[sane-devel] Why is the background of the scanned image not a constant grayscale

[Peter Chen]

Hi,

I still do not quite understand. When I tried to scan the same image using
Twain, there was no gray background. What could be the reason?

And I could not find the option to set the option brightness/contrast when I
ran: scanimage --help -d fujitsu:/dev/usb/scanner0.

Thanks,

Peter

----- Original Message -----
From: "m. allan noah" <anoah@pfeiffer.edu>
To: "Peter Chen" <peterchenn@hotmail.com>
Sent: Tuesday, May 13, 2003 8:43 AM
Subject: Re: [sane-devel] Why is the background of the scanned image not a
constant grayscale


>
> ok, a few points:
>
> 1. never, ever send someone the routing numbers on the lower edge of a
> check.
>
> 2. the gray background that you see cannot be avoided. it is the
> reflection of the wight stripe on the opposite read head. open your
> scanner, and notice the bottom read head has a white plastic stripe bellow
> it. the top read head has a wight plastic stipe above it. these line up
> when the unit is closed.
>
> 3. immediately around the check, there is a darker line. this is a shadow
> caused but the thickness of the edge of the check. there is no way to
> avoid it.
>
> 4. if you scan the check in the middle of the adf, you would need to set
> the -l to something higher, to cut off the background, then you dont have
> to deal with it. you just have to cut it off, or turn up the
> brightness/contrast to make the back completely wight.
>
> allan
>
> On Mon, 12 May 2003, Peter Chen wrote:
>
> > Hi,
> >
> > I scanned one check using the command:
> >
> > scanimage -d fujitsu:/dev/usb/scanner0 --format=tiff
> > -l 0 -t 0 -x 100 -y 200 --mode=Gray --rif=yes > ttt.tiff
> >
> > then on my Windows machine, I converted it to jpg file.
> >
> > I did not try SCSI yet.
> >
> > Thanks,
> >
> > Peter
> >
> > ps: pls also see the comments below.
> >
> >
> > ----- Original Message -----
> > From: "m. allan noah" <anoah@pfeiffer.edu>
> > To: "SANE Mailing List" <sane-devel@mostang.com>
> > Sent: Friday, May 09, 2003 1:56 PM
> > Subject: Re: [sane-devel] Why is the background of the scanned image not
a
> > constant grayscale
> >
> >
> > > 1. what mode are you scanning in, grayscale, lineart, color?
> > grayscale
> > >
> > > 2. what do you mean by layer? the fujitsu driver returns only one
frame to
> > > the front end, so there should not be a case where there is multiple
pixel
> > > data available for one physical pixel.
> > Sorry, I was not very clear. Please see the jpg file attached. You can
see
> > outside the edge of the check, there is another layer which is not
totally
> > white nor totally black.
> >
> > >
> > > 3. does this happen with other front-ends?
> > Yes, I used scanimage, and it was the same thing. Actually, I created a
> > bitmap file using the data from sane_read in my application to display
it in
> > Kylix.
> >
> > >
> > > 4. does this happen with the scsi connection instead of usb?
> > Sorry, I did not try it yet.
> >
> > >
> > > 5. could you send me directly a copy of an image where you see this?
> > Sure. Please see attched jpg file. If you need the tiff or bmp file, let
me
> > know.
> >
> > >
> > > allan
> > >
> > > On Fri, 9 May 2003, Peter Chen wrote:
> > >
> > > > Hi,
> > > >
> > > > I set up the tl_x, tl_y, br_x and br_y, scanned one image and found
that
> > > > there was another layer between the real image and the dark
background.
> > It
> > > > was a rectangle, not of constant grayscale. The scanner is Fujitsu
> > fi-4120c.
> > > >
> > > > Could somebody pls tell me how to get rid of this layer? Since when
I
> > scan
> > > > images using Twain, there is not such a layer.
> > > >
> > > > The reason that I want to get rid of the layer is I need to do some
edge
> > > > detection and deskewing. If the background is a constant black (or
> > white),
> > > > then it would be much easier to implement the algorithm.
> > > >
> > > > Thanks,
> > > >
> > > > Peter
> > > > _______________________________________________
> > > > Sane-devel mailing list
> > > > Sane-devel@www.mostang.com
> > > > http://www.mostang.com/mailman/listinfo/sane-devel
> > > >
> > >
> > > --
> > > "so don't tell us it can't be done, putting down what you don't know.
> > > money isn't our god, integrity will free our souls" - Max Cavalera
> > >
> > > _______________________________________________
> > > Sane-devel mailing list
> > > Sane-devel@www.mostang.com
> > > http://www.mostang.com/mailman/listinfo/sane-devel
> > >
> >
>
> --
> "so don't tell us it can't be done, putting down what you don't know.
> money isn't our god, integrity will free our souls" - Max Cavalera
>
>