Proposed module @turf/point-origin

[DenisCarriere]

Proposed module @turf/point-origin

Aimed for Turf v5.1 release

A module which defines a point of origin from a GeoJSON/BBox.

How to use

import pointOrigin from '@turf/point-origin'

const origin = pointOrigin(geojson, 'nw')
//=> North-West Feature<Point>

Refactoring for

Used to help define origin/pivot points

• @turf/transform-scale
• @turf/transform-rotate
• @turf/transform-translate

Already created in @turf/transform-scale

/**
 * Define Origin
 *
 * @private
 * @param {GeoJSON} geojson GeoJSON
 * @param {string|Geometry|Feature<Point>|Array<number>} origin sw/se/nw/ne/center/centroid
 * @returns {Feature<Point>} Point origin
 */
function defineOrigin(geojson, origin) {
    // Default params
    if (origin === undefined || origin === null) origin = 'centroid';

    // Input Geometry|Feature<Point>|Array<number>
    if (Array.isArray(origin) || typeof origin === 'object') return getCoord(origin);

    // Define BBox
    var bbox = (geojson.bbox) ? geojson.bbox : turfBBox(geojson);
    var west = bbox[0];
    var south = bbox[1];
    var east = bbox[2];
    var north = bbox[3];

    switch (origin) {
    case 'sw':
    case 'southwest':
    case 'westsouth':
    case 'bottomleft':
        return point([west, south]);
    case 'se':
    case 'southeast':
    case 'eastsouth':
    case 'bottomright':
        return point([east, south]);
    case 'nw':
    case 'northwest':
    case 'westnorth':
    case 'topleft':
        return point([west, north]);
    case 'ne':
    case 'northeast':
    case 'eastnorth':
    case 'topright':
        return point([east, north]);
    case 'center':
        return center(geojson);
    case undefined:
    case null:
    case 'centroid':
        return centroid(geojson);
    default:
        throw new Error('invalid origin');
    }
}