Port boost::python functionality over to pybind11

[mjcarroll]

This should potentially alleviate some of our porting headaches to other platforms.

Addresses #281

[mjcarroll]

And for giggles:

• Linux
• Linux-aarch64
• macOS
• Windows

[mjcarroll]

With correct library paths for tests:

• Linux
• Linux-aarch64
• macOS
• Windows

[mjcarroll]

macOS fails because of using OpenCV 4.

Windows fails because no boost/endian header.

[maxtong9]

Hey, I am trying to compile your branch on Windows 10 and I am getting this error:
fatal error C1083: Cannot open include file: 'numpy/ndarrayobject.h': No such file or directory
Am I missing some dependency? I have numpy installed via pip.
Great work on everything you've done! Windows 10 support seems to be lacking still for ROS 2 packages.

[mjcarroll]

I have to admit that I haven't sufficiently tested this on Windows. It may be that a numpy include path isn't getting picked up correctly on Windows? It would either be in the cmake logic here or in https://github.com/ros2/pybind11_vendor

[maxtong9]

Thank you for the quick response! I located where the header should be. I'm going to try and find a way to link it now!

[mjcarroll]

Rebuild macOS with OpenCV4 fix:

[jnoyola]

Just noticed you ran into the same issue as me on Windows (#289). Would you happen to know why this isn't an issue on the other OS's? Because the Boost include was removed altogether.

[jnoyola]

Is removing the version from OpenCV's find_package the only change needed to support OpenCV 4? Can we pull that into a separate PR to get it in faster?

[klintan]

Just noticed you ran into the same issue as me on Windows (#289). Would you happen to know why this isn't an issue on the other OS's? Because the Boost include was removed altogether.

I'm on Mac Mojave, and I got that exact issue as well for this branch
vision_opencv/cv_bridge/src/ndarray_converter.cpp:24:10: fatal error: 'numpy/ndarrayobject.h' file not found

I think except for that (if that is an issue here somewhere, it would be awesome to get this PR in to vision_opencv, support for opencv4 etc etc.

edit: fixing it for mac is fairly straightforward, just create a symlink for the numpy include headers to the user/local/include/ folder.

sudo ln -s /usr/local/Cellar/numpy/1.17.1/lib/python3.7/site-packages/numpy/core/include/numpy /usr/local/include/numpy

I'm not sure this is an issue in the CMakeLists file though ?
Tried to update the cmakelists like here ros2/rosidl_python#66 to no avail.

edit2:

After building it seems the library is missing, might just be me again, but I had to add

install(TARGETS ${PROJECT_NAME}
        RUNTIME DESTINATION bin
        ARCHIVE DESTINATION lib
        LIBRARY DESTINATION lib
)

To the cv_bridge cmakelists.txt file to actually export the library (it seems only the py-bindings get exported)

[ijnek]

@mjcarroll Considering this PR has been untouched for almost 3 years, I'm thinking of closing it out, but keeping the issue open.

Are you fine with this?

[mjcarroll]

Yep. Still would be nice to do, but it's been on the backburner for long enough that this is no longer relevant.

[ijnek]

Thanks @mjcaroll