[sane-devel] Epson 3490

[Oliver Schwartz]

Hi,

> > If it is always the same ratio of real distance to scanned
> > distance (also for -l and -t) it is most likely that the
> > calculation of the scan area is not handled correctly. That could
> > be corrected by changing the value of pos_factor in function
> > set_window() in snapscan-scsi.c.
>
> That would seem to be the case here.

Yes, so maybe it's enough to just change that value for the 3490. It's 
set in line snapscan-scsi.c, line 810. The value is currently set to 
1600 for resolutions below 1600, 3200 for resolutions above. If your 
distances are off by 25%, try setting it to 1600/0.75 = 2130.

> > For the guy that developed the patch that didn't help, though.
>
> Hm.  Is that the guy that you say below has the scanner working for
> him, or is it someone else?

Yes. Unfortunately I've lost contact to him, i.e. he doesn't answer my 
mail.

> > I don't think that this is an unsolvable problem. It may be
> > necessary to do some deeper analysis and maybe get some USB
> > traces from the windows driver, though.
>
> How do I go about getting such traces for you (or whoever it is
> who'll likely be working on this)?

You can use usbsnoop:  http://benoit.papillault.free.fr/usbsnoop/
The files tend to get very large, so chose a very small scan area and 
a low resolution. You can send them to me in private mail.

> > Also keep in mind that the scanner seems to work for at least one
> > guy, so the solution can't be that difficult :-)
>
> I certainly hope that is the case!  What did that guy do to make it
> work? I.e. scanning over the whole area?

He developed the patch. His last mail stated it works, so I applied it 
to CVS.

> (On a side note: Is brightness supposed to work for lineart mode? 
> As it is, it tends to make Lineart mode scans too dark - things
> that are clearly (but somewhat faded) white paper gets smothered in
> black.  My UMAX Astra 1200 didn't have that problem at all.)

Yes. The parameter is called "Threshold" in lineart mode. It's 
available in the Standard Options window in xsane or as option 
--threshold in scanimage.

/Oliver