Add support for ISOBMFF Files (AVIF, HEIF, CR3)

[cryptomilk]

Describe the bug

Hello!

I've started to add support for the AVIF file format [2] in darktable using libavif [1]. I've worked with the maintainer so that it works nicely with cmake.

However I'm not able to load the image file in darktable, because exiv2 is not able to read the exif data and then fails. You can find my darktable code here [3].

If you need help or want to do some pair programming, let me know. It isn't hard to just read the exif data blob.

[1] https://github.com/AOMediaCodec/av1-avif
[2] https://github.com/AOMediaCodec/libavif/
[3] https://github.com/cryptomilk/darktable/tree/master-avif

[cryptomilk]

I've finished the implementation and can export and import AVIF images now!

[cryptomilk]

AVIF support landed in master and will be available with 3.0.1.

[boardhead]

Perhaps I'm missing something (likely), but the latest update I see to master was 20 days ago.

[cryptomilk]

I'm talking about darktable master -> https://github.com/darktable-org/darktable

[boardhead]

Ah

[novomesk]

I have a question for exiv2 developers:
Would you allow another library as dependency to support this feature?
Or the code must be completely independent, without additional libraries?
If external dependency is possible, then read-only support should be trivial. After calling avifDecoderParse() in libavif, size and metadata are available already (pixel data were not decompressed yet).

[D4N]

I have a question for exiv2 developers:
Would you allow another library as dependency to support this feature?

I have no objections to additional dependencies, provided that they are sane to build, relatively stable and don't drag us into a licensing nightmare like HEIF does.

Or the code must be completely independent, without additional libraries?

No, we have already some dependencies for reading well known formats.

If external dependency is possible, then read-only support should be trivial. After calling avifDecoderParse() in libavif, size and metadata are available already (pixel data were not decompressed yet).

Sounds good. So how is the licensing & patent situation around AVIF?

[cryptomilk]

AVIF is a royalty-free codec. The patents are free to use. I've added libavif to openSUSE and currently working to get it into Fedora.

[boardhead]

Note that AVIF is nearly identical to HEIF as far as structure and metadata is concerned.

[novomesk]

Here is an example how to print EXIF and XMP metadata from .AVIF file using libavif:
avif_metadata.cpp.txt

How to compile:
g++ avif_metadata.cpp -lavif -lexiv2 -o avif_metadata

How to use (example):
./avif_metadata Tomsk_with_thumbnails.avif

Example of the output:

[Tomsk_with_thumbnails.avif],   1280x720        8 bit   images: 1
EXIF data length: 58 bytes
Exif.Image.Copyright                         0x8298 Ascii      31  https://www.elecard.com/videos
No XMP metadata in Tomsk_with_thumbnails.avif

Test file(s) download:
https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles/Microsoft

My plug-in for GIMP 2.99 is able to save XMP metadata too. Windows installer here: https://www.reddit.com/r/GIMP/comments/f6ro3q/gimp_2991_for_windows_64bit_with_avif_support/