Add a generic load_file method

[pllim]

This would fix #64 indirectly, as theoretically I could implement whatever Ginga file handler I want outside of the widget, register it with Ginga, and then simply use this to open my custom file format.

https://github.com/ejeschke/ginga/blob/bbfe6455d302266c1bfd3f01bd386fbc2494f3db/ginga/AstroImage.py#L186

I can add a test if you think this is an acceptable way forward. I am open to discussions. Thanks!

Depends on: ejeschke/ginga#764

cc @ejeschke

[mwcraig]

LGTM. Maybe add a test?

[pllim]

Thanks for the review, @mwcraig ! I added a test, as requested.

[pllim]

p.s. Do I also have to open an issue in @eteq 's API thingy?

[ejeschke]

@pllim, you might want to use:

from ginga.util import loader
image = loader.load_data(filename, **kwargs)
if not isinstance(image, AstroImage):
    raise ValueError("Default index in '{}' does not reference an image".format(filename))
self._viewer.set_image(image)

[ejeschke]

Do you have a parameter for specifying HDU or some kind of index in the astrowidget load API? Because you could pass it in to idx in this load_data call.

[pllim]

This new method is meant more for ASDF than for FITS, though ideally it would work on either one if the Ginga file loader registry is set up properly.

[pllim]

@ejeschke , test is failing because ginga.util.loader is not in the stable version yet. I guess we'll have to wait for a Ginga release? p.s. There is no rush.

[mwcraig]

p.s. Do I also have to open an issue in @eteq 's API thingy?

May as well, yes

[pllim]

We agreed to do refactor this file loading API and have it be backend agnostic. See notes from Astropy Coordination Meeting 2023.