image: add RGBA64Image interface [freeze exception]

[nigeltao]

Background

Issue #44808 proposes adding an image.RGBA64Image interface and related code to the standard library.

The proposal was marked likely accept on 2021-04-29.

(Some dates may be out by ±1 day, because when various web sites provide a time stamp, it's not always obvious what time zone it's in).

cl/311129 was sent out for review on 2021-05-02. This change is (+292 -0) lines of code. It only adds new interfaces and methods to satisfy them. It does not modify or delete existing code.

Go 1.17 entered release freeze on 2021-05-04.

That proposal was accepted on 2021-05-06.

Unfortunately, the reviewers didn't see that the proposal was accepted until over a month later, 2021-06-17, yesterday.

The reviewers have since given "Code-Review +2", with some minor suggestions, some conditional on whether this still lands in Go 1.17.

Freeze Exception Request

I am asking for a Go 1.17 freeze exception, following the process posted to golang-dev.

@dmitshur

[dmitshur]

Thanks for making a freeze exception request. I'll discuss this with the @golang/release team tomorrow, and we'll try to make a decision by then.

[dmitshur]

We've discussed this exception, and it is approved. This will need to be mentioned in the release notes (#44513), which can be done in the same CL or a follow up one. Please proceed and get everything submitted before RC 1 (which won't happen before July).

I've updated the milestone of issue #44808 to Go1.17, closing here.