It's absolutely possible. Browsers even routinely pause playback when images aren't visible on screen.
They just don't have a proper UI and JS APIs exposed, and there's nothing stopping them from adding that.
IMO browsers are just stuck with tech debt, and maintainin a no-longer-relevant distinction between "animations" and "videos". Every supported codec should work wherever GIF/APNG work and vice versa.
It's not even a performance or complexity issue, e.g. browsers support AVIF "animations" as images, even though they're literally fully-featured AV1 videos, only wrapped in a "pretend I'm an image" metadata.
I wish browsers still paused all animations when the user hits the Esc key. It's hard to read when there are distracting animations all over most pages.
They just don't have a proper UI and JS APIs exposed, and there's nothing stopping them from adding that.
IMO browsers are just stuck with tech debt, and maintainin a no-longer-relevant distinction between "animations" and "videos". Every supported codec should work wherever GIF/APNG work and vice versa.
It's not even a performance or complexity issue, e.g. browsers support AVIF "animations" as images, even though they're literally fully-featured AV1 videos, only wrapped in a "pretend I'm an image" metadata.