Reference · Framing, geometry and quiz tools
projectPointfunction
Where a longitude and latitude (in degrees) fall on the map's canvas, as [x, y]; null for a map whose canvas
cannot be reversed from here. On the world a point just east of the seam is at the far left of the canvas and one just
west of it at the far right, and the canvas repeats either side, so a page that pans past the edge adds or takes away
width (wrapAcross).
Import it
import { projectPoint } from "@johnmorrisdotca/chizu";Definition
function projectPoint(map: Pick<ChizuMap, "projection">, lon: number, lat: number): [number, number] | nullParameters
| Name | Type | Description |
|---|---|---|
map | Pick<ChizuMap, "projection"> | The native map or map fields required by this signature; coordinates and region codes belong to its canvas. |
lon | number | Longitude in degrees, in [longitude, latitude] order. |
lat | number | Latitude in degrees, in [longitude, latitude] order. |
Returns
[number, number] | null
The native [x, y] point, or null when the map’s projection is not reversible here.
Examples
import WORLD from "@johnmorrisdotca/chizu/world";
import { projectPoint } from "@johnmorrisdotca/chizu";
const tokyo = projectPoint(WORLD, 139.69, 35.69)!;
console.log(tokyo.map((value) => value.toFixed(1)).join(", "));
// 457.5, 212.5457.5, 212.5What it prints (run when this page was built)