polygon-eq

compare if two polygons are equal. multipolygons and holes supported.

The comparison ignores whether or not there is a duplicate first and last node.

Rings with reversed orders (clockwise or counter-clockwise) are considered equal if their points are equal. Holes and sub-polygons can appear in any order.

The data for polygons is pretty much geojson coordinates field for polygons types but more lenient.

example

single polygons:

var eq = require('polygon-eq')
var A = [[6.25,6],[10,12],[10,4],[7.5,4],[10,0],[0,0],[5,8]]
var B = [[10,0],[7.5,4],[10,4],[10,12],[6.25,6],[5,8],[0,0],[10,0]]
var C = [[6.25,6],[10,12],[7.5,4],[10,4],[10,0],[0,0],[5,8]]
console.log(eq(A,B)) // true
console.log(eq(A,C)) // false

single polygons with holes:

var eq = require('polygon-eq')
var A = [
  [[5,8],[6.25,6],[10,12],[15,-2],[7,-2],[8,0],[0,0],[5,8]],
  [[8.889,1.778],[10,4],[7.5,4],[8.889,1.778]]
]
var B = [
  [[6.25,6],[5,8],[0,0],[8,0],[7,-2],[15,-2],[10,12]],
  [[7.5,4],[8.889,1.778],[10,4],[7.5,4]]
]
var C = [
  [[6.25,6],[5,8],[0,0],[8,0],[7,-2],[15,-2],[10,12]],
  [[7.5,4],[8.889,1.778],[10,4.1]],
]
console.log(eq(A,B)) // true
console.log(eq(A,C)) // false

multipolygons, some polygons with holes, some without:

var eq = require('polygon-eq')
var A = [
  [
    [[6.25,6],[10,12],[15,-2],[7,-2],[8,0],[0,0],[5,8]],
    [[8.889,1.778],[10,4],[7.5,4],[8.889,1.778]],
  ],
  [[[-4,+4],[-4,+7],[-2,+5],[-4,+4]]],
]
var B = [
  [[[-4,+7],[-4,+4],[-2,+5],[-4,+7]]],
  [
    [[6.25,6],[5,8],[0,0],[8,0],[7,-2],[15,-2],[10,12],[6.25,6]],
    [[7.5,4],[8.889,1.778],[10,4]],
  ],
]
console.log(eq(A,B)) // true

api

var eq = require('polygon-eq')

eq(A, B, epsilon=1e-8)

Return a boolean, whether or not polygons A and B are equal.

Polygons work like the geojson coordinates field for polygon and multipolygon types but can also be depth 2 and do not require that the first point and last point are equal in a ring.

• depth=2 - single polygon: [[x0,y0],[x1,y1],...]
• depth=3 - single polygon with holes: [[[x0,y0],[x1,y1],...],hole0,hole1...]
• depth=4 - multiple polygons, each with holes: [polygon0,polygon1,...]

Each hole is formatted like a single polygon: [[x0,y0],[x1,y1],...].

install

npm install polygon-eq

license

bsd