function softenDots(value, { maxStroke = 10 }) {
  return glyph => glyph.map(contour => {
    if (!isDot(contour, maxStroke)) return contour;
    return contour.map((pt, i) => {
      if (pt.on) return pt;
      const target = dotOffPointTarget(contour, i);
      const p = tuple(pt);
      const result = add(mul(value, p), mul(1-value, target));
      return { x: result[0], y: result[1], on: false };
    });
  });
}
Soften the dot strokes
@param { number } value
@param { { maxStroke: number } } config
@returns { PostFilter }