Could not find a version that satisfies the requirement cv2

python缺少cv2，以为安装方法如下：

>pip install cv2

但是报错，报错信息如下：

（我用的‘’pycharm，直接在setting->project interpreter中安装也显示下面的错误）
Collecting cv2
  Could not find a version that satisfies the requirement cv2 (from versions: )
No matching distribution found for cv2

 

 

正确的安装方法是：

pip install opencv-python