Thank you all ! The encoding is not always D65 CieLab so how to know Lab 
encoding please ?

Envoyé de mon iPhone

> Le 27 avr. 2022 à 14:51, [email protected] a écrit :
> 
> Just check bitspersample. You can fetch the decoded pixels from the
> file in the usual way, for example with TIFFReadScanline().
> 
>> On Wed, 27 Apr 2022 at 13:07, Sylvain Ard <[email protected]> wrote:
>> 
>> OK thank you and for retrieving the RAW values of the channels and how to 
>> know if the ranges are 0 - 255 or 0 - 65535 please ?
>> Sylvain Ard
>> 0549507724
>> 0778380991
>> [email protected]
>> http://sylvain-ard.fr
>> Entreprise individuelle SIRET : 80079243400022
>> Appt 26 Bât A Résidence Le Patio
>> 83 rue de la Bugellerie
>> 86000 Poitiers
>> 
>> 
>>> Le mer. 27 avr. 2022 à 14:05, <[email protected]> a écrit :
>>> 
>>> Hello Sylvian,
>>> 
>>>> Le sam. 23 avr. 2022 à 21:59, Sylvain Ard <[email protected]> a écrit :
>>>>> 1 : I want to know with libtiff the LAB encodage of the TIFF ie CIELAB, 
>>>>> ICCLab ou JPEG Fax
>>> 
>>> It's D65 CIELAB.
>>> 
>>>>> 2 : I want to know the bits number per LAB channel by libtiff
>>>>> 3 : I want to get the RAW LAB channels values of a pixel with libtiff
>>> 
>>> It's usually 8 or 16 bits unsigned, with L 0 - 100 and ab +/- 128 all
>>> scaled to 0 - 255 or 0 - 65535 in the obvious way.
>>> 
>>> John
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