Re: [hylafax-users] Receiving a color fax

[Blas Rodriguez Somoza <blas@xxxxxxxxxxxxx>]

Hello

First, thank you for your quick answer.

Lee Howard wrote:

> Blas Rodriguez Somoza wrote:
>
> >    First I update libtiff and libjpeg with libtiff-3.7.4 and 
> > libjpeg-6b-36 patched. (using rpm)
>
>
> I don't understand what you're saying here by the "using rpm" part.  
> Did you get libjpeg source code (SRPM), patch it, build it, install 
> it.  Then did you get libtiff source code (SRPM), patch it, build it, 
> and then install it.  And then did you subsequently build and install 
> HylaFAX?
Yes, I get the SRPMS and then patch, build and install it.  About 
HylaFAX I install it from the rpm downloaded from hylafax.org.

I make a mistake, I don't apply the patch to libtiff-3.7.4 because I 
think it is included. I read the information in 
http://libtiff.maptools.org/v3.7.2.html too quickly.

2º Try

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.

After that I also try patching 3.7.2 with the same results, and 3.7.4 
which simply don't work.

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.

> Were you following the instructions here: ?
>
>  http://hylafax.sourceforge.net/howto/install.php#ss2.5
>
> >    Then I modify the config.ttySL0, adding Class1JPEGColorSupport: yes.
> >
> >    After that I'm able to receive a JPEG color fax and forward it to 
> > an email account.
> >
> >    I try using tif and pdf format, but I can't open the attachment.
>
>
>
> You're probably not to this point yet, but when you get here... 
> realize that the TIFF will (originally) have image data encoded with a 
> CIELAB color pallate.  I don't think that you're going to have a TIFF 
> viewer that will represent the colors properly.  So in FaxDispatch, if 
> you're going to send a TIFF image on to the recipient, you'll want to 
> convert it first with tiffcp to an RGB pallate or something that your 
> TIFF viewer will understand.
Since you mention tiffcp, I try to patch faxrcvd to make the tif conversion

+TIFFCP=tiffcp

- encode $FILE
+$TIFFCP -c jpeg:r $FILE $FILE.tif
+encode $FILE.tif
+$RM -f $FILE.tif 2> $ERRORSTO

This change only make thinks worse, I can only open the tiff with 
Photo-Lux. The colors seem completely wrong and the program report 
CIELAB photometric and the file size grows from 100 KB to 500.

Reading tiffcp routine in tiffcp.c it seems it is not posible to convert 
from CIELAB to RGB with tiffcp.

I also try with tiff2rgba and don't succeed

> Similarly, most PDF viewers are not going to be able to make sense of 
> the color pallate, either.  So when you use libtiff's tiff2pdf to 
> convert the CIELAB JPEG TIFF into PDF (which basically just is 
> replaces the TIFF wrapper with a PDF one) you'll find the colors don't 
> come out right.  That's why you'll want to use HylaFAX's tiff2pdf 
> script in the case of color faxes instead of libtiff's... because 
> libtiff's tiff2ps utility (which is used by HylaFAX's tiff2pdf with 
> Ghostscript's ps2pdf) will convert the CIELAB colors into RGB first.
>
> Yes, it is not straight-forward... unfortunately.  The ITU made it 
> this way by using an uncommon (basically fax-specific) color pallate.
>
> > DataFormat: 2-D Uncompressed Mode 
>
>
>
> My guess is that it says this because your libtiff isn't patched 
> properly yet.

With the new libtiff the reported DataFormat is the same.

> Lee.
>
>
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