AVIF conversion with WEBP fallback

Quick PoC of an image effect with fallback format. Setting to NR for feedback on the approach, please don't send it back for tests/lint/CR etc.

Added a test for when AVIF is supported and another test for the fallback. Added a draft CR. This is ready for review.

Could the IS get some love. Wouldn't this be considered an API change?

Wonder if a CR is required?

Updated the IS to hopefully make it clearer. There is already a CR, are you suggesting it might not be necessary? I think it is useful.

Re #5:

Wouldn't this be considered an API change?

It's a new plugin, not a change to an existing one, so no breakage here. You could argue the change to the protected function in GDToolkit is a BC break, but plugins are considered internal and it's a protected method as well, so I don't think it's an issue.

I find it good/handy feature with CR)

Moreover AVIF is specifically good for big sizes with fallback

Moreover AVIF is specifically good for big sizes with fallback

Not necessarily in this issue, could maybe be a follow-up, would we want to consider some kind of configurable filesize threshold where below a certain point we always skip AVIF and use webp instead? Have seen various discussions that decoding AVIF in the browser is a lot more expensive than webp, which can undo the bandwidth savings with smaller images.

Opened up 📌 Consider falling back to webp based on filesize Active for that discussion.

One comment on the MR.

Switched to keyvalue instead of state

Looks good.

Sorry for asking, maybe it is obvious, but when we added webp format and possible conversion to core and image styles ( 📌 Add webp image conversion to core's install profile's image style Fixed and 📌 All core install profile image styles should include webp conversion Active ), we have not added any fallback. Was webp available in all PHP installations at that time? If not, are we sure that now when avif will not be available, webp will be?

@poker10 I am fairly sure that PHP installation support was widespread when webp was added to core. imagewebp from the gd library has been available since PHP 5.4 according to https://www.php.net/manual/en/function.imagewebp.php so theoretically that means it was everywhere.

However there was also an issue that older versions of osx, from around 2015 and earlier would not render webp, regardless of browser. This delayed us enabling webp by default in image styles in core until some time during Drupal 10. So we had it available as an option for a long time before then.

With AVIF it has been somewhat the opposite, in that all the browsers we care about supported it before php did. So once we do this issue, we should be able to convert the default image styles in core and Drupal CMS over, give or take the size considerations in the follow-up.