[sane-devel] Re: snapscan & interpolation

[Bertrik Sikken]

Alexandre Abbes wrote:
> Hi I have a snapscan 310, which has an optical resolution at 300dpi.
> 
>> Thus the xsane button only proposes resolution up to 300dpi. But I 
>> know that with a good interpolation, one can scan with this scanner
>>  up to 1200dpi. Does anybody know how interpolation works? Is it a
>> job done by the scanner itself, or a soft post-prossessing that can
>> be done with gimp? Any comment welcome !
> 
> Alex
> 
> One case that I can imagine is that the scanners' CCD has a
> resolution of 300 dpi (=horizontal resolution), but can do motor
> steps with a higher resolution (=vertical resolution = e.g. 1200
> dpi).(=vertical). In that case I can imagine that it makes sense to
> interpolate to 300x1200 dpi.
> 
> Bertrik
> 
> Thanks for answer bertrik Ok, I begin to anderstand. So the
> interpolation is vertical. The motor does smaller steps, and scans at
> 300dpi, but with the steps at 1200dpi, there is a soft
> post-processing to get an image at 300x1200dpi. Is there any way with
> sane to tell the motor of the scaner to do smaller steps? I should
> get then an image 4x longer then the normal one. Alex

I made a mistake. I meant to say
"In that case I can imagine that it makes sense to
interpolate to 1200x1200 dpi."
----------------^
So what I mean is that some scanners can scan with different
resolutions in the vertical and horizontal direction. If your
scanner can also do that, it would make (limited) sense to
interpolate the horizontal resolution to from 300 to 1200 dpi
and use the native vertical resolution of 1200 dpi.
I have no idea how to do this for your scanner.

Bertrik