minna-pima/README.md

[WIP] minna-pima

Picture manager intended for usage with Minna.

minna-pima integrates with minna-caos to provide picture management features.

Similarly to the latter, it is intended as a companion to a single application (“the app”) that has full authority.

Features

• automatic conversion of unwanted file formats

• ThumbHash generation

• on-demand resizing and format conversion (without caching, see below)

• similarity search for finding duplicates

• CLI for administrative tasks

Notes

Pictures are not cached

minna-pima does not cache the pictures it generates on-demand. This is by design: Caching is hard and better left to tools designated for this purpose. It is therefore recommended to use a caching reverse-proxy in front of minna-pima.

Example picture upload flow

1. The client uploads a PNG file to minna-caos in cooperation with the app.

2. Because minna-caos detected that the file is a PNG image, the app decides to use minna-pima.

3. The app sends a GET /objects/ORIGINAL_UPLOAD_HASH/similar request to minna-pima:

   1. minna-pima fetches the object’s content and media type from minna-caos.
   2. minna-pima computes a perceptual hash of the picture and uses it to search its database for similar pictures.
   3. It finds two matching pictures and returns the following result:

   {
     "similar_picture_ids": ["abc123", "def456"]
   }
   

4. The app notifies the client that there are similar pictures.

5. The user decides that…

   1. the first picture is unrelated, and
   2. the second picture is a lower-quality version of the uploaded picture and should be replaced by the higher-quality version.

6. The client notifies the app of the user’s decision.

7. The app creates a new upload through minna-caos. Its ID is CONVERTED_UPLOAD_ID.

8. The app sends a POST /pictures/ request to minna_pima with the following payload:

   {
     "hash": "ORIGINAL_UPLOAD_HASH",
     "upload_id": "CONVERTED_UPLOAD_ID",
     "replaces": ["def456"]
   }
   

   1. minna-pima fetches the content and the media type of the object from minna-caos.
   2. minna-pima generates a ThumbHash and converts the picture to AVIF because PNG is not in the list of allowed source formats.
   3. minna-pima uploads the picture to minna-caos using PATCH /uploads/CONVERTED_UPLOAD_ID.

9. The app waits for the CONVERTED_UPLOAD_ID upload to finish. The new picture’s ID is also CONVERTED_UPLOAD_ID.

   A 100×100 WebP version could then, for example, be fetched from /pictures/CONVERTED_UPLOAD_ID/100x100.webp.