does not extract EXIF metadata from JpegXL file

[breunigs]

Hi,

pointing exiftool 12.62 on a Linux at source.JPG file prints the expected EXIF metadata. After converting the image to JXL using cjxl --lossless_jpeg=1 source.JPG convert.jxl only file metadata is reported using exiftool -All convert.jxl. I am sure the jxl file still contains the EXIF, since exiv2 -p a convert.jxl can properly display it (make sure you grab an exiv2 version built with brotli).

Output for exiftool -v3:

Code Select Expand

  ExifToolVersion = 12.62
  FileName = convert.jxl
  Directory = .
  FileSize = 2059488
  FileModifyDate = 1684388358
  FileAccessDate = 1684388358
  FileInodeChangeDate = 1684388358
  FilePermissions = 33188
  FileType = JXL
  FileTypeExtension = JXL
  MIMEType = image/jxl
  + [JP2 directory]
  | FileType (SubDirectory) -->
  | - Tag 'ftyp' (12 bytes):
  |     0014: 6a 78 6c 20 00 00 00 00 6a 78 6c 20             [jxl ....jxl ]
  | + [BinaryData directory, 12 bytes]
  | | MajorBrand = jxl
  | | - Tag 0x0000 (4 bytes, undef[4]):
  | |     0014: 6a 78 6c 20                                     [jxl ]
  | | MinorVersion =
  | | - Tag 0x0001 (4 bytes, undef[4]):
  | |     0018: 00 00 00 00                                     [....]
  | | CompatibleBrands = jxl
  | | - Tag 0x0002 (4 bytes, undef[4]):
  | |     001c: 6a 78 6c 20                                     [jxl ]
  | Jpeg2000_jxlp = ...]..
  | - Tag 'jxlp' (10 bytes):
  |     0028: 00 00 00 00 ff 0a ba 5d 03 91                   [.......]..]
  | Jpeg2000_jbrd = Bq..N.4..,@.Q....rT.`(..."c.2.)..G..f...3P.C....'.3......4...QC...2[snip]
  | - Tag 'jbrd' (126362 bytes):
  |     003a: 42 71 03 88 4e cb 34 ef 81 2c 40 a0 51 00 e4 aa [Bq..N.4..,@.Q...]
  |     004a: 12 00 00 10 72 54 b6 60 28 ce ff 01 22 63 84 32 [....rT.`(..."c.2]
  |     005a: ce 29 05 ed 47 c8 10 66 a9 83 0c 33 50 ba 43 0d [.)..G..f...3P.C.]
  |     006a: d6 87 0c 27 1f 33 e0 90 83 0a 8b 1c 34 ec c0 f6 [...'.3......4...]
  |     007a: 51 43 ff fe c8 32 87 1d 77 a0 a1 e8 fe 17 63 9c [QC...2..w.....c.]
  |     [snip 126282 bytes]
  | Jpeg2000_brob = Exif.......4R........+fL*.M.^U..< K.e...U...mv..*.1.c...;.o.\....se[snip]
  | - Tag 'brob' (4619 bytes):
  |    1eddc: 45 78 69 66 1b ee 1e 11 d5 b4 1e 00 34 52 16 ce [Exif........4R..]
  |    1edec: df ef cf b6 de f0 2b 66 4c 2a 0a 4d 02 5e 55 aa [......+fL*.M.^U.]
  |    1edfc: c6 3c 20 4b 83 65 d1 aa 1e 55 ae 1d a0 6d 76 94 [.< K.e...U...mv.]
  |    1ee0c: 08 2a 8a 31 b1 63 0e b0 0b 3b f6 6f ad 5c 1a 0b [.*.1.c...;.o.\..]
  |    1ee1c: b1 1b 73 65 a2 33 73 69 74 4c b1 72 51 fe fc b1 [..se.3sitL.rQ...]
  |     [snip 4539 bytes]
  | Jpeg2000_jxlp = ...[..L.?.`.,`;..E......B.3.5.t.1.}...|R..y....Y..R...y.OPr.~.....6[snip]
  | - Tag 'jxlp' (1928433 bytes):
  |    1ffef: 80 00 00 01 e0 5b 04 10 00 4c ec 3f 1f 60 fb 2c [.....[...L.?.`.,]
  |    1ffff: 60 3b 0b a0 45 0b 90 fe 93 11 91 42 10 33 90 35 [`;..E......B.3.5]
  |    2000f: 90 74 d0 31 91 7d d0 ec d1 7c 52 9f d3 79 9a 15 [.t.1.}...|R..y..]
  |    2001f: db eb 59 e4 98 52 98 cc 94 79 95 4f 50 72 90 7e [..Y..R...y.OPr.~]
  |    2002f: 10 88 90 e4 10 36 11 a0 11 5f 91 5b 93 e0 db 93 [.....6..._.[....]
  |     [snip 1928353 bytes]
Thank you
Stefan

[greybeard]

Looks like cjxl compresses up the EXIF metadata (with the Brotli algorithm) and stores it in the "brob" box  instead of the Exif box which would presumably be uncompressed.

[Phil Harvey]

Thanks for this report, and for the example.  I'll look into this when I get a chance.

- Phil

[Phil Harvey]

Hmmm.  Unfortunately there isn't a simple Brotli decompressor module for Perl to decode the 'brob' box.  It looks like I would have to write one myself.  Edit: Found one!

My development will be hampered by this, as well as the fact that the JXL file format specification is imprisoned by the ISO. 

- Phil

[Phil Harvey]

I have a working version of ExifTool which can read the image size from partial JXL codestreams and read/write/create compressed 'brob' XMP and EXIF metadata.

I need to do more testing, but it is looking good for inclusion in ExifTool 12.63

- Phil

[Phil Harvey]

Version 12.63 is now available.  Reading/writing 'brob' metadata requires IO::Compress::Brotli to be installed.  (This is included in the Windows .exe package, but would need to be installed separately on Mac/Linux.)

- Phil