Support reading and writing of complex-valued data

[twitzelbos]

I'm proposing (and volunteering) to add support for reading and writing of complex-valued data. I like to get buy-in here before proceeding.

[nilgoyette]

I confirm that no one else is doing it (afaik)

As you know, writing is already implemented for all standard Rust types. + RGB. This leads to code duplication which I really don't like. One of our goals was to merge write_nifti and write_rgb_nifti in order to have a single write_nifti function. As always, we forgot about it :)

I would prefer not having a write_complex_nifti function alongside two other writing functions, but I understand that playing with traits in Rust is much more complex and constrained than in C++. This being said, maybe it's super simple, maybe you simply need to add Complex to DataElement, I haven't checked.

[twitzelbos]

Okay, to summarize:

• create a patch that adds the ability to write complex valued and RGB data to write_nifti
• make sure reading works the same

If that sounds good, please assign the issue to me.

[nilgoyette]

I wrote about RGB because I don't like the current design, but you don't have to "fix" anything. If your goal is to handle complex number, you're free to do only that :)

[twitzelbos]

I made some progress, and I can successfully write and mostly read everything I want. A significant change I'm making is to remove safe_transmute in favor of bytemuck, which will simplify many things.

The reason is that safe_transmute and co. make use of custom traits to signal if something is safe to transmute. In Rust, you must own either the type or the trait to be allowed to implement a trait for a type, which keeps leading to dead ends. Bytemuck has sufficient adoption that many types implement its traits, getting us out of that hole.

[twitzelbos]

Since this is merged, can we push a new version of the crate to crates.io, please?

[Enet4]

Indeed, a new version is due. I will work on it when I'm able.

[Enet4]

Done!