[sane-devel] Scanning for fax - resolution problem

[Frank Millman]

Hi all

I have got a scanner and fax modem working perfectly on Windows. I am trying
to move them over to a new Fedora 10 server, using sane (scanimage version
1.0.19) and hylafax+ (version 5.2.8).

I am battling with getting a suitable tiff file for faxing.

The scanner is detected as a Plustec OpticPro U24. The test page I am trying
to fax is an A4 pre-printed form, where the printing is light-blue on white,
and the form is completed in handwriting. Windows has no problem in scanning
and faxing this form.

Initially I did this -

    scanimage --mode Gray --resolution 200 --format tiff -x 215 -y 297 |
sendfax -n -m -d 1234567

It worked, but the fax came out on the other side with poor resolution.

Then I tried writing the image to a file, using -

    scanimage --mode Gray --resolution 200 --format tiff -x 215 -y 297 >
/home/frank/test.tif

The size of the file created is 3.9mb. If I then do the following -

    sendfax -n -m -d 1234567 /home/frank/test.tif

it sends the fax ok, but with the same problem. 

I enquired on the hylafax list, and got the following response -

"
My guess is that the image isn't right for direct FAX (T.30) sending, and
the ghostscript middle-man is the culprit.

You can see the tiff2fax command executed in syslog if you turn up faxq
logging, and running it by hand (and with -x) will show you the GS running
to squash the bad-sized tiff to the right-sized tiff (and then you can
verify that it's the GS making the right-sized tiff look bad).
"

I did this, and can confirm that, using the tiff file of 3.9mb as input,
tiff2fax creates a tiff file with a size of 140kb, with the bad resolution.

I also got the following suggestion -

"
Another option would by to try and get SANE to scan to the right format, I
think your best bet is to try and get it to match:

Horizontal: RES of 204(pi), 1728 pixels wide *exactly*
Vertial:    RES of 196(pi), variable length (as long as your receiver
accepts it,
                 otherwise around 2150 - 2300 pixels for letter/A4
"

I tried scanimage with lower resolutions, but that resulted in an image with
a very dark background, virtually unreadable.

I tried scanimage with --mode LineArt, which worked, but the scan lost a lot
of detail, so that is not a solution.

I don't know what else to try. Any suggestions will be much appreciated.

Thanks

Frank Millman