proposal: image: support 16-bit gray and alpha (so 8-bits each)

[kylepl]

Proposal Details

My use-case is around trying to write a PNG that has a gray channel and alpha channel.

I see the PNG reader supports reading the Gray + Alpha style, but it seems this is not supported as an output type.

It may be worth pairing with a image.GrayA type, and a new model.

If it generally seems reasonable, happy to dig into the details more.

Thanks!

[seankhliao]

it seems to be decoded into NRGBA, is that not sufficient for output?

[kylepl]

Perhaps I misunderstand, but that is RGBA but without alpha pre-multiplied?

The goal of this would not be increase expressivity, but just decrease space, but doing 16-bits if only alpha and colour are needed.

That being said, I believe my use-case for this is no longer needed, so I'm going to close this.