text: define([
          '../Core/Credit',
          '../Core/defaultValue',
          '../Core/defined',
          '../Core/defineProperties',
          '../Core/deprecationWarning',
          '../Core/DeveloperError',
          '../Core/Event',
          '../Core/GeographicTilingScheme',
          '../Core/Rectangle',
          '../Core/Resource',
          '../Core/RuntimeError',
          '../Core/TileProviderError',
          '../ThirdParty/when'
      ], function(
          Credit,
          defaultValue,
          defined,
          defineProperties,
          deprecationWarning,
          DeveloperError,
          Event,
          GeographicTilingScheme,
          Rectangle,
          Resource,
          RuntimeError,
          TileProviderError,
          when) {
      'use strict';
  
      /**
       * Provides a single, top-level imagery tile.  The single image is assumed to use a
       * {@link GeographicTilingScheme}.
       *
       * @alias SingleTileImageryProvider
       * @constructor
       *
       * @param {Object} options Object with the following properties:
       * @param {Resource|String} options.url The url for the tile.
       * @param {Rectangle} [options.rectangle=Rectangle.MAX_VALUE] The rectangle, in radians, covered by the image.
       * @param {Credit|String} [options.credit] A credit for the data source, which is displayed on the canvas.
       * @param {Ellipsoid} [options.ellipsoid] The ellipsoid.  If not specified, the WGS84 ellipsoid is used.
       *
       * @see ArcGisMapServerImageryProvider
       * @see BingMapsImageryProvider
       * @see GoogleEarthEnterpriseMapsProvider
       * @see createOpenStreetMapImageryProvider
       * @see createTileMapServiceImageryProvider
       * @see WebMapServiceImageryProvider
       * @see WebMapTileServiceImageryProvider
       * @see UrlTemplateImageryProvider
       */
      function SingleTileImageryProvider(options) {
          options = defaultValue(options, {});
          //>>includeStart('debug', pragmas.debug);
          if (!defined(options.url)) {
              throw new DeveloperError('options.url is required.');
          }
          //>>includeEnd('debug');
  
          if (defined(options.proxy)) {
              deprecationWarning('SingleTileImageryProvider.proxy', 'The options.proxy parameter has been deprecated. Specify options.url as a Resource instance and set the proxy property there.');
          }
  
          var resource = Resource.createIfNeeded(options.url, {
              proxy: options.proxy
          });
  
          var rectangle = defaultValue(options.rectangle, Rectangle.MAX_VALUE);
          var tilingScheme = new GeographicTilingScheme({
              rectangle : rectangle,
              numberOfLevelZeroTilesX : 1,
              numberOfLevelZeroTilesY : 1,
              ellipsoid : options.ellipsoid
          });
          this._tilingScheme = tilingScheme;
          this._resource = resource;
          this._image = undefined;
          this._texture = undefined;
          this._tileWidth = 0;
          this._tileHeight = 0;
  
          this._errorEvent = new Event();
  
          this._ready = false;
          this._readyPromise = when.defer();
  
          var credit = options.credit;
          if (typeof credit === 'string') {
              credit = new Credit({text: credit});
          }
          this._credit = credit;
  
          var that = this;
          var error;
  
          function success(image) {
              that._image = image;
              that._tileWidth = image.width;
              that._tileHeight = image.height;
              that._ready = true;
              that._readyPromise.resolve(true);
              TileProviderError.handleSuccess(that._errorEvent);
          }
  
          function failure(e) {
              var message = 'Failed to load image ' + resource.url + '.';
              error = TileProviderError.handleError(
                      error,
                      that,
                      that._errorEvent,
                      message,
                      0, 0, 0,
                      doRequest,
                      e);
              that._readyPromise.reject(new RuntimeError(message));
          }
  
          function doRequest() {
              when(resource.fetchImage(), success, failure);
          }
  
          doRequest();
      }
  
      defineProperties(SingleTileImageryProvider.prototype, {
          /**
           * Gets the URL of the single, top-level imagery tile.
           * @memberof SingleTileImageryProvider.prototype
           * @type {String}
           * @readonly
           */
          url : {
              get : function() {
                  return this._resource.url;
              }
          },
  
          /**
           * Gets the proxy used by this provider.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Proxy}
           * @readonly
           */
          proxy : {
              get : function() {
                  return this._resource.proxy;
              }
          },
  
          /**
           * Gets the width of each tile, in pixels. This function should
           * not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Number}
           * @readonly
           */
          tileWidth : {
              get : function() {
                  //>>includeStart('debug', pragmas.debug);
                  if (!this._ready) {
                      throw new DeveloperError('tileWidth must not be called before the imagery provider is ready.');
                  }
                  //>>includeEnd('debug');
  
                  return this._tileWidth;
              }
          },
  
          /**
           * Gets the height of each tile, in pixels.  This function should
           * not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Number}
           * @readonly
           */
          tileHeight: {
              get : function() {
                  //>>includeStart('debug', pragmas.debug);
                  if (!this._ready) {
                      throw new DeveloperError('tileHeight must not be called before the imagery provider is ready.');
                  }
                  //>>includeEnd('debug');
  
                  return this._tileHeight;
              }
          },
  
          /**
           * Gets the maximum level-of-detail that can be requested.  This function should
           * not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Number}
           * @readonly
           */
          maximumLevel : {
              get : function() {
                  //>>includeStart('debug', pragmas.debug);
                  if (!this._ready) {
                      throw new DeveloperError('maximumLevel must not be called before the imagery provider is ready.');
                  }
                  //>>includeEnd('debug');
  
