Re: [hylafax-users] Receiving a color fax

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

Blas Rodriguez Somoza wrote:

> The question is that the CIELab color space is not the same that 
> CIELAB encoding. CIEL*a*b have at least three encodings CIELab, 
> ICC(Lab) and ITU(Lab).


Well, now that's particularly confusing.

> In the RFC2301 (chapter 6.2.1) there is very clear reference to the 
> encoding used in faxes :
>
> PhotometricInterpretation(262) = 10. SHORT Base color fax mode 
> requires pixel values to be stored using the CIE L*a*b* encoding 
> defined in ITU-T Rec. T.42. This encoding is indicated by the 
> PhotometricInterpretation value 10, referred to as ITULAB


Okay, so I'm with you on this now.  The PhotometricInterpretation TIFF 
tag for color faxes needs to be ITULAB (10).  Making that change in 
HylaFAX will be very easy to do, but once that's done then we end up 
with no way to use that TIFF image file... because nothing out there can 
utilize that encoding type.  So we'd have to make come corrections or 
modifications to libtiff.  It would *seem* that at least tiff2ps (via 
patched libjpeg) is doing things correctly... except that it, too, 
internally refers to the wrong name for the encoding.  Is it just a 
matter of renaming things?  In any case once we start looking at working 
on code in libtiff I get hesitant, and I simply do not know what I'm 
doing in libjpeg.  The problem being, however, that because ITULAB is 
fax-specific there just aren't many libjpeg developers that are interested.

Are you at all in position where you'd like to work on some code in 
libjpeg and libtiff?

Thanks,

Lee.


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