Test file sources:

* https://github.com/link-u/avif-sample-images
* https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles
* https://github.com/AOMediaCodec/libavif/tree/main/tests/data
* https://colinbendell.github.io/webperf/animated-gif-decode/avif.html
* https://0xc0000054.github.io/pdn-avif/using-image-grids.html