Should we switch image formats?

[eyeseast]

We've been making GIFs of PDF pages forever, but it's an old format and there are newer, better options. Should we switch?

There are lots of choices: https://developer.mozilla.org/en-US/docs/Web/Media/Guides/Formats/Image_types

PNG feels like the obvious choice, but we should also consider WEBP or AVIF.

Legacy consideration: We'd need to add a field to the database to indicate format. Old documents aren't going to use the new formats unless they're reprocessed.

[eyeseast]

Another option: We could add a lambda fallback that generates missing images on the fly.

https://repost.aws/questions/QUlgR93MhwTSWTpMuPYCp3iQ/can-i-trigger-a-lambda-function-when-a-file-is-not-found-on-s3

[eyeseast]

The legacy viewer does hardcode .gif here: https://github.com/MuckRock/documentcloud-frontend/blob/legacy/src/api/viewer.js#L20-L27

That would be easy enough to fix, but I also don't want to touch legacy if we don't absolutely have to.

[allanlasser]

GIFs are big and lossy — PNG and WEBP have better performance characteristics.

We're skeptical of the benefits being worth the effort here. This would be worth exploration and investigation to understand the complexity of on-demand image generation, the actual performance characteristics of PNGs versus WEBPs versus GIFs, and the development cost.