Re: [hylafax-users] Receiving a color fax

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

Blas Rodriguez Somoza wrote:

> I get libtiff-3.7.1 and libjpeg-6b-34 SRPMS (the ones included in FC4) 
> and patch the two.
> After that I can open the tiff attachment.
> I found two programs which open the resulting tif, Photo-Lux and 
> ViewOne. With the two the result is exactly equal, the image content 
> is OK but the color balance are wrong, white appears as light blue.


The color balance is wrong because the TIFF viewer doesn't know how to 
represent the CIELAB color pallate.  This is not surprising.  The CIELAB 
color pallate is, as far as I'm aware, only commonly used in faxes (as 
uncommon as a color fax is).

> I modify the original patch to be able to apply it to 3.7.2 and 3.7.4. 
> I can send the modified patches to the list if you want.


If you like you can post them to the libtiff Bugzilla.  My guess, 
however, is that libtiff will not make any commits on this until the 
libjpeg folks commit the patches on their end, as the libjpeg changes 
are requisite for the libtiff changes to be useful at all.  And, if you 
ask me, libjpeg development at the IJG is dead... even with the new 
maintainer.  (Notice that the maintainers of libtiff now maintain their 
own fork of libjpeg because the development at the IJG is so dead.)

> Since you mention tiffcp, I try to patch faxrcvd to make the tif 
> conversion


Indeed, you are correct.  tiffcp won't work.  I didn't modify tiffcp for 
CIELAB.  So that leaves only tiff2ps.  And I don't think that PostScript 
handles compressed image data, so you'll end up with a very large ps 
file after tiff2ps gets done with it.

> With the new libtiff the reported DataFormat is the same.


I just tested here myself sending a color fax from a Brother MFC-3100C 
to Hylafax 4.2.4.2 using a Class 1 IAXmodem.  Here is the session log, 
if you're interested:

 http://hylafax.sourceforge.net/examples/c000000608

Here is the 'faxinfo' output on the received TIFF file:

fax000000295.tif:
   Sender: 3604278160
    Pages: 1
  Quality: Fine
     Page: North American Letter
 Received: 2006:01:24 21:12:53
TimeToRecv: 2:27
SignalRate: 9600 bit/s
DataFormat: JPEG Full-Color
ErrCorrect: Yes
  CallID1: fax
  CallID2: Fax
  CallID3: 0124
  CallID4: 2112
  CallID5: 400
  CallID6: <NONE>

Here is the TIFF file itself:

 http://hylafax.sourceforge.net/examples/fax000000295.tif

To view this fax I first converted it to PostScript using libtiff's 
tiff2ps.  The resulting file was 22MB (!).  Then I used Ghostscript's 
ps2pdf to convert it into a PDF.  The resulting file was 174KB.  You 
should be able to view it.  Here it is:

 http://hylafax.sourceforge.net/examples/fax000000295.pdf

If you would like to use the libtiff and libjpeg SRPMs that I have been 
using they are here:

 http://sourceforge.net/project/showfiles.php?group_id=148904

If you would like to spearhead some development work to get libtiff's 
tiffcp to properly handle CIELAB, then that would be wonderful.

I hope this helps.

Thanks,

Lee.


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