how do I type-hint numpy arrays (OpenCV images) in Python?

Question

This question is not about what data the OpenCV image contains but about what type information to put into a python function.

What I do now is:

import numpy as np
import cv2

Mat = np.ndarray

def my_fun(image: Mat):
    cv2.imshow('display', image)
    cv2.waitKey()

Is there any better way to add typing information for OpenCV images in python?

Answer 1

You can specify it as numpy.typing.NDArray with an entry type. For example,

import numpy as np

Mat = np.typing.NDArray[np.uint8]

def my_fun(img: Mat):
    pass