsToCheck : [new Cartesian2(0, 0), new Cartesian2(120, 140), new Cartesian2(130, 160), new Cartesian2(200, 50), new Cartesian2(200, 200)],
+                        disableCheckIfAllPixelsAreTransparent : true
+                    });
+                }
             }
 
             var attributionList = that._attributionList = resource.imageryProviders;
@@ -533,7 +543,23 @@ define([
         }
         //>>includeEnd('debug');
 
-        return ImageryProvider.loadImage(this, buildImageResource(this, x, y, level, request));
+        var promise = ImageryProvider.loadImage(this, buildImageResource(this, x, y, level, request));
+
+        if (defined(promise)) {
+            return promise.otherwise(function(error) {
+
+                // One possible cause of an error here is that the image we tried to load was empty. This isn't actually
+                // a problem. In some imagery sets (eg. `BingMapsStyle.AERIAL_WITH_LABELS_ON_DEMAND`), an empty image is
+                // returned rather than a blank "This Image is Missing" placeholder image. In this case, we supress the
+                // error.
+                if (defined(error.blob) && error.blob.size === 0) {
+                    return DiscardEmptyTilePolicy.EMPTY_IMAGE;
+                }
+                return when.reject(error);
+            });
+        }
+
+        return undefined;
     };
 
     /**

Source/Scene/BingMapsStyle.js

@@ -25,17 +25,37 @@ define([
          *
          * @type {String}
          * @constant
+         * @deprecated See https://github.com/AnalyticalGraphicsInc/cesium/issues/7128.
+         * Use `BingMapsStyle.AERIAL_WITH_LABELS_ON_DEMAND` instead
          */
         AERIAL_WITH_LABELS : 'AerialWithLabels',
 
+        /**
+         * Aerial imagery with a road overlay.
+         *
+         * @type {String}
+         * @constant
+         */
+        AERIAL_WITH_LABELS_ON_DEMAND : 'AerialWithLabelsOnDemand',
+
         /**
          * Roads without additional imagery.
          *
          * @type {String}
          * @constant
+         * @deprecated See https://github.com/AnalyticalGraphicsInc/cesium/issues/7128.
+         * Use `BingMapsStyle.ROAD_ON_DEMAND` instead
          */
         ROAD : 'Road',
 
+        /**
+         * Roads without additional imagery.
+         *
+         * @type {String}
+         * @constant
+         */
+        ROAD_ON_DEMAND : 'RoadOnDemand',
+
         /**
          * A dark version of the road maps.
          *

Source/Scene/DiscardEmptyTileImagePolicy.js

@@ -0,0 +1,43 @@
+define([
+    '../Core/defined',
+    '../Core/defaultValue'
+], function(
+    defined,
+    defaultValue) {
+
+    /**
+     * A policy for discarding tile images that contain no data (and so aren't actually images).
+     *
+     * @alias DiscardEmptyTileImagePolicy
+     * @constructor
+     *
+     * @see DiscardMissingTileImagePolicy
+     */
+    function DiscardEmptyTileImagePolicy(options) {
+    }
+
+    /**
+     * Determines if the discard policy is ready to process images.
+     * @returns {Boolean} True if the discard policy is ready to process images; otherwise, false.
+     */
+    DiscardEmptyTileImagePolicy.prototype.isReady = function() {
+        return true;
+    };
+
+    /**
+     * Given a tile image, decide whether to discard that image.
+     *
+     * @param {Image} image An image to test.
+     * @returns {Boolean} True if the image should be discarded; otherwise, false.
+     */
+    DiscardEmptyTileImagePolicy.prototype.shouldDiscardImage = function(image) {
+        return DiscardEmptyTileImagePolicy.EMPTY_IMAGE === image;
+    };
+
+    /**
+     * Default value for representing an empty image.
+     */
+    DiscardEmptyTileImagePolicy.EMPTY_IMAGE = {};
+
+    return DiscardEmptyTileImagePolicy;
+});