opencv.js 中如何 获取 cv.approxPolyDP 多边形的顶点

你好， @daidai21， @jiangzhonglian ，我这边使用opencv.js 4.6.0版本的，使用cv.approxPolyDP(cnt, tmpMat, 0.01 * cntLen, true);把值赋值给tmpMat，我想通过tmpMat获取多边形的各个顶点，我的例子中是不规则多边形是一个不规则的四边形，请问有方法可以调用获取不规则四边形的四个顶点吗？

The issue names no file or test; start at the cv.approxPolyDP entry point in the OpenCV.js 4.6.0 documentation and inspect how its output tmpMat is represented. Done means documenting how to obtain the polygon vertices, including the irregular quadrilateral case, with a reproducible example or referenced API behavior.

Written by the indexing model from the issue text.