Numpy 2 compatible build

[dkbarn]

I haven't managed to find any previous discussion about this, although I'm surprised by that so I very well may have missed it.

Numpy 2 is coming: numpy/numpy#24300

Are there any plans to begin providing nightly builds of OpenCV Python bindings which are ABI compatible with Numpy 2? Instructions are provided here on how to do that: https://numpy.org/devdocs/dev/depending_on_numpy.html#numpy-2-0-specific-advice

Currently when I pip install opencv-python-rolling it is not ABI compatible:

# create a virtualenv
$ python -m venv testvenv

# install numpy 2.x
$ testvenv/bin/pip install --pre -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple numpy

# install opencv-python-rolling
$ testvenv/bin/pip install opencv-python-rolling

$ testvenv/bin/python
>>> import cv2
RuntimeError: module compiled against ABI version 0x1000009 but this version of numpy is 0x2000000
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/share/dev/src/testvenv/lib/python3.10/site-packages/cv2/__init__.py", line 181, in <module>
    bootstrap()
  File "/share/dev/src/testvenv/lib/python3.10/site-packages/cv2/__init__.py", line 153, in bootstrap
    native_module = importlib.import_module("cv2")
  File "/usr/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
ImportError: numpy.core.multiarray failed to import

[dkbarn]

Note that numpy 2.0.0rc1 is now publicly available: numpy/numpy#24300 (comment)

[nabobalis]

Is there anything we can do to help with checking support for numpy 2.0?

[asmorkalov]

2 items in scope:

• Numpy 2.0 support in main repo: bindings generator, cv.Mat, type hints. Submitted Implement Numpy 2.0 support in Python bindings opencv#25455 to track it.
• OpenCV-Python package build. M.b. 2 branches of binary packages. Let's track it here.