Re: [hylafax-users] Receiving a color fax

[Blas Rodriguez Somoza <blas@xxxxxxxxxxxxx>]

Hello Lee

Lee Howard wrote:

> Blas Rodriguez Somoza wrote:
>
> > 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. 

OK

> Are you at all in position where you'd like to work on some code in 
> libjpeg and libtiff?
I'm working on it.

I get tiffcp working for the ITULab -> RGB conversion.

I'm trying now to allow also tiffcp RGB->ITULab & RGB->YCbCr conversions.

I'll send the new patches as soon as I finish it.

> Thanks,
>
> Lee.

Regards
Blas


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