js-squares-hull-2d

Calculate the outer hull of a 2d matrix of same size, touching squares

Install

npm i js-squares-hull-2d
# yest add js-squares-hull-2d

Usage

import getHull, { Matrix } from 'js-squares-hull-2d';

/* 0  1 2 x
   1 █▌
   2 █▌█▌
   y */
const matrix: Matrix<string> = [['█▌'], ['█▌', '█▌']];

/*
 _
|  `.
|___|
*/
const hull = getHull();

console.log(hull);
/* [
  { x: 0, y: 0 },
  { x: 1, y: 0 },
  { x: 2, y: 1 },
  { x: 2, y: 2 },
  { x: 0, y: 2 }
] */

Values

This library does not care about the values in the matrix as long as they're truthy. The examples on this page and the spec uses "█▌" for symbolic representation.

In real projects this is meant to work with game elements in the matrix.

import type { Matrix } from 'js-squares-hull-2d';
import { Element } from './myGame';

const matrix: Matrix<Element> = [[new Element({ color: 'blue', mass: 5 })]];

Optimizations

1. diagonals are normalized

"Steps" are being treated as 45deg diagonals

         _
█▌   => |  `.
█▌█▌ => |___|

Meaning this hull will never be produced

         _
█▌   x> | |_
█▌█▌ x> |___|

2. Long borders sub-points are removed

import getHull from 'js-squares-hull-2d';

console.log(getHull([['█▌', '█▌', '█▌']]));
/* [
  { x: 0, y: 0 },
  { x: 3, y: 0 },
  { x: 3, y: 1 },
  { x: 0, y: 1 },
] */

Note the absence of points { x: 1, y: 0 }, { x: 2, y: 0 } etc..

3. Falsy values are ignored

import getHull from 'js-squares-hull-2d';

/* 0  1 2 x
   1   █▌
   2 █▌█▌
   y */
const matrix = [
  [null, '█▌'],
  ['█▌', '█▌'],
];

/*
   _
 .` |
|___|
*/
const hull = getHull(matrix);
console.log();
/* [
  { x: 1, y: 0 },
  { x: 2, y: 0 },
  { x: 2, y: 2 },
  { x: 0, y: 2 },
  { x: 0, y: 1 }
] */

License

The MIT License

Copyright (C) 2020 Hannes Diercks

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.