Created on 2022-01-10 03:27 by rouilj, last changed 2022-01-10 03:27 by rouilj.
|msg7439||Author: [hidden] (rouilj)||Date: 2022-01-10 03:27|
https://wiki.roundup-tracker.org/MixinClassFileClass defined a gzip mixin that compresses data files transparently. Could we add a similar mixin that takes an image file and converts it to avif format for storage at the same quality? This should reduce file storage needs by 66% in many cases. Issues: 1. some cases avif can increase file size. In this case, the mixin should store the original file. The mime type for the file should be the stored format: e.g. image/avif if smaller or the original image/... mime type. 2. client:_serve_file doesn't look at the accept header, it probably should. If no acceptable format is found, possible raise exception and return 406. parse_accept_header() (from roundup.rest import parse_accept_header) can do this to self.request.headers['Accept']. Consider moving parse_accept_header out of rest.py and into a general roundup/http_headers.py. Also maybe roundup/cgi/accept_language.py can join it. 3. Browsers that don't support avif. Using the <picture> tag with multiple source tags for each supported format: avif, png, jpg should work. Set the srcset="..." to .../file33/afile.jpg?@format=image/jpeg should return a jpg version of file33. It looks like the accept header includes all supported image types: e.g. chrome will download the avif type but includes image/avif, image/webp, image/apng, image/svg+xml, image/*, and */*;q=0.8. So maybe we don't bother with @format and just search for a valid hit in the Accept header. We prefer sending the stored mime type when it is supported. 4. rendering time. The conversion to jpg can be done on the fly. But this can take time. Consider caching file33 as a jpg to file33.jpg at db/files/file/0/file33.jpg. These files can be cleaned using a scheduled script to remove files either unread (atime) or older (mtime) than 30 days for example. As more browsers support avif the back conversion will be less of an issue. 5. Can this be done totally as a mixin? I think the mixin gets the client object as self. So the logic about what to convert to should be possible without changes to _serve_file. However _serve_file may need to be modified to call write_file with the modified file##.jpg name. 6. Is there some time we should not convert the file? E.G. if some analysis of the file would be damaged by converting it. Think png that trigger a remote code execution. Converting it may trigger the issue or only the original file format will support forensic analysis. For python library support, pillow with https://pypi.org/project/pillow-avif-plugin/ should support avif as source and destination formats.