Projection.js

/**
 * @module ol/proj/Projection
 */
import {METERS_PER_UNIT} from './Units.js';

/**
 * @typedef {Object} Options
 * @property {string} code The SRS identifier code, e.g. `EPSG:4326`.
 * @property {import("./Units.js").Units} [units] Units. Required unless a
 * proj4 projection is defined for `code`.
 * @property {import("../extent.js").Extent} [extent] The validity extent for the SRS.
 * @property {string} [axisOrientation='enu'] The axis orientation as specified in Proj4.
 * @property {boolean} [global=false] Whether the projection is valid for the whole globe.
 * @property {number} [metersPerUnit] The meters per unit for the SRS.
 * If not provided, the `units` are used to get the meters per unit from the {@link METERS_PER_UNIT}
 * lookup table.
 * @property {import("../extent.js").Extent} [worldExtent] The world extent for the SRS.
 * @property {function(number, import("../coordinate.js").Coordinate):number} [getPointResolution]
 * Function to determine resolution at a point. The function is called with a
 * `number` view resolution and a {@link module:ol/coordinate~Coordinate} as arguments, and returns
 * the `number` resolution in projection units at the passed coordinate. If this is `undefined`,
 * the default {@link module:ol/proj.getPointResolution} function will be used.
 */

/**
 * @classdesc
 * In most cases, you should not need to create instances of this class.
 * Instead, where projection information is required, you can use a string
 * projection code or identifier (e.g. `EPSG:4326`) instead of a projection
 * instance.
 *
 * The library includes support for transforming coordinates between the following
 * projections:
 *
 *  * WGS 84 / Geographic - Using codes `EPSG:4326`, `CRS:84`, `urn:ogc:def:crs:EPSG:6.6:4326`,
 *    `urn:ogc:def:crs:OGC:1.3:CRS84`, `urn:ogc:def:crs:OGC:2:84`, `http://www.opengis.net/gml/srs/epsg.xml#4326`,
 *    or `urn:x-ogc:def:crs:EPSG:4326`
 *  * WGS 84 / Spherical Mercator - Using codes `EPSG:3857`, `EPSG:102100`, `EPSG:102113`, `EPSG:900913`,
 *    `urn:ogc:def:crs:EPSG:6.18:3:3857`, or `http://www.opengis.net/gml/srs/epsg.xml#3857`
 *  * WGS 84 / UTM zones - Using codes `EPSG:32601` through `EPSG:32660` for northern zones
 *    and `EPSG:32701` through `EPSG:32760` for southern zones. Note that the built-in UTM transforms
 *    are lower accuracy (with errors on the order of 0.1 m) than those that you might get in a
 *    library like [proj4js](https://github.com/proj4js/proj4js).
 *
 * For additional projection support, or to use higher accuracy transforms than the built-in ones, you can use
 * the [proj4js](https://github.com/proj4js/proj4js) library. With `proj4js`, after adding any new projection
 * definitions, call the {@link module:ol/proj/proj4.register} function.
 *
 * You can use the {@link module:ol/proj.get} function to retrieve a projection instance
 * for one of the registered projections.
 *
 * @api
 */
class Projection {
  /**
   * @param {Options} options Projection options.
   */
  constructor(options) {
    /**
     * @private
     * @type {string}
     */
    this.code_ = options.code;

    /**
     * Units of projected coordinates. When set to `TILE_PIXELS`, a
     * `this.extent_` and `this.worldExtent_` must be configured properly for each
     * tile.
     * @private
     * @type {import("./Units.js").Units}
     */
    this.units_ = /** @type {import("./Units.js").Units} */ (options.units);

    /**
     * Validity extent of the projection in projected coordinates. For projections
     * with `TILE_PIXELS` units, this is the extent of the tile in
     * tile pixel space.
     * @private
     * @type {import("../extent.js").Extent}
     */
    this.extent_ = options.extent !== undefined ? options.extent : null;

    /**
     * Extent of the world in EPSG:4326. For projections with
     * `TILE_PIXELS` units, this is the extent of the tile in
     * projected coordinate space.
     * @private
     * @type {import("../extent.js").Extent}
     */
    this.worldExtent_ =
      options.worldExtent !== undefined ? options.worldExtent : null;

    /**
     * @private
     * @type {string}
     */
    this.axisOrientation_ =
      options.axisOrientation !== undefined ? options.axisOrientation : 'enu';

