On Fri, 2008-04-11 at 09:11 +0200, Giuseppe Sacco wrote:
> Hi Ross,
> libtiff (used by hylafax) currently cannot manage 16bit depth images.
> Could you please try to run "convert" with option "-depth 8" in your
> script?
>
> Bye,
> Giuseppe
>
That fixed it. Thank you very much.
There's still the question of what changes, if any, would be desirable.
I don't know if the limitation to 8 bits is documented.
file:///usr/share/doc/hylafax-doc/html/overview.html
says sendfax converts to postscript or TIFF/F.
I have never been exactly sure what TIFF/F is.
man sendfax refers simply to Postscript or TIFF, though it notes that
TIFF/F is passed on directly.
man typerules says
Only three types of files are accepted by the HylaFAX server for
trans-
mission as facsimile: POSTSCRIPT® files, PDF files, and TIFF Class
F
(bilevel Group 3-encoded) files. All other types of files must be
con-
verted to one of these three formats.
TIFF/F is not one of the formats defined by ImageMagick, though the
latter has
FAX RW Group 3 TIFF See TIFF format. Note that FAX machines use
non-square pixels which are 1.5 times wider than they are tall but
computer displays use square pixels so FAX images may appear to be
narrow unless they are explicitly resized using a resize specification
of 150x100%.
(file:///usr/share/doc/imagemagick/www/formats.html).
I've been using TIFF, not FAX, in convert. It sounds as if maybe Group
3 is the same as TIFF/F.
I tried this
$ convert -density 80.000000x77.000000 -units PixelsPerCentimeter
-geometry 1186x1646! myfile.png fax:t.tiff
$ identify -verbose t.tiff
identify: Not a TIFF or MDI file, bad magic number 5120 (0x1400).
`t.tiff'.
$ mv t.tiff t
$ identify -verbose t
identify: no decode delegate for this image format `t'.
In conclusion:
1. I wasn't exactly following the instructions.
2. The instructions are hard to follow, since sometimes they just say
TIFF and other places say TIFF/F but don't define it. If this is the
same as "Group 3" that would be good to know. Neither the online
glossary nor the online FAQ define it.
3. A more specific (and less misleading) error message would be helpful.
4. It would be nice if the server could deal with a broader range of
TIFF's. This may go against the current design of keeping such concerns
on the client, however.
ImageMagick:
5. The change in default depth for TIFF seems worth a NEWS item, or at
least something in the changelog. I couldn't find anything.
6. If group 3 is TIFF/F, it would be good to say so. If it's not, it
would be good to add it.
7. Better support (e.g., in identify and display) for the FAX format
would be helpful. It seems very odd that imagemagick can produce a file
and then not be able to interpret it.
