# ImageryProvider

#### abstract new Cesium.ImageryProvider()
Scene/ImageryProvider.js 34

Provides imagery to be displayed on the surface of an ellipsoid. This type describes an interface and is not intended to be instantiated directly.

##### Demo:

- Cesium Sandcastle Imagery Layers Demo
- Cesium Sandcastle Imagery Manipulation Demo

##### See:

- ArcGisMapServerImageryProvider
- BingMapsImageryProvider
- OpenStreetMapImageryProvider
- TileMapServiceImageryProvider
- GoogleEarthEnterpriseImageryProvider
- GoogleEarthEnterpriseMapsProvider
- GridImageryProvider
- IonImageryProvider
- MapboxImageryProvider
- MapboxStyleImageryProvider
- SingleTileImageryProvider
- TileCoordinatesImageryProvider
- UrlTemplateImageryProvider
- WebMapServiceImageryProvider
- WebMapTileServiceImageryProvider

### Members

#### readonly credit : Credit
Scene/ImageryProvider.js 248

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 `ImageryProvider#ready` returns true.

#### defaultAlpha : Number|undefined
Scene/ImageryProvider.js 42

The default alpha blending value of this provider, with 0.0 representing fully transparent and 1.0 representing fully opaque.

Default Value: `undefined`

#### defaultBrightness : Number|undefined
Scene/ImageryProvider.js 69

The default brightness of this provider. 1.0 uses the unmodified imagery color. Less than 1.0 makes the imagery darker while greater than 1.0 makes it brighter.

Default Value: `undefined`

#### defaultContrast : Number|undefined
Scene/ImageryProvider.js 78

The default contrast of this provider. 1.0 uses the unmodified imagery color. Less than 1.0 reduces the contrast while greater than 1.0 increases it.

Default Value: `undefined`

#### defaultDayAlpha : Number|undefined
Scene/ImageryProvider.js 60

The default alpha blending value on the day side of the globe of this provider, with 0.0 representing fully transparent and 1.0 representing fully opaque.

Default Value: `undefined`

#### defaultGamma : Number|undefined
Scene/ImageryProvider.js 103

The default gamma correction to apply to this provider. 1.0 uses the unmodified imagery color.

Default Value: `undefined`

#### defaultHue : Number|undefined
Scene/ImageryProvider.js 86

The default hue of this provider in radians. 0.0 uses the unmodified imagery color.

Default Value: `undefined`

#### defaultMagnificationFilter : TextureMagnificationFilter
Scene/ImageryProvider.js 119

The default texture magnification filter to apply to this provider.

Default Value: `undefined`

#### defaultMinificationFilter : TextureMinificationFilter
Scene/ImageryProvider.js 111

The default texture minification filter to apply to this provider.

Default Value: `undefined`

#### defaultNightAlpha : Number|undefined
Scene/ImageryProvider.js 51

The default alpha blending value on the night side of the globe of this provider, with 0.0 representing fully transparent and 1.0 representing fully opaque.

Default Value: `undefined`

#### defaultSaturation : Number|undefined
Scene/ImageryProvider.js 95

The default saturation of this provider. 1.0 uses the unmodified imagery color. Less than 1.0 reduces the saturation while greater than 1.0 increases it.

Default Value: `undefined`

#### readonly errorEvent : Event
Scene/ImageryProvider.js 236

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 `TileProviderError`.

#### readonly hasAlphaChannel : Boolean
Scene/ImageryProvider.js 272

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.

#### isStretchImage : String|undefined
Scene/ImageryProvider.js 284

超过最大最小层级范围图像是否进行图像的拉伸。此值未定义或者设置为true时,如果图像level小于minimumLevel或者大于maximumLevel，图像会进行拉伸。反之，如果图像level小于minimumLevel或者大于maximumLevel，不会再请求图像以及拉伸图像。

#### readonly maximumLevel : Number|undefined
Scene/ImageryProvider.js 185

Gets the maximum level-of-detail that can be requested. This function should not be called before `ImageryProvider#ready` returns true.

