Support Picture Element

[ephes]

After wagtail now supports different image formats, it would make a lot of sense to just render <picture>-elements instead of only the srcset attribute of <img>-elements. Don't know how difficult this will be. We'll see 😇.

[thibaudcolas]

Hi @ephes, you might be aware but Wagtail now ships with a <picture> implementation built-in: https://docs.wagtail.org/en/stable/releases/5.2.html#responsive-multi-format-images-with-the-picture-tag

There are lots of possible improvements we’d like to make to this implementation, so any feedback is very welcome if there are things your package does that aren’t possible with that one.

And for this package, there’s lots of this work you could reuse if you wanted to:

• get_renditions_or_not_found allows generating or retrieving multiple image renditions in one go, as optimised as possible so this is faster than sequentially doing the same.
• The Filter class now supports defining multiple image formats in one length with a special syntax
• ResponsiveImage and Picture classes are how we generate the HTML.

All three are private APIs currently but could be made public if there’s a need.