    /**
     * @private
     * @type {boolean}
     */
    this.global_ = options.global !== undefined ? options.global : false;

    /**
     * @private
     * @type {boolean}
     */
    this.canWrapX_ = !!(this.global_ && this.extent_);

    /**
     * @private
     * @type {function(number, import("../coordinate.js").Coordinate):number|undefined}
     */
    this.getPointResolutionFunc_ = options.getPointResolution;

    /**
     * @private
     * @type {import("../tilegrid/TileGrid.js").default}
     */
    this.defaultTileGrid_ = null;

    /**
     * @private
     * @type {number|undefined}
     */
    this.metersPerUnit_ = options.metersPerUnit;
  }

  /**
   * @return {boolean} The projection is suitable for wrapping the x-axis
   */
  canWrapX() {
    return this.canWrapX_;
  }

  /**
   * Get the code for this projection, e.g. 'EPSG:4326'.
   * @return {string} Code.
   * @api
   */
  getCode() {
    return this.code_;
  }

  /**
   * Get the validity extent for this projection.
   * @return {import("../extent.js").Extent} Extent.
   * @api
   */
  getExtent() {
    return this.extent_;
  }

  /**
   * Get the units of this projection.
   * @return {import("./Units.js").Units} Units.
   * @api
   */
  getUnits() {
    return this.units_;
  }

  /**
   * Get the amount of meters per unit of this projection.  If the projection is
   * not configured with `metersPerUnit` or a units identifier, the return is
   * `undefined`.
   * @return {number|undefined} Meters.
   * @api
   */
  getMetersPerUnit() {
    return this.metersPerUnit_ || METERS_PER_UNIT[this.units_];
  }

  /**
   * Get the world extent for this projection.
   * @return {import("../extent.js").Extent} Extent.
   * @api
   */
  getWorldExtent() {
    return this.worldExtent_;
  }

  /**
   * Get the axis orientation of this projection.
   * Example values are:
   * enu - the default easting, northing, elevation.
   * neu - northing, easting, up - useful for "lat/long" geographic coordinates,
   *     or south orientated transverse mercator.
   * wnu - westing, northing, up - some planetary coordinate systems have
   *     "west positive" coordinate systems
   * @return {string} Axis orientation.
   * @api
   */
  getAxisOrientation() {
    return this.axisOrientation_;
  }

  /**
   * Is this projection a global projection which spans the whole world?
   * @return {boolean} Whether the projection is global.
   * @api
   */
  isGlobal() {
    return this.global_;
  }

  /**
   * Set if the projection is a global projection which spans the whole world
   * @param {boolean} global Whether the projection is global.
   * @api
   */
  setGlobal(global) {
    this.global_ = global;
    this.canWrapX_ = !!(global && this.extent_);
  }

  /**
   * @return {import("../tilegrid/TileGrid.js").default} The default tile grid.
   */
  getDefaultTileGrid() {
    return this.defaultTileGrid_;
  }

  /**
   * @param {import("../tilegrid/TileGrid.js").default} tileGrid The default tile grid.
   */
  setDefaultTileGrid(tileGrid) {
    this.defaultTileGrid_ = tileGrid;
  }

  /**
   * Set the validity extent for this projection.
   * @param {import("../extent.js").Extent} extent Extent.
   * @api
   */
  setExtent(extent) {
    this.extent_ = extent;
    this.canWrapX_ = !!(this.global_ && extent);
  }

  /**
   * Set the world extent for this projection.
   * @param {import("../extent.js").Extent} worldExtent World extent
   *     [minlon, minlat, maxlon, maxlat].
   * @api
   */
  setWorldExtent(worldExtent) {
    this.worldExtent_ = worldExtent;
  }

  /**
   * Set the getPointResolution function (see {@link module:ol/proj.getPointResolution}
   * for this projection.
   * @param {function(number, import("../coordinate.js").Coordinate):number} func Function
   * @api
   */
  setGetPointResolution(func) {
    this.getPointResolutionFunc_ = func;
  }

  /**
   * Get the custom point resolution function for this projection (if set).
   * @return {function(number, import("../coordinate.js").Coordinate):number|undefined} The custom point
   * resolution function (if set).
   */
  getPointResolutionFunc() {
    return this.getPointResolutionFunc_;
  }
}

export default Projection;