Calculate hashes of images and include it in image_details field to improve image caching

[asudox]

Requirements

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Is your proposal related to a problem?

The image_details table in (for example) a getpost json response does not include the hash of the image. A hash could be used to cache images better.

I assume the link field in image_details could be used for image caching, but this would not cache duplicate images or duplicates in other instances.

Describe the solution you'd like.

A SHA256 hash would be calculated and stored when an image is uploaded to an instance. This would then be returned in the image_details table.

Describe alternatives you've considered.

None.

Additional context

No response

[Nutomic]

Images are already served with all the necessary headers for caching:

cache-control: public, max-age=86400, immutable
etag: W/"1167f-193300d43e0"

[asudox]

Images are already served with all the necessary headers for caching:

cache-control: public, max-age=86400, immutable
etag: W/"1167f-193300d43e0"

that caches the image at that unique link. if there are duplicates of the same image, this would not work.

if, for instance, the same image is uploaded again by another user (on the same instance or another instance), this wouldn't get the cached image, but make a new request to get the same image, even though the same image with the same hash is available in the image cache because the duplicate has a different link.

[dessalines]

Seems like pictrs could handle this case, maybe via redirects or something on duplicate hashes to the same image.

cc @asonix

[asudox]

Seems like pictrs could handle this case, maybe via redirects or something on duplicate hashes to the same image.

well, I guess that would save storage and solve this problem when the duplicate image is on the same instance.
however, with hashes, it wouldn't matter if that image is uploaded to instance X or instance Y, it would still work.

what you suggested could probably be another feature request for saving storage as it does not quite achieve what I meant in my feature request.