#### readonly minimumLevel : Number
Scene/ImageryProvider.js 200

Gets the minimum level-of-detail that can be requested. This function should not be called before `ImageryProvider#ready` returns true. Generally, a minimum level should only be used when the rectangle of the imagery is small enough that the number of tiles at the minimum level is small. An imagery provider with more than a few tiles at the minimum level will lead to rendering problems.

#### readonly proxy : Proxy
Scene/ImageryProvider.js 258

Gets the proxy used by this provider.

#### readonly ready : Boolean
Scene/ImageryProvider.js 131

Gets a value indicating whether or not the provider is ready for use.

#### readonly readyPromise : Promise.<Boolean>
Scene/ImageryProvider.js 141

Gets a promise that resolves to true when the provider is ready for use.

#### readonly rectangle : Rectangle
Scene/ImageryProvider.js 152

Gets the rectangle, in radians, of the imagery provided by the instance. This function should not be called before `ImageryProvider#ready` returns true.

#### readonly tileDiscardPolicy : TileDiscardPolicy
Scene/ImageryProvider.js 224

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 `ImageryProvider#ready` returns true.

#### readonly tileHeight : Number
Scene/ImageryProvider.js 174

Gets the height of each tile, in pixels. This function should not be called before `ImageryProvider#ready` returns true.

#### readonly tileWidth : Number
Scene/ImageryProvider.js 163

Gets the width of each tile, in pixels. This function should not be called before `ImageryProvider#ready` returns true.

#### readonly tilingScheme : TilingScheme
Scene/ImageryProvider.js 211

Gets the tiling scheme used by the provider. This function should not be called before `ImageryProvider#ready` returns true.

### Methods

#### static Cesium.ImageryProvider.loadImage(imageryProvider, url) → Promise.<(HTMLImageElement|HTMLCanvasElement)>|undefined
Scene/ImageryProvider.js 359

Loads an image from a given URL. If the server referenced by the URL already has too many requests pending, this function will instead return undefined, indicating that the request should be retried later.

Name | Type | Description
--- | --- | ---
`imageryProvider` | ImageryProvider | The imagery provider for the URL.
`url` | Resource | String | The URL of the image.

##### Returns:

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.

#### getTileCredits(x, y, level) → Array.<Credit>
Scene/ImageryProvider.js 299

Gets the credits to be displayed when a given tile is displayed.

Name | Type | Description
--- | --- | ---
`x` | Number | The tile X coordinate.
`y` | Number | The tile Y coordinate.
`level` | Number | The tile level;

##### Returns:

The credits to be displayed when the tile is displayed.

##### Throws:

- DeveloperError : `getTileCredits` must not be called before the imagery provider is ready.

#### pickFeatures(x, y, level, longitude, latitude) → Promise.<Array.<ImageryLayerFeatureInfo>>|undefined
Scene/ImageryProvider.js 341

Asynchronously determines what features, if any, are located at a given longitude and latitude within a tile. This function should not be called before `ImageryProvider#ready` returns true. This function is optional, so it may not exist on all ImageryProviders.

Name | Type | Description
--- | --- | ---
`x` | Number | The tile X coordinate.
`y` | Number | The tile Y coordinate.
`level` | Number | The tile level.
`longitude` | Number | The longitude at which to pick features.
`latitude` | Number | The latitude at which to pick features.

##### Returns:

A promise for the picked features that will resolve when the asynchronous picking completes. The resolved value is an array of `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.

##### Throws:

- DeveloperError : `pickFeatures` must not be called before the imagery provider is ready.

#### requestImage(x, y, level, request) → Promise.<(HTMLImageElement|HTMLCanvasElement)>|undefined
Scene/ImageryProvider.js 318

Requests the image for a given tile. This function should not be called before `ImageryProvider#ready` returns true.

Name | Type | Description
--- | --- | ---
`x` | Number | The tile X coordinate.
`y` | Number | The tile Y coordinate.
`level` | Number | The tile level.
`request` | Request | optional The request object. Intended for internal use only.

##### Returns:

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.

##### Throws:

- DeveloperError : `requestImage` must not be called before the imagery provider is ready.