下载不了opencv-python，怎么解决

WARNING: You are using pip version 21.1.2; however, version 21.2.4 is available.
You should consider upgrading via the 'C:\Users\lyh\PycharmProjects\pythonProject5\venv\Scr
ipts\python.exe -m pip install --upgrade pip' command.

这是个warning,说你pip版本过低,如果下载失败是别的原因
如果不想看到这条提示,在cmd中输入

C:\Users\lyh\PycharmProjects\pythonProject5\venv\Scripts\python.exe -m pip install --upgrade pip

即可

pip install opencv-contrib-python -i https://pypi.tuna.tsinghua.edu.cn/simple

十有八九是源的问题，你截图最后的问题