Inserting center coordinates to ellipsoid

[alexdesiqueira]

Description

Inserting center coordinates to ellipsoid.

Checklist

• Docstrings for all functions
• Gallery example in ./doc/examples (new features only)
• Benchmark in ./benchmarks, if your changes aren't covered by an
  existing benchmark
• Unit tests
• Clean style in the spirit of PEP8

For reviewers

• Check that the PR title is short, concise, and will make sense 1 year
  later.
• Check that new functions are imported in corresponding __init__.py.
• Check that new features, API changes, and deprecations are mentioned in
  doc/release/release_dev.rst.
• Consider backporting the PR with @meeseeksdev backport to v0.14.x

[pep8speaks]

Hello @alexdesiqueira! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file skimage/draw/draw3d.py:

Line 57:49: W504 line break after binary operator
Line 58:49: W504 line break after binary operator
Line 61:49: W504 line break after binary operator
Line 62:49: W504 line break after binary operator

[rfezzani]

center seems not to be the correct parameter name. Isn't shift better since the ellipsoid is shifted relatively to the returned volume center?
Shouldn't the shape of the returned volume be adapted such that it contains the whole generated ellipsoid?

[rfezzani]

center argument should be documented.

[rfezzani]

Add a test for center length, otherwise the unpacking will raise an error.

[alexdesiqueira]

@rfezzani:

center seems not to be the correct parameter name. Isn't shift better since the ellipsoid is shifted relatively to the returned volume center?

I think we should define something consistent with the other algorithms (if that's the not case, i.e., if this is a specific case for this algorithm and needs a different name, please let me know why or point me a reference).

Shouldn't the shape of the returned volume be adapted such that it contains the whole generated ellipsoid?

Maybe. If that's the case we could try to solve this two things "at once"; I'll ask for @sciunto's input in it.

[rfezzani]

Hi @alexdesiqueira, the way you defined center does not correspond to a coordinate in the returned volume.
In fact, in your implementation, when center=(0, 0, 0), the center of the ellipsoid is located at floor(a+1, b+1, c+1) , ie at the center of the returned volume. That's why I proposed to rename this parameter.