Use the Outer glow option to add a very slight grey border, adjusting the Spread to the Max will turn the default glow into a solid strip of colour which helps add this double stroke effect.
继续用外发光来添加一个浅灰色的边，调整扩展值到最大这样我们可以得到一个双边线效果。
3
But, you know, it gives you an example where you can turn are really hard line integral into an easier double integral.