After only a quick glance at your code, I'd try to tackle it by wrapping my own interface around the different image types (which you could argue the image standard lib should've already done for you). The interface will define CreateWeights and Resize operations. Each implementing type will consist of a struct with an embedded field of each image type you're handling, and passthrough calls to the underlying function you need. This way, your resizing logic can be implemented in one place.

The constructor might be harder to abstract as a single thing since there are variations for each image type... but that's the gist of how I'd tackle it with all of my 10 minutes of experience with your code :-) If this approach is workable, it should end up being clean and testable IMO.

Image allows you to do this more or less. The problem to be solved here is that if you write the resize logic just once, you are accessing pixels from the image via the interface in a tight loop, and most of the time taken by your image resizer is the overhead of that access.

Interesting, you have a point actually. I would have thought that the performance cost of calling through an interface would be negligible, but I'm wrong about that:

https://github.com/golang/go/issues/20116

The issues linked at the end there are interesting reads, and maybe they'll do something about this by Go 1.11.

Having said all that, will an implementation of your code with generics be all that much faster? Or slower? Of course, those are not answerable questions in practice with today's tools :-)

Go 1.11 is already feature freeze and it doesn't seem likely.

> Having said all that, will an implementation of your code with generics be all that much faster?

Likely yes. If generics are implemented via monomorphization, then you can avoid the overhead of virtual calls necessitated by interfaces.

It is possible that the compiler could become smart enough to devirtualize calls through interfaces.

Pretty sure devirtualization is a whole program optimization in the general case, and I don’t see the Go dev team Pershing that in the next couple of years.

> I don’t see the Go dev team Pershing that in the next couple of years

Agreed. But if I didn't mention it, I'm sure someone would have felt obligated to respond with a "well actually..."