Accessing image metadata without decoding about libavif

[joedrago]

This path exists already. See the decoding sample in the readme which calls avifDecoderParse().

[joedrago]

I should clarify:

avifDecoderParse() is the function you are looking for, and it populates a bunch of members in avifDecoder prefixed with "container", which include the width, height, and depth. XMP and EXIF are also available after this call.

There is no guarantee that these values match the actual decoded image (if someone were being malicious), but they will be correct most of the time, and if they ever mismatch you can consider it an error.