[sane-devel] Canon LIDA 20 (plustek) scan quality

[Gerhard Jaeger]

On Thursday 13 January 2005 04:12, Alvaro Figueiredo wrote:
> On Wed 12 Jan 2005 08:51, Gerhard Jaeger wrote:
> > Hi,
> >
> > the pictures are too bright. You need to tweak the threshold
> > for the binary stuff. This is controlled by the option
> > --brightness
> > which goes from -100 (completely black) to 100 (completely
> > white). The default setting is 0. You might try -20 in your case!
> >
> > I'll do some checks here.
> >
> > Ciao,
> > Gerhard
> >
> 
> Hi,
> 
> I tried several values to the option --brightness. The scan quality 
> improved a lot! The best result that I got was using the value -95. 
> Seems that I need another scale.
> 
> After that, the image center got ok, while its sides ended dark. 
> Then, I included the option --warmup-time with value 0 and the 
> darkness on borders reduced.
> 
> The resulting images are doc1095.pdf, doc2095.pdf and doc3095.pdf. 
> The script scandocument was employed to generate these. All files 
> was published on
> 
> http://alvarof.freeshell.org/sane/
> 
> if you wish to see them.
> 
> I think that my immediate problem was solved. But, tell me if you 
> want to do any test. I would be glad to help.
> 
> Thank You by your time.
> 
> > On Wednesday 12 January 2005 02:41, Alvaro Figueiredo wrote:
> > > At Tue 11 Jan 2005 06:25, Gerhard Jaeger wrote:
> > > > Hi,
> > > >
> > > > On Tuesday 11 January 2005 05:41, Alvaro Figueiredo wrote:
> > > > > Hi, all.
> > > > >
> > > > > I recently bought a Canon LIDA 20, a USB scanner. It readly
> > > > > worked on my Linux 2.6 box, but its scan quality is really
> > > > > much worse than Windows 98 driver's scan output. It is a
> > > > > dual boot box.
> > > > >
> > > > > I am scanning regular text documents, like the sample
> > > > > bellow.
> > > > >
> > > > > scanimage --resolution 300 --mode Binary -x 210mm -y 297mm
> > > > >
> > > > > The Windows output is almost perfect, like a photocopy. The
> > > > > sane's output seems to have much less resolution and misses
> > > > > some portions of text that is not black. I am using the
> > > > > same mode (lineart) and resolution (300dpi) on Linux / sane
> > > > > and Windows. I can send both outputs, if anyone request it
> > > > > (near 150k each, in PDF).
> > > >
> > > > please send it to me.
> > >
> > > I made available three documents scanned on Linux (sane) and on
> > > Windows (manufacturer's driver). They are doc1???.pdf,
> > > doc2???.pdf and doc3???.pdf (??? is lin or win). I did ran a
> > > sample with debug enabled and published it all at:
> > >
> > > http://alvarof.freeshell.org/sane/
> > >
> > > > > I have no scanning experience, but I had tried almost all
> > > > > options of scanimage without significative improvement.
> > > > >
> > > > > Am I missing something, here?
> > > >
> > > > Probably not.
> > > >
> > > > > Follow some system information.
> > > > >
> > > > > scanimage --version
> > > > > scanimage (sane-backends) 1.0.14; backend version 1.0.14
> > > >
> > > > you might update to 1.0.15.
> > >
> > > My Linux distro uses RPM, and I already keep it updated. I will
> > > try upgrade sane later on, with alternative packages.
> > >
> > > > > scanimage -L
> > > > > device `plustek:libusb:001:004' is a Canon
> > > > > N670U/N676U/LiDE20 USB flatbed scanner
> > > > >
> > > > > sane-find-scanner
> > > > > found USB scanner (vendor=0x04a9 [Canon], product=0x220d
> > > > > [CanoScan], chip=LM9832/3) at libusb:001:004
> > > >
> > > > Could you please to the scan again, enabling the debug
> > > > output, and send me that too? export SANE_DEBUG_PLUSTEK=20
> > > >
> > > > Ciao,
> > > > Gerhard
> > >
> > > I did not scanned color pictures yet. I do not know if it
> > > presents some anomaly.
> > >
> > > Please, let me know if I may help you with more information or
> > > if I could make more tests.
> > >
> > > Thank You by your attention.
> 
> -- 
> Alvaro Figueiredo
> alvarof@freeshell.org

Hi Alvaro,

from the tests you made, we can see, that the binary scans seems still to be too
bright. I will do some tests here on my LiDE30 and also on some other devices,
maybe the settings for the binary-modes are completely wrong :(
It seems, that this mode is rarely used...

Thanks for the tests and pix.
Gerhard