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

[Martijn van Oosterhout]

On Tue, May 13, 2003 at 11:31:17AM -0500, Peter Chen wrote:
> 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.

Perhaps you need to do some calibration? The HP5400 scanner has a white
strip inside the scanner which you scan first. That gives the white level
for each colour and pixel. That's then used to fix up the rest of the
image.

-- 
Martijn van Oosterhout   <kleptog at svana.org>   http://svana.org/kleptog/
> "the West won the world not by the superiority of its ideas or values or
> religion but rather by its superiority in applying organized violence.
> Westerners often forget this fact, non-Westerners never do."
>   - Samuel P. Huntington
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