OpenLayers源码解析8 ol/source/TileWMS.js

ol/source/TileWMS.js

父类

ol/source/TileImage-TileImage

主要功能

WMS服务提供的底图图层源。

参数：TileWMS({})

参数	类型	说明
params	Object.<string, *>	至少需要LAYER参数。 STYLE默认是’' VERSION默认是‘1.3.0’ WIDTH，HEIGHT，BBOX，CRS会被动态设定
hidpi	boolean (defaults to true)	使用ol/Map#pixelRatio值请求数据
serverType	module:ol/source/WMSServerType string	WMS服务的类型，当hidpi参数设置为true时才有效
url	string	WMS服务地址
transition	number	渲染时不透明度转换的持续时间，要禁用不透明度转换，使用transition：0

方法

/**
 * @module ol/source/TileWMS
 */

import {
   DEFAULT_WMS_VERSION} from './common.js';

import TileImage from './TileImage.js';
import WMSServerType from './WMSServerType.js';
import {
   appendParams} from '../uri.js';
import {
   assert} from '../asserts.js';
import {
   assign} from '../obj.js';
import {
   buffer, createEmpty} from '../extent.js';
import {
   buffer as bufferSize, scale as scaleSize, toSize} from '../size.js';
import {
   calculateSourceResolution} from '../reproj.js';
import {
   compareVersions} from '../string.js';
import {
   get as getProjection, transform, transformExtent} from '../proj.js';
import {
   modulo} from '../math.js';
import {
   hash as tileCoordHash} from '../tilecoord.js';

/**
 * @typedef {Object} Options
 * @property {import("./Source.js").AttributionLike} [attributions] Attributions.
 * @property {boolean} [attributionsCollapsible=true] Attributions are collapsible.
 * @property {number} [cacheSize] Initial tile cache size. Will auto-grow to hold at least the number of tiles in the viewport.
 * @property {null|string} [crossOrigin] The `crossOrigin` attribute for loaded images.  Note that
 * you must provide a `crossOrigin` value if you want to access pixel data with the Canvas renderer.
 * See https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_enabled_image for more detail.
 * @property {boolean} [imageSmoothing=true] Enable image smoothing.
 * @property {Object<string,*>} params WMS request parameters.
 * At least a `LAYERS` param is required. `STYLES` is
 * `''` by default. `VERSION` is `1.3.0` by default. `WIDTH`, `HEIGHT`, `BBOX`
 * and `CRS` (`SRS` for WMS version < 1.3.0) will be set dynamically.
 * @property {number} [gutter=0]
 * The size in pixels of the gutter around image tiles to ignore. By setting
 * this property to a non-zero value, images will be requested that are wider
 * and taller than the tile size by a value of `2 x gutter`.
 * Using a non-zero value allows artifacts of rendering at tile edges to be
 * ignored. If you control the WMS service it is recommended to address
 * "artifacts at tile edges" issues by properly configuring the WMS service. For
 * example, MapServer has a `tile_map_edge_buffer` configuration parameter for
 * this. See https://mapserver.org/output/tile_mode.html.
 * @property {boolean} [hidpi=true] Use the `ol/Map#pixelRatio` value when requesting
 * the image from the remote server.
 * @property {import("../proj.js").ProjectionLike} [projection] Projection. Default is the view projection.
 * @property {number} [reprojectionErrorThreshold=0.5] Maximum allowed reprojection error (in pixels).
 * Higher values can increase reprojection performance, but decrease precision.
 * @property {typeof import("../ImageTile.js").default} [tileClass] Class used to instantiate image tiles.
 * Default is {@link module:ol/ImageTile~ImageTile}.
 * @property {import("../tilegrid/TileGrid.js").default} [tileGrid] Tile grid. Base this on the resolutions,
 * tilesize and extent supported by the server.
 * If this is not defined, a default grid will be used: if there is a projection
 * extent, the grid will be based on that; if not, a grid based on a global
 * extent with origin at 0,0 will be used..
 * @property {import("./WMSServerType.js").default|string} [serverType]
 * The type of the remote WMS server. Currently only used when `hidpi` is
 * `true`.
 * @property {import("../Tile.js").LoadFunction} [tileLoadFunction] Optional function to load a tile given a URL. The default is
 * ```js
 * function(imageTile, src) {
 *   imageTile.getImage().src = src;
 * };
 * ```
 * @property {string} [url] WMS service URL.
 * @property {Array<string>} [urls] WMS service urls.
 * Use this instead of `url` when the WMS supports multiple urls for GetMap requests.
 * @property {boolean} [wrapX=true] Whether to wrap the world horizontally.
 * When set to `false`, only one world
 * will be rendered. When `true`, tiles will be requested for one world only,
 * but they will be wrapped horizontally to render multiple worlds.
 * @property {number} [transition] Duration of the opacity transition for rendering.
 * To disable the opacity transition, pass `transition: 0`.
 * @property {number|import("../array.js").NearestDirectionFunction} [zDirection=0]
 * Choose whether to use tiles with a higher or lower zoom level when between integer
 * zoom levels. See {@link module:ol/tilegrid/TileGrid~TileGrid#getZForResolution}.
 */

/**
 * @classdesc
 * Layer source for tile data from WMS servers.
 * @api
 */
class TileWMS extends TileImage {
   
  /**
   * @param {Options} [opt_options] Tile WMS options.
   */
  constructor(opt_options) {
   
    const options = opt_options ? opt_options : /** @type {Options} */ ({
   });

    const params = options.params || {
   };

    const transparent = 'TRANSPARENT' in params ? params['TRANSPARENT'] : true;

    super({
   
      attributions: options.attributions,
      attributionsCollapsible: options.attributionsCollapsible,
      cacheSize: options.cacheSize,
      crossOrigin: options.crossOrigin,
      imageSmoothing: options.imageSmoothing,
      opaque: !transparent,
      projection: options.projection,
      reprojectionErrorThreshold: options.reprojectionErrorThreshold,
      tileClass: options.tileClass,
      tileGrid: options.tileGrid,
      tileLoadFunction: options.tileLoadFunction,
      url: options.url,
      urls: options.urls,
      wrapX: options.wrapX !== undefined