Wheel support for linux aarch64

[odidev]

Summary
Installing opencv-python on aarch64 via pip using command "pip3 install opencv-python" throws error: No matching distribution found for opencv-python

Problem description
opencv-python doesn't have wheel for aarch64 on PyPI repository. So, while installing opencv-python via pip on aarch64, it throws an error " No matching distribution found for opencv-python".

Expected Output
Pip should be able to download opencv-python wheel from PyPI repository.

@opencv-pythonl-team, please let me know if I can help you building wheel/uploading to PyPI repository. I am curious to make opencv-pythonl wheel available for aarch64. It will be a great opportunity for me to work with you.

[skvark]

There are some issues which need to be solved before I can provide any support for this issue. However, you can start by looking at multibuild docs and start building similar Dockerfile and image as there are for i686 and x86_64 in the docker directory of this repository. After the Dockerfile is done and a working image based on it has been built building the wheels should be just a matter of adding new entries to .travis.yml given that the ARM workers in Travis have enough CPU power to run the build in under ~50 minutes.

[odidev]

Hi @skvark ,

I will start working on adding dockerfile and image for aarch64. Once it is done I will raise a PR the same.

Thanks

[skvark]

@odidev I managed to build the aarch64 image just by copying the x86_64 Dockerfile (didn't push it yet here) and changing the base image. It took 4 hours to build it with 8-core Ryzen 3700X (!), so not going to do it too often. The image is here: https://quay.io/repository/skvark/manylinux2014_aarch64

I'll try to make rest of the changes over weekend so we can see if OpenCV arm64 build is fast enough on Travis.

[odidev]

@skvark
Thanks for the looking int this issue.

Presently opencv-python builds are running on travis.ci.org. And recently arm64-graviton2 was inrtoduced for on travis-ci.com which is faster and have better performance.
Please have a look at this discussion

Using arm64-graviton2 will require opencv-python builds to migrate on travis-ci.com.
Please let me know your views and suggestions for this.

[skvark]

It should be fine to migrate to travis-ci.com but I'll have to test first that everything works there as expected. Unfortunately #376 took all my time this weekend so I'll look into this a bit later.

[odidev]

@skvark Thanks for the quick response. Please let me know if I can help you in this activity.

[skvark]

The migration to travis-ci.com has been now done: https://travis-ci.com/github/skvark/opencv-python

I'll have to rebuild the aarch64 image because it needs probably some additional tools to be built from scratch. I will look into that later.

[odidev]

@skvark Thanks for the migration to travis-ci.com. Please let me know if I can provide any help for rebuilding the aarch64 image/wheel .

[skvark]

The aarch64 Cmake provided via cmake is broken. There is CMake available also in the image which I built but the python cmake library doesn't seem to be using it. See aarch64 branch, cmake is defined as a build dependency in here: https://github.com/skvark/opencv-python/blob/feat/aarch64/pyproject.toml

This issue indicates that a broken wheel was removed from PyPI but the same issue is still present: scikit-build/cmake-python-distributions#96

[skvark]

Upstream issue: scikit-build/cmake-python-distributions#115

[AWSjswinney]

@skvark I'm working to improve arm64 support for python wheels, including this one. Once this cmake problem has been addressed, I'll be happy to assist you in getting your project to support arm64.

[skvark]

@AWSjswinney Thanks! arm64 support should be quite straightforward to add after the cmake issue has been solved.

[tom-gall]

I just ran across this issue. I seem to be hitting something a little different then what is reported with sci-kit. When I pip3 install opencv-python :

pip3 install opencv-python
Defaulting to user installation because normal site-packages is not writeable
Collecting opencv-python
Using cached opencv-python-4.4.0.44.tar.gz (88.9 MB)
Installing build dependencies ... done
Getting requirements to build wheel ... done
Preparing wheel metadata ... done
Requirement already satisfied: numpy>=1.14.5 in /home/debian/.local/lib/python3.7/site-packages (from opencv-python) (1.18.5)
Building wheels for collected packages: opencv-python
Building wheel for opencv-python (PEP 517) ... error
ERROR: Command errored out with exit status 1:
command: /usr/bin/python3 /home/debian/.local/lib/python3.7/site-packages/pip/_vendor/pep517/_in_process.py build_wheel /tmp/tmpoi10f9p3
cwd: /tmp/pip-install-wl_r1ytp/opencv-python
Complete output (9 lines):
File "/tmp/pip-build-env-r9enx4cm/overlay/lib/python3.7/site-packages/skbuild/setuptools_wrap.py", line 560, in setup
cmkr = cmaker.CMaker(cmake_executable)
File "/tmp/pip-build-env-r9enx4cm/overlay/lib/python3.7/site-packages/skbuild/cmaker.py", line 95, in init
self.cmake_version = get_cmake_version(self.cmake_executable)
File "/tmp/pip-build-env-r9enx4cm/overlay/lib/python3.7/site-packages/skbuild/cmaker.py", line 82, in get_cmake_version
"Problem with the CMake installation, aborting build. CMake executable is %s" % cmake_executable)
Traceback (most recent call last):

Problem with the CMake installation, aborting build. CMake executable is cmake

ERROR: Failed building wheel for opencv-python