ERROR: Could not build wheels for opencv-python-headless, which is required to install pyproject.tom

错误日志
pip 安装 ddddocr 模块报错
pip install ddddocr
ERROR: Failed building wheel for opencv-python-headless
Failed to build opencv-python-headless
ERROR: Could not build wheels for opencv-python-headless, which is required to install pyproject.toml-based projects

报错原因
opencv-python-headless 模块安装不上
解决办法
我们直接使用 whl 文件离线安装方法
去 pypi( opencv-python-headless · PyPI ) 官网下载对应版本的 whl
我的环境是 py3.6.8 win 64 位,所以我下载的是红框中的

安装过程:
(work_py) E:\>pip install E:\downloads\opencv_python_headless-3.4.18.65-cp36-abi3-win_amd64.whl
Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple
Processing e:\downloads\opencv_python_headless-3.4.18.65-cp36-abi3-win_amd64.whl
Requirement already satisfied: numpy>=1.13.3 in e:\py_envs\work_py\lib\site-packages (from opencv-python-headless==3.4.18.65) (1.19.5)
Installing collected packages: opencv-python-headless
Successfully installed opencv-python-headless-3.4.18.65
(work_py) E:\>pip install ddddocr
Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple
Collecting ddddocr
Using cached https://pypi.tuna.tsinghua.edu.cn/packages/2b/03/cd7a1998cc435322956c8368bd621176ea50e4e6cbb778b3ba24d19fef8f/ddddocr-1.4.7-py3-none-any.whl (75.9 MB)
Requirement already satisfied: opencv-python-headless in e:\py_envs\work_py\lib\site-packages (from ddddocr) (3.4.18.65)
Requirement already satisfied: Pillow in e:\py_envs\work_py\lib\site-packages (from ddddocr) (8.4.0)
Requirement already satisfied: numpy in e:\py_envs\work_py\lib\site-packages (from ddddocr) (1.19.5)
Collecting onnxruntime
Using cached https://pypi.tuna.tsinghua.edu.cn/packages/57/62/544bd705f3a7d0a24a66747680d95dc78050cdce613ced19c676c4ff4019/onnxruntime-1.10.0-cp36-cp36m-win_amd64.whl (5.2 MB)