Required skills: Python, maybe Cython

Difficulty: Easy

Our converter PNG export module supports 3 built-in compression levels

• none
• default libpng compression
• optimized compression

However, this functionality is currently unused as the converter is hardcoded to always use the default compression setting. We should implement a way to set the desired compression

The doc is great! Hoewever some areas are still missing.
C++11 intoduced raw string literals: https://en.cppreference.com/w/cpp/language/string_literal

It is useful in many different areas, like strings with quotes, multiline strings and for example windows paths without escaping backslashes:

const char win_path[] = R"(c:\some\unescaped\path)";

The same cppreference link als

多实例（主要是v2ray多实例）需求，主要是两个场景，且难以用其它方式替代。请拨冗考虑，未来是否可以增加此特性。

场景1、代理链式转发

在 #742 中关于代理链式转发的讨论，使用proxySettings代理出站流量的方向是对的，但在实操中，结合机场的订阅，需要将机场的信息编辑到复杂路由的json配置中，当切换线路时非常的麻烦。

我现在的做法，是机场的代理提供一个本地socks5服务，比如端口为10801，v2ray中配置一个socks协议的outbound，作为vmess的proxySetting。整个链路大致是这样的:

  浏览器  -> 
  # 代理
  socks://127.0.0.1:1080 -> vmess outbound (proxySetting on socks)-> socks outbound -> 
  #