Support loading meshes from file objects

[mancellin]

It would be nice to be able to load a mesh not only from a file name but also from an already opened file object.

Usage example:

import gzip
with gzip.open("meshes/viking_ship.stl.gz") as f:
    mesh = cpt.load_mesh(f, file_format="stl")

Python standard library include reader for various compressed file format (zip, gzip, etc.), it would be nice to be able to be able to compose them with Capytaine.

[mancellin]

Work-around using a temporary file:

import gzip, tempfile, shutil
with tempfile.NamedTemporaryFile('wb') as tmp_f:
    with gzip.open("meshes/viking_ship.stl.gz") as f:
        shutil.copyfileobj(f, tmp_f)
        mesh = cpt.load_mesh(tmp_f.name, file_format="stl", name=f.name)

[mancellin]

We could imagine that each load_XXX function supports either a filepath, a file object or raw data (text string or byte string).

Currently, some of them

• work on the raw data by extracting it from the file in their first lines
• call an external library (notably vtk) that may not support passing raw data and accept only a filename

We could define decorator that

• when given a file or file object, extract the data and pass it to the function
• when given raw data or a file object, write them in a temporary file and pass the filepath to the function.

The latter might be replaced by just raising an error as I'm not sure it would be so useful actually to implement that...
By applying each decorator to each kind of function, all function could support all the cases.