[sane-devel] HP7650 (HP5590 back.) scanner works, quality bad - website states "complete"

[Olaf Meeuwissen]

Daniel Schäfer writes:

> Hi,
> I have an HP7650 scanner which should work out of the box
> (see http://www.sane-project.org/sane-mfgs.html#Z-HEWLETT-PACKARD)
> Status: complete
>
> I'm really afraid that I have to say, that this information seems to be 
> wrong.
>
> 1. Duplex:
> Duplex doesn't work really well as the front and back side of the 
> document are stored inside a single file/image. I already read that this 
> is because the scanner doesn't expose a "page turned" information.
> But I discovered that the information is buried in the image data! The 
> right last pixel column is normally black, gray when page is turned and 
> white when there is no more document. I have a very simple octave script 
> which generates two image files from a single Duplex-ADF image. (I can 
> contribute if wanted).

It'd be a lot nicer if the backend could take this information into
account and start a new page when that column changes from black to grey
(and vice versa).  Also, I guess that that last column should be removed
from the image data.

> [...]
> 3. Scan area
> The usefull scan area is limited at the left and top side. If i put the 
> document right to the borders, the scanned image is missing like 0.3mm 
> even with x and y offset settings to 0.

I have seen similar with EPSON flatbeds and that was a mechanical issue.
When I actually aligned the document with the markings on those borders
(which were ever so slightly towards the right and bottom) everything
was fine.  Could be the same here.

Basically, you are assuming that the 0 offsets you pass the backend
correspond to the physical borders.  That may not be the case.

Hope this helps,
-- 
Olaf Meeuwissen, LPIC-2           FLOSS Engineer -- AVASYS CORPORATION
FSF Associate Member #1962               Help support software freedom
                 http://www.fsf.org/jf?referrer=1962