@turf/mask

What is @turf/mask?

@turf/mask is a module in the Turf.js library that allows you to create a mask from a polygon. This mask can be used to clip or hide parts of other geometries that fall outside the polygon. It is particularly useful in geospatial analysis for focusing on specific areas of interest.

What are @turf/mask's main functionalities?

Create a Mask

This feature allows you to create a mask from a given polygon. The mask can then be used to clip other geometries, effectively hiding parts of them that fall outside the polygon.

const turf = require('@turf/turf');

const polygon = turf.polygon([[
  [-5, 52],
  [-4, 52],
  [-4, 53],
  [-5, 53],
  [-5, 52]
]]);

const mask = turf.mask(polygon);
console.log(JSON.stringify(mask));

Clip Geometry with Mask

This feature demonstrates how to use the mask to clip a line geometry. The resulting geometry will only include the parts of the line that fall within the mask polygon.

const turf = require('@turf/turf');

const polygon = turf.polygon([[
  [-5, 52],
  [-4, 52],
  [-4, 53],
  [-5, 53],
  [-5, 52]
]]);
const mask = turf.mask(polygon);

const line = turf.lineString([[-6, 51], [-3, 54]]);
const clipped = turf.mask(line, mask);
console.log(JSON.stringify(clipped));

Other packages similar to @turf/mask

turf-clip

The turf-clip package provides functionalities to clip geometries using polygons. It is similar to @turf/mask but focuses more on clipping rather than masking.

jsts

The jsts (JavaScript Topology Suite) library offers a wide range of spatial operations, including clipping and masking. It is more comprehensive than @turf/mask but also more complex to use.

geojson-merge

The geojson-merge package allows you to merge multiple GeoJSON objects into one. While it doesn't offer masking directly, it can be used in conjunction with other tools to achieve similar results.

README

@turf/mask

mask

Takes any type of polygon and an optional mask and returns a polygon exterior ring with holes.

Parameters

• polygon (FeatureCollection | Feature<(Polygon | MultiPolygon)>) GeoJSON Polygon used as interior rings or holes.
• mask [Feature<Polygon>] GeoJSON Polygon used as the exterior ring (if undefined, the world extent is used)

Examples

var polygon = {
  "type": "Feature",
  "properties": {},
  "geometry": {
    "type": "Polygon",
    "coordinates": [[[112, -21], [116, -36], [146, -39], [153, -24], [133, -10], [112, -21]]]
  }
}
var mask = {
  "type": "Feature",
  "properties": {},
  "geometry": {
    "type": "Polygon",
    "coordinates": [[[90, -55], [170, -55], [170, 10], [90, 10], [90, -55]]]
  }
}
var masked = turf.mask(polygon, mask);

//addToMap
var addToMap = [masked]

Returns Feature<Polygon> Masked Polygon (exterior ring with holes).

---

This module is part of the Turfjs project, an open source module collection dedicated to geographic algorithms. It is maintained in the Turfjs/turf repository, where you can create PRs and issues.

Installation

Install this module individually:

$ npm install @turf/mask

Or install the Turf module that includes it as a function:

$ npm install @turf/turf