@thi.ng/geom-clip-poly/index.js

2D polygon clipping / offsetting (Sutherland-Hodgeman, Grainer-Hormann)

import { intersectLineLine } from "@thi.ng/geom-isec/line-line";
import { centroid } from "@thi.ng/geom-poly-utils/centroid";
import { EPS } from "@thi.ng/math/api";
import { corner2 } from "@thi.ng/vectors/clockwise";
const sutherlandHodgeman = (pts, bounds, bc, eps = EPS) => {
  bc = bc || centroid(bounds);
  for (let ne = bounds.length, j = ne - 1, i = 0; i < ne; j = i, i++) {
    const clipped = [];
    const ca = bounds[j];
    const cb = bounds[i];
    const sign = corner2(ca, cb, bc, eps);
    for (let np = pts.length, k = np - 1, l = 0; l < np; k = l, l++) {
      const p = pts[k];
      const q = pts[l];
      const cqsign = corner2(ca, cb, q, eps);
      if (corner2(ca, cb, p, eps) === sign) {
        clipped.push(
          cqsign !== sign ? intersectLineLine(ca, cb, p, q).isec[0] : q
        );
      } else if (cqsign === sign) {
        clipped.push(intersectLineLine(ca, cb, p, q).isec[0], q);
      }
    }
    if (clipped.length < 2) {
      return [];
    }
    pts = clipped;
  }
  return pts;
};
export {
  sutherlandHodgeman
};