d3plus-shape/es/src/geom/path2polygon.js

Fancy SVG shapes for visualizations

import pointDistance from "./pointDistance";
import shapeEdgePoint from "./shapeEdgePoint";
var pi = Math.PI;
/**
    @function path2polygon
    @desc Transforms a path string into an Array of points.
    @param {String} path An SVG string path, commonly the "d" property of a <path> element.
    @param {Number} [segmentLength = 20] The lenght of line segments when converting curves line segments. Higher values lower computation time, but will result in curves that are more rigid.
    @returns {Array}
*/

export default (function (path) {
  var segmentLength = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 20;
  var poly = [],
      regex = /([MLA])([^MLAZ]+)/ig;
  var match = regex.exec(path);

  while (match !== null) {
    if (["M", "L"].includes(match[1])) poly.push(match[2].split(",").map(Number));else if (match[1] === "A") {
      var points = match[2].split(",").map(Number);
      var last = points.slice(points.length - 2, points.length),
          prev = poly[poly.length - 1],
          radius = points[0],
          width = pointDistance(prev, last);
      var angle = Math.acos((radius * radius + radius * radius - width * width) / (2 * radius * radius));
      if (points[2]) angle = pi * 2 - angle;
      var step = angle / (angle / (pi * 2) * (radius * pi * 2) / segmentLength);
      var start = Math.atan2(-prev[1], -prev[0]) - pi;
      var i = step;

      while (i < angle) {
        poly.push(shapeEdgePoint(points[4] ? start + i : start - i, radius));
        i += step;
      }

      poly.push(last);
    }
    match = regex.exec(path);
  }

  return poly;
});