Is the ICC JPEG Embedding Spec Correct?

[clanmills]

Phil

I'm adding ICC profile support to Exiv2 for the upcoming v0.26 release.  I think there's an error in the ICC document:  ICC1v43_2010-12.pdf <— Annex B contains embedding spec

It says that the profile should be embedded in an APP2 Segment with the initial bytes of the data set to ICC_PROFILE\0 (12 bytes) followed by a chunk counter (one byte) and total chunks (one byte).  So, the first 14 bytes are defined.  I assume the remainder of the segment is profile data. However, from testing using iccDumpProfile, there seem to be 4 padding bytes (2 before the data and 2 after).

I've written a little script to download all your test bundles (such as Canon.tar.gz).  You have 6577 JPGs of which 92 have embedded ICC profiles.  To successfully run iccDumpProfile on these profiles, I have to strip the 4 padding bytes.

What do you think?

[Phil Harvey]

Look at section 7.2 of ICC1v43_2010-12.pdf.  The first 4 bytes are the profile size.  I think the problem here is iccDumpProfile.

If you use ExifTool to extract the profile, then the first 4 bytes output are the profile size.  These come immediately after the 14-byte header in JPEG images.

- Phil

[clanmills]

Thanks Phil, I knew you'd know.  And yes, of course, I should be using exiftool in my testing as well as iccDumpProfile.

Not good that I can't trust iccDumpProfile!  I'll report a bug to the ICC people.  I'd like an enhancement to iccDumpProfile to read profiles from stdin.  Then I can pipe the data from Exiv2 into the iccDumpProfile.  Something like:

Code: [Select]

$ exiv2 -eC- foo.jpg | iccDumpProfile -
-eC = Extract Color Profile (to foo.icc)
-eC- = Extract Color Profile to stdout
As always, Thank You for your help.

[Phil Harvey]

I don't know what iccDumpProfile has over ExifTool, but you can of course pipe to ExifTool like this:

exiv2 -eC- foo.jpg | exiftool -

- Phil

[clanmills]

Ah.  I don't know why I'm bothering with iccDumpProfile.  I'm only using it in the terminal.  It's not used by our test suite.

I feel, (English accent on) it isn't quite cricket (restore normal voice) to use exiftool in testing Exiv2.

I built iccDumpProfile a while ago and it seemed OK.  Last weekend, I discovered it no longer builds on MacOS-X 10.11.  The Apple people have changed the SDK and removed support for CMmumble APIs.  (CM = Color Murderer or something).  It's impossible to use earlier SDKs.  So iccDumpProfile doesn't even build any more on MacOS-X.  Now if only the ICC people supported and maintain their code with the diligence of you and I.  (and our modesty of course).

[Phil Harvey]

I feel, (English accent on) it isn't quite cricket (restore normal voice) to use exiftool in testing Exiv2.

Jolly good then.

(and our modesty of course).

It's easy to be modest when you're the best.

- Phil