bbox-fns

bbox-fns: work in progress

Super Light-weight JavaScript Bounding Box Utility Functions

usage

the bounding box

Bounding boxes, or rectangular extents, are represented as an array of 4 numbers:

[xmin, ymin, xmax, ymax]

bboxArray

Calculate the bounding box of an array of points (aka "a polygon ring")

import bboxArray from "bbox-fns/bbox-array.js";

bboxArray([
  [ -180, 86.06126914660831 ],
  [ -180, 85.66739606126914 ],
  [ -179, 84.87964989059081 ],
  [ -179, 84.48577680525165 ]
]);
[-180, 84.48577680525165, -179, 86.06126914660831]

booleanIntersects

Checks if two bounding boxes have any intersection at all.

import booleanIntersects from "bbox-fns/boolean-intersects.js";

const western_hemisphere = [-180, -90, 0, 90];
const eastern_hemisphere = [0, -90, 180, 90];

booleanIntersects(western_hemisphere, eastern_hemisphere);
true

intersect

import intersect from "bbox-fns/intersect.js";
const western_hemisphere = [-180, -90, 0, 90];
const eastern_hemisphere = [0, -90, 180, 90];

intersect(western_hemisphere, eastern_hemisphere);
[0, -90, 0, 90] // prime meridian

polygon

Create GeoJSON-Like Polygon from a Bounding Box

import polygon from "bbox-fns/polygon.js";

polygon([-180, -90, 180, 90]);

// polygon is in counter-clockwise order
[
  [
    [-180, 90],  // top-left
    [-180, -90], // bottom-left
    [180, -90],  // bottom-right
    [180, 90],   // top-right 
    [-180, 90]   // top-left
  ]
]

densePolygon

A more advanced version of polygon. Create a polygon while adding points to each side of the rectangle.

import polygon from "bbox-fns/dense-polygon.js";

// add 100 points along each side
densePolygon(bbox, { density: 100 });

// add 100 points along the top and bottom edge (x-axis)
// and 400 points along the left and right edge (y-axis)
densePolygon(bbox, { density: [100, 400] });

reproject

Reproject a bounding box using the given reprojection function

import reproject from "bbox-fns/reproject.js";
import proj4 from "proj4-fully-loaded";

// convert a bounding box from 4326 to a UTM projection
const { forward } = proj4("EPSG:4326", "EPSG:32610");
reproject(bbox, forward);

// you can also pass in an async reprojection function
reproject(bbox, forwardAsync, { async: true })

// you can also control the point density of the intermediate polygon
reproject(bbox, forward, { density: 99 })

projection support

If you are looking for a library with greater projection support and a class-based approach, try geo-extent!

nomenclature

This library borrows the names of some similar Turf.js functions, but it does not borrow the internal code.