projection.Common

projection.Common is the mixin base class for projections, providing default identity project/unproject implementations as well as batch projection and sphere-checking utilities. It is an object mixin with no standalone constructor: it is mixed into concrete projections such as projection.EPSG3857, projection.BAIDU, and projection.EPSG4326. Its code defaults to an empty string and project/unproject default to returning the input coordinate unchanged.

import { projection } from "maptalks";

// Concrete projections inherit from Common
const proj = projection.EPSG3857;
console.log(proj.code); // "EPSG:3857"

Properties / Static Methods

• code: string — The projection code, default '', overridden by subclasses.
• aliases: string[] — Alias list of the projection, e.g. ['Traverse_Mercator'].
• circum — Cached sphere circumference, shaped { x, y }.
• sphere — The sphere measurer, indicating whether the projection is spherical (e.g. WGS84Sphere).
• extent — Cached sphere extent (Extent).

Methods

• is(code): boolean — Whether the projection code or one of its aliases equals the passed code.
• project(p): Coordinate — Project a geographical coordinate to a projected coordinate, identity by default.
• unproject(p): Coordinate — Unproject a projected coordinate back to a geographical coordinate, identity by default.
• projectCoords(coords, antiMeridian?): Coordinate[] — Project a batch of coordinates, supporting 1D/multi-dimensional arrays and handling antimeridian crossing.
• unprojectCoords(coords): Coordinate[] — Unproject a batch of projected coordinates.
• isSphere(): boolean — Whether the projection is spherical.
• isOutSphere(pcoord): boolean — Whether the projected coordinate is out of the sphere.
• wrapCoord(pcoord): Coordinate — Wrap the projected coordinate into the sphere extent.
• getCircum(): { x, y } — Get or compute the sphere circumference (width, height).
• getSphereExtent(): Extent — Get or compute the sphere extent.