Source: tiny/core/math/shapes/Polygon.js

import Point from '../Point';
import { SHAPES } from '../../const';

/**
 * @class
 * @memberof Tiny
 */
export default class Polygon {
  /**
   * @param {Tiny.Point[]|number[]} points - This can be an array of Points that form the polygon, a flat array of numbers that will be interpreted as [x,y, x,y, ...], or the arguments passed can be all the points of the polygon e.g. `new Tiny.Polygon(new Tiny.Point(), new Tiny.Point(), ...)`, or the arguments passed can be flat x,y values e.g. `new Polygon(x,y, x,y, x,y, ...)` where `x` and `y` are Numbers.
   */
  constructor(...points) {
    if (Array.isArray(points[0])) {
      points = points[0];
    }

    // if this is an array of points, convert it to a flat array of numbers
    if (points[0] instanceof Point) {
      const p = [];

      for (let i = 0, il = points.length; i < il; i++) {
        p.push(points[i].x, points[i].y);
      }

      points = p;
    }

    this.closed = true;

    /**
     * An array of the points of this polygon
     *
     * @member {number[]}
     */
    this.points = points;

    /**
     * The type of the object, mainly used to avoid `instanceof` checks
     *
     * @member {number}
     * @readOnly
     * @default Tiny.SHAPES.POLY
     * @see Tiny.SHAPES
     */
    this.type = SHAPES.POLY;
  }

  /**
   * Creates a clone of this polygon
   *
   * @return {Tiny.Polygon} a copy of the polygon
   */
  clone() {
    return new Polygon(this.points.slice());
  }

  /**
   * Closes the polygon, adding points if necessary.
   *
   */
  close() {
    const points = this.points;

    // close the poly if the value is true!
    if (points[0] !== points[points.length - 2] || points[1] !== points[points.length - 1]) {
      points.push(points[0], points[1]);
    }
  }

  /**
   * Checks whether the x and y coordinates passed to this function are contained within this polygon
   *
   * @param {number} x - The X coordinate of the point to test
   * @param {number} y - The Y coordinate of the point to test
   * @return {boolean} Whether the x/y coordinates are within this polygon
   */
  contains(x, y) {
    let inside = false;

    // use some raycasting to test hits
    // https://github.com/substack/point-in-polygon/blob/master/index.js
    const length = this.points.length / 2;

    for (let i = 0, j = length - 1; i < length; j = i++) {
      const xi = this.points[i * 2];
      const yi = this.points[(i * 2) + 1];
      const xj = this.points[j * 2];
      const yj = this.points[(j * 2) + 1];
      const intersect = ((yi > y) !== (yj > y)) && (x < ((xj - xi) * ((y - yi) / (yj - yi))) + xi);

      if (intersect) {
        inside = !inside;
      }
    }

    return inside;
  }
}
Documentation generated by JSDoc 3.4.3 on Fri Jul 09 2021 19:32:25 GMT+0800 (CST)