Add support for images with high bit depth

[linkmauve]

Hi, first of all thanks for this crate, it made AVIF support in image-rs very easy to write!

The issue is that it currently only supports 8-bit components, while modern formats like AVIF also exist in 10-bit or 12-bit depth, or even 16-bit for PNG. In practice, the output from a crate like dav1d will always use 16-bit components, with e.g. six bits left to zero and ten bits encoding the component value, for each plane.

You can find some sample files here for instance: https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles/Link-U

[fabiosky]

Hi @linkmauve,
thanks for your interest in!

We are interested as well in supporting the following features:

• 10 and 12 bit yuv support
• rgba16i and r10g10b10a2 support
• I422 format support

Those features should cover all kind of images that avif supports.

Schedule is to be planned, we think the first feature to come in the next release will be:

• conversion from 10 bit yuv (420 and 444 format) to r10g10b10a2 and rgba8 format

I will track those features in separate issues potentially related to this ticket.

Thanks,
Fabio

[linkmauve]

Awesome, thanks!

[FlareFlo]

What would it take to implement I422? Its a format i commonly encounter using Image. I'm willing to write a PR, if i figure out what is needed.