                  return 0;
              }
          },
  
          /**
           * Gets the minimum level-of-detail that can be requested.  This function should
           * not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Number}
           * @readonly
           */
          minimumLevel : {
              get : function() {
                  //>>includeStart('debug', pragmas.debug);
                  if (!this._ready) {
                      throw new DeveloperError('minimumLevel must not be called before the imagery provider is ready.');
                  }
                  //>>includeEnd('debug');
  
                  return 0;
              }
          },
  
          /**
           * Gets the tiling scheme used by this provider.  This function should
           * not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {TilingScheme}
           * @readonly
           */
          tilingScheme : {
              get : function() {
                  //>>includeStart('debug', pragmas.debug);
                  if (!this._ready) {
                      throw new DeveloperError('tilingScheme must not be called before the imagery provider is ready.');
                  }
                  //>>includeEnd('debug');
  
                  return this._tilingScheme;
              }
          },
  
          /**
           * Gets the rectangle, in radians, of the imagery provided by this instance.  This function should
           * not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Rectangle}
           * @readonly
           */
          rectangle : {
              get : function() {
                  return this._tilingScheme.rectangle;
              }
          },
  
          /**
           * Gets the tile discard policy.  If not undefined, the discard policy is responsible
           * for filtering out "missing" tiles via its shouldDiscardImage function.  If this function
           * returns undefined, no tiles are filtered.  This function should
           * not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {TileDiscardPolicy}
           * @readonly
           */
          tileDiscardPolicy : {
              get : function() {
                  //>>includeStart('debug', pragmas.debug);
                  if (!this._ready) {
                      throw new DeveloperError('tileDiscardPolicy must not be called before the imagery provider is ready.');
                  }
                  //>>includeEnd('debug');
  
                  return undefined;
              }
          },
  
          /**
           * Gets an event that is raised when the imagery provider encounters an asynchronous error.  By subscribing
           * to the event, you will be notified of the error and can potentially recover from it.  Event listeners
           * are passed an instance of {@link TileProviderError}.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Event}
           * @readonly
           */
          errorEvent : {
              get : function() {
                  return this._errorEvent;
              }
          },
  
          /**
           * Gets a value indicating whether or not the provider is ready for use.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Boolean}
           * @readonly
           */
          ready : {
              get : function() {
                  return this._ready;
              }
          },
  
          /**
           * Gets a promise that resolves to true when the provider is ready for use.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Promise.<Boolean>}
           * @readonly
           */
          readyPromise : {
              get : function() {
                  return this._readyPromise.promise;
              }
          },
  
          /**
           * Gets the credit to display when this imagery provider is active.  Typically this is used to credit
           * the source of the imagery.  This function should not be called before {@link SingleTileImageryProvider#ready} returns true.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Credit}
           * @readonly
           */
          credit : {
              get : function() {
                  return this._credit;
              }
          },
  
          /**
           * Gets a value indicating whether or not the images provided by this imagery provider
           * include an alpha channel.  If this property is false, an alpha channel, if present, will
           * be ignored.  If this property is true, any images without an alpha channel will be treated
           * as if their alpha is 1.0 everywhere.  When this property is false, memory usage
           * and texture upload time are reduced.
           * @memberof SingleTileImageryProvider.prototype
           * @type {Boolean}
           * @readonly
           */
          hasAlphaChannel : {
              get : function() {
                  return true;
              }
          }
      });
  
      /**
       * Gets the credits to be displayed when a given tile is displayed.
       *
       * @param {Number} x The tile X coordinate.
       * @param {Number} y The tile Y coordinate.
       * @param {Number} level The tile level;
       * @returns {Credit[]} The credits to be displayed when the tile is displayed.
       *
       * @exception {DeveloperError} <code>getTileCredits</code> must not be called before the imagery provider is ready.
       */
      SingleTileImageryProvider.prototype.getTileCredits = function(x, y, level) {
          return undefined;
      };
  
      /**
       * Requests the image for a given tile.  This function should
       * not be called before {@link SingleTileImageryProvider#ready} returns true.
       *
       * @param {Number} x The tile X coordinate.
       * @param {Number} y The tile Y coordinate.
       * @param {Number} level The tile level.
       * @param {Request} [request] The request object. Intended for internal use only.
       * @returns {Promise.<Image|Canvas>|undefined} A promise for the image that will resolve when the image is available, or
       *          undefined if there are too many active requests to the server, and the request
       *          should be retried later.  The resolved image may be either an
       *          Image or a Canvas DOM object.
       *
       * @exception {DeveloperError} <code>requestImage</code> must not be called before the imagery provider is ready.
       */
      SingleTileImageryProvider.prototype.requestImage = function(x, y, level, request) {
          //>>includeStart('debug', pragmas.debug);
          if (!this._ready) {
              throw new DeveloperError('requestImage must not be called before the imagery provider is ready.');
          }
          //>>includeEnd('debug');
  
          return this._image;
      };
  
      /**
       * Picking features is not currently supported by this imagery provider, so this function simply returns
       * undefined.
       *
       * @param {Number} x The tile X coordinate.
       * @param {Number} y The tile Y coordinate.
       * @param {Number} level The tile level.
       * @param {Number} longitude The longitude at which to pick features.
       * @param {Number} latitude  The latitude at which to pick features.
       * @return {Promise.<ImageryLayerFeatureInfo[]>|undefined} A promise for the picked features that will resolve when the asynchronous
       *                   picking completes.  The resolved value is an array of {@link ImageryLayerFeatureInfo}
       *                   instances.  The array may be empty if no features are found at the given location.
       *                   It may also be undefined if picking is not supported.
       */
      SingleTileImageryProvider.prototype.pickFeatures = function(x, y, level, longitude, latitude) {
          return undefined;
      };
  
      return SingleTileImageryProvider;
  });
  