Add aspect ratio to Bluesky image embeds

[JoelOtter]

I've noticed that Bluesky (at least via the official clients) has recently stopped interpreting image aspect ratio for itself, relying instead on the information provided in the record:

Annoyingly I think the only way to address this will be to download the whole image into memory (or onto disk) and get the dimensions that way (we currently stream the image data). I'm happy to take this one, @snarfed do you have any opinions about this?

[snarfed]

Yes! We've been discussing this in snarfed/bridgy-fed#1571 . I haven't prioritized it due to the in-memory image processing, but if you want to add that - maybe with https://pypi.org/project/pillow/ ? - I'm all for it!

Also sadly Bridgy Fed uses different code to generate image blobs, https://github.com/snarfed/arroba/blob/c518924d31587dc9efa367c287c9d7d0d8654eca/arroba/datastore_storage.py#L361-L363 , but on the plus side, it should be straightforward to copy whatever we do here.

[JoelOtter]

per the Bluesky docs images are max 1MB - imo we're fine to put that in memory. I think the only reliable way to ensure a max size of image downloaded is to iterate the chunks manually in the response and append them to some buffer? My understanding is we can't rely on Content-Length headers, and some image formats like JPEG don't reliably put their size information at the start of the file.

[snarfed]

Thanks for checking! We do check Content-Length on text and JSON responses, https://github.com/snarfed/webutil/blob/6384196b72a3e4768652dc45ad55f0ff8ef9100e/util.py#L1763-L1777 , but not others. I'm not too worried about a DOS though, it's not an amplification attack, an attacker has to send us as much data as we read, and Bridgy's not a big target anyway. I'd say don't worry about it for now.

[snarfed]

...oh actually you could use FileLimiter, it does the chunked limited stream reading you mentioned: https://github.com/snarfed/webutil/blob/6384196b72a3e4768652dc45ad55f0ff8ef9100e/util.py#L1571-L1596

[JoelOtter]

@snarfed did this roll out to bridgy? My recent post didn't have the right aspect ratio unfortunately https://bsky.app/profile/joelotter.com/post/3ld45wjrxw52w

[JoelOtter]

Here it is when run locally, assume it just hasn't rolled out yet :) https://bsky.app/profile/joelotter.com/post/3ld46btlkdp2w

[snarfed]

Yes! Sorry about that, deploying now.