bpgl_algo importlib

[NoahRJohnson]

Add importlib imports for vgl, vil, vpgl as these libraries are used in the arguments of functions within bpgl_algo. This resolves Issue #119, removing the need to first import vxl.vgl before importing vxl.contrib.bpgl.algo.

[NoahRJohnson]

This is related to the broader Issue #107

[drewgilliam]

Would it be cleaner to add to the import list in the __init__.py file?

from ._bpgl_algo import *
from vxl import vgl, vil, vpgl

Also, I'm guessing we don't see this error in CI because there are no tests for bpgl.algo?

[NoahRJohnson]

Would it be cleaner to add to the import list in the __init__.py file?

from ._bpgl_algo import *
from vxl import vgl, vil, vpgl

Also, I'm guessing we don't see this error in CI because there are no tests for bpgl.algo?

Yes, but even if we added bpgl_algo tests, we wouldn't see this error unless we explicitly imported vxl.contrib.bpgl.algo before vxl.vgl. test_pyacal doesn't import acal first, so maybe that's a design pattern we should enforce in each test file.

Adding to the import list in the init.py works, but only if we import vgl first:

from vxl import vgl, vil, vpgl
from ._bpgl_algo import *

otherwise the _bpgl_algo import still fails with an ImportError as below
user@7d694eb4189b:/$ python -c "import vxl.contrib.bpgl.algo" Traceback (most recent call last): File "<string>", line 1, in <module> File "/install/lib/python3/site-packages/vxl/contrib/bpgl/algo/__init__.py", line 1, in <module> from ._bpgl_algo import * ImportError: arg(): could not convert default argument 'target_window: vgl_box_2d<int>' in method '<class 'vxl.contrib.bpgl.algo._bpgl_algo.rectify_image_pair_affine'>.process' into a Python object (type not registered yet?)

I don't remember if there's any reason not to do it this way.

[drewgilliam]

superceded by PR #122