[argyllcms] Re: Lab values in a TIF image
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 1 Jun 2020 22:17:21 +1000
Hermann-Josef Röser wrote:
Hi,
If I save an image in Lab with 16bit/channel as TIF, the values in the three
channels range from 0 to 65535. How do I convert these to the Lab-values I
find in the reference table for my scanner target?
there is certainly some information about, for instance:
<
https://www.asmail.be/msg0055212264.html>
Note that there are 3 different TIFF L*a*b* encodings,
CIELab, ICCLab and JPEG Fax.
If you look in the Argyll source code in imdi/cctiff.c you
will find the conversions that I am using for CIELab and ICCLab.
The CIELab encodings are certainly defined in the TIFF spec. (i.e.
see TIFF6.pdf page 111), and the ICC encodings are defined in ICC
documentation (Beware of ICCV2 vs V4 Lab encoding differences though!).
See also the Adobe Photoshop TIFF Technical Notes page 12.
Cheers,
Graeme Gill.
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