完整错误信息：

QObject::moveToThread: Current thread (0x5621b4823b40) is not the object's thread (0x5621b6f72df0).
Cannot move to target thread (0x5621b4823b40)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/zxq/anaconda3/envs/open-mmlab/lib/python3.7/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl.
 

网上找了一上午，适合我的解决办法是降低opencv-python版本，记录下备忘：

pip install opencv-python==4.1.0.25 -i https://pypi.douban.com/simple
pip install opencv-contrib-python -i https://pypi.douban.com/simple