add support for the AVIF, HEIC and HEIF formats

[bu6n]

This PR adds support for the AVIF, HEIC and HEIF formats.

These 3 formats have in common that they use the HEIF container format specified in ISO/IEC 23008-12.

https://nokiatech.github.io/heif/technical.html also summarizes the format quite well.

The MIME types and variant types (file extension) for HEIC and HEIF are based on sections C.2 and D.2 of the ISO specification:

[...]

[...]

A HEIF container can contain multiple images, so I kept the logic as in :ico (take the size of the largest image).

The size of an image is found in the ispe box:

Examples here: https://mpeggroup.github.io/FileFormatConformance/?query=%3D%22ispe%22

This is also valid for AVIF per the specification: https://aomediacodec.github.io/av1-avif/latest-approved.html#image-spatial-extents-property

If you find the approach ok, I could add some tests. I have tested it with some images I have found online and compared the results with exiftool, but improvements are probably still possible.

Let me know what you think.

closes #12

[rNoz]

Thanks for this, @bu6n. Great addition. Yes, it seems a proper approach mimicking the style of the previous ones, so be sure you add enough proper tests and check coverage to be sure ~100% of new code is tested. Checking the code, performance should be close to its optimal, so, I won't worry about doing benchmarks again for these new formats. Nevertheless, if you think about any optimization while doing test coverage, feel free to try and let me know (benchee could help for quick verifications).

[nozalr]

Hey @bu6n I am adding you as collaborator to be able to review a future PR.

I have been studying this today, since it has been untouched for some months, as tests + enough code coverage of the new functionality would be required. However, as I started creating tests, I have seen that it is not extracting the proper height:

$ convert tiff/layers.tiff heif/layers.heic

$ hexdump -C heif/layers.heic | head
00000000  00 00 00 1c 66 74 79 70  68 65 69 63 00 00 00 00  |....ftypheic....|
00000010  6d 69 66 31 68 65 69 63  6d 69 61 66 00 00 01 6b  |mif1heicmiaf...k|
00000020  6d 65 74 61 00 00 00 00  00 00 00 21 68 64 6c 72  |meta.......!hdlr|
00000030  00 00 00 00 00 00 00 00  70 69 63 74 00 00 00 00  |........pict....|
00000040  00 00 00 00 00 00 00 00  00 00 00 00 0e 70 69 74  |.............pit|
00000050  6d 00 00 00 00 00 01 00  00 00 22 69 6c 6f 63 00  |m........."iloc.|
00000060  00 00 00 44 40 00 01 00  01 00 00 00 00 01 8f 00  |...D@...........|

$ identify heif/layers.heic
heif/layers.heic HEIC 130x42 130x42+0+0 8-bit sRGB 1467B 0.000u 0:00.002

$ mix test
  1) test force - heic disk image - #seems? #type #info (ExImageInfoTest.Images.HEIFTest)
     test/ex_image_info_test/images/heif_test.exs:27
     Assertion with == failed
     code:  assert info(images["heic"], :heic) == {"image/heic", 130, 42, "HEIC"}
     left:  {"image/heic", 130, 64, "HEIC"}
     right: {"image/heic", 130, 42, "HEIC"}
     stacktrace:
       test/ex_image_info_test/images/heif_test.exs:30: (test)

Therefore, this requires more work. I don't close this PR, in case you want to provide all tests and fixes. Meanwhile, as I have time (I hope at some point in Jan-Feb), I will work in a new branch support-heif-format as I study what's the reason and providing the proper algorithm, tests, etc. I'll create a PR and set you as reviewer.

[bu6n]

Thanks for taking the time to check, I had put this on the shelf a bit. Would you be able to provide the whole file as an attachment so that I can further check what the problem is?

Edit: I was too fast, found the file in the test folder :)

[bu6n]

So, there seems to be more info in the clap atom, which I did not take into account. I wonder if there are more such details that I missed. It would surely help to have more test material.
I'm not sure how to parse the clap box properly, I'll need more time for that. For the example image layers.heif it should be easy, but there are more possibilities in the clap atom.

[bu6n]

I have pushed some code that should fix the test with your specific image. However the offsets in the clap atom are not taken into account. I would need an example image to test that, but I couldn't find one right now.