add [inv|fwd]_intermediate() - to calculate intermediate points (like improved Geod.npts())

[idanmiara]

pyproj/geod.py - add a parameter return_points to Geod.npts() to determinate the return type; improve return type hint
pyproj/geod.py - add a parameters initial_idx, terminus_idx to Geod.npts()
pyproj/[geod.py, _geod.pyi, _geod.pyx] - add inv_intermediate_by_npts functions that uses given buffers out_lons, out_lats (and out_azis) buffers instead of creating new buffers
pyproj/_geod.pxd - add interface for geod_lineinit
pyproj/[geod.py, _geod.pyi, _geod.pyx] - add inv_intermediate_by_del, fwd_intermediate_by_npts, fwd_intermediate_by_del functions, similar to inv_npts but using forward calculation
test/test_geod.py - add tests for new functions

Related PR

#825

[idanmiara]

Maybe I'll change this flag into an tuple of Enum so other return types could be supported in the future, like (points, lons, lats, ranges, azimuths)

[snowman2]

@idanmiara, I am planning on doing a release soon since PROJ 8.0.1 was just released. Do you want to try to include this in this release or do you need more time?

[idanmiara]

@idanmiara, I am planning on doing a release soon since PROJ 8.0.1 was just released. Do you want to try to include this in this release or do you need more time?

Hi, thanks for your letting me know!
I'm trying to complete it now.

[idanmiara]

I had a few other related ideas, I've implemented them in geod.py but I see that I can probably implement them much more efficiently in Cython by modifying _geod.Geod._npts:

1. add a flag add_points: int add an option to add initial and/or terminus points to the output vector (0= default- add neither, 1=add first; 2=add last; 3= add both)
2. add an optional az: float parameter to allow to calculate the line by using az instead of lon2, lat2 using geod_lineinit (like before REF: Update pyproj.Geod.npts to use geod_inverseline #825)
3. add optional del_s: float and n_ceil: bool that can be an alternative way to calculate the number of points number (https://github.com/pyproj4/pyproj/pull/825/files#diff-884caf2af6e10fc8e0b305d38b427edc7b43d9ed3ec739aed1be2de94049ab7dR192):

    npts = dist / del_s
    if n_ceil:
        npts = math.ceil(npts)
    npts = int(npts)

    dist = npts * del_s

4. optionally add a pazi2 vector to the output (https://github.com/pyproj4/pyproj/pull/825/files#diff-884caf2af6e10fc8e0b305d38b427edc7b43d9ed3ec739aed1be2de94049ab7dR196) by adding another return type option

I've never used Cython before. from what I see it's not too complicated. Do you have some pointers on how to start besides the Cython official tutorials? How do you debug it?

I'm thinking if I can make it to the next release, when are you planning on making it?

[snowman2]

Do you have some pointers on how to start besides the Cython official tutorials? How do you debug it?

That sounds like a good place to start. Also, looking through the existing code could be helpful.

For debugging, I usually rebuild the cython after each change with:

pip install -e . or python setup.py build_ext --inplace

And then test it like normal python code.

[snowman2]

I'm thinking if I can make it to the next release, when are you planning on making it?

No rush. If you are regularly working on it, it can wait until you are done.

[snowman2]

One thought I had was to potentially break out the different types of inputs/responses into different methods. This will add clarify for expected input/output to the user and simplify the logic for each method.

[snowman2]

I see a commit where you say: ".. versionadded:: 3.1.0" with ".. versionadded:: 3.1" for consistency that modifies the crs/transformer files. Would you mind moving this to a separate PR for clarity? And, if you are feeling extra motivated, you could do a search for versionadded and make all of them consistent in that PR, but definitely not necessary.

[snowman2]

@idanmiara thanks for your patience with this PR! I think it is very close to being ready for merge.

[idanmiara]

I see a commit where you say: ".. versionadded:: 3.1.0" with ".. versionadded:: 3.1" for consistency that modifies the crs/transformer files. Would you mind moving this to a separate PR for clarity? And, if you are feeling extra motivated, you could do a search for versionadded and make all of them consistent in that PR, but definitely not necessary.

Sure.

[idanmiara]

@idanmiara thanks for your patience with this PR! I think it is very close to being ready for merge.

Thank you, I highly appreciate your thorough review!

[snowman2]

@idanmiara this looks good. Ready to merge?

[idanmiara]

@idanmiara this looks good. Ready to merge?

Absolutely!

[snowman2]

Thanks @idanmiara 👍