Add libavif to the book in support of WebKitGTK+

[Douglas R. Reno]

Along with WebKitGTK+-2.40.0, we should add libavif to go with it.

This will also need to be tested with kimageformats (part of KF5, where it will be optional), and gdk-pixbuf (also where it should be optional).

This package will need at least one dependency - libaom. Note that libaom is just one codec though, and three others are supported (though we might be able to get away with making them optional as they need other packages). Those codecs would be dav1d, svt-av1, and rav1e.

Let's just try with libaom for now though.

[Xi Ruoyao]

Download link: ​https://github.com/AOMediaCodec/libavif/archive/v0.11.1/libavif-0.11.1.tar.gz

cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release -G Ninja .. -DAVIF_CODEC_AOM=ON -DAVIF_BUILD_GDK_PIXBUF=ON
ninja
sudo ninja install

The test suite needs gtest, which is not a part of BLFS.

libaom should be recommended (you can build the package w/o it, but I guess the result will be useless).

gdk-pixbuf should be optional or recommended (for the gdk pixbuf loader). sudo gdk-pixbuf-query-loaders --update-cache is needed after the installation.

Now I can view AVIF images in EOG. But the AVIF mime type is not associated with EOG, so I cannot open AVIF images in Nautilus. I had to use eog something.avif in a terminal.

I've not rebuilt webkitgtk with AVIF yet.

[Douglas R. Reno]

Thank you for all of the investigation on this!

Because we're talking about the ability to have other applications to have AVIF image support, I'm going to probably place gdk-pixbuf in recommended.

[Xi Ruoyao]

I've built WebKitGTK-2.40.1 with AVIF enabled. Then I can view the example at ​https://avif.io.

[Douglas R. Reno]

Fixed at acea88c358407e119be2811c25d48cba0809bb08