Adding spacing to extra_properties's possible arguments in regionprops

[jules-vanaret]

Description:

Hi, first thank you for this package, which I have used extensively this last decade.
Would it be possible to allow extra arguments to functions passed to regionprops' extra_properties ?
Right now, these functions can have one argument (the binary prop.image) or two (prop.image_intensity if available). But passing spacing would be extremely useful.
In the current implementation, the number of arguments is checked with argspec = inspect.getfullargspec(func); n_args = len(argspec.args), which could probably give informations about the name of the arguments.
If the user is expected to give specific names to their functions' arguments, e.g

def extra_property(image, spacing):
    ....

the arguments names should be parsable and the appropriate parameters could theoretically be passed.

[jni]

👍 from me!

[jni]

(We should always pass it as a kwarg.)

[stefanv]

+1 for passing through kwargs. May need to introduce extra_prop_kwargs or similar, I haven't looked too closely. But happy to review a suggested implementation.