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

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 -> 
  #

Current compilervars is not exposed via conans.tools which means that only conanfiles that make use of the CMake and vcproj build helpers can reasonably use the Intel compiler. Please export compilervars and the _dict and _command variants in the conans.tools module.

Blocker for conan-io/conan-center-index#2499.

• I've read the [CONTRIBUTING guide](https://git

We are in the process of dropping Math.h and one of the more commonly used operation there is fequals, which checks if the difference between two values is less than the type's epsilon. The task is to write this as a free function, probably in a new file in the util directory and drop Math::fequals.

Bug Report

This happened on Windows with the Pro IDE. This is all I can see in the logs:

root ERROR Uncaught Exception:  Error: 2 UNKNOWN: error getting port list from serial-discovery: read |0: The handle is invalid.
root ERROR Error: 2 UNKNOWN: error getting port list from serial-discovery: read |0: The handle is invalid.
    at Object.callErrorFromStatus (c:\Users\kittaakos\Desktop\

Possible place where the amount of "kills" a unit has done would be up here, after everything.