[sane-devel] Where should a backend save config data ?
Thu, 25 Jul 2002 12:12:05 +0200
Oliver Rauch, Mittwoch, 24. Juli 2002 22:07:
> You will not be able to save the data to a system directory
> because all users need write access to the file.
> Be carefull with security with such files!
I was thinking about saving the values on a per-user basis, not some sort of
global config file. As long as the user isn't scanning over a network
(saned/net), is there a problem with using the users $HOME/.sane directory
> I suggest not to save any calibration data to a file.
> The calibration data does not keep valid for a long time
> because the illumination of the lamp does change, especally
> for several minutes after the scanner lamp has turned on.
I should mention, that this is a CIS device, I can't see any difference
in the calibration values between scans(maybe over a long term of usage due
to aging of the sensor/LED rows?). The windoze driver saves all the values to
disk and avoids repeating the calibration sequence, which takes about 20
seconds (or more).
> I suggest to keep the calibration data in the memory or
> save it to a temporary file that is erased when sane_close
> is called.
That's what I do at the moment. Another approach was to use default
offset/gain/exposure values in the .conf file (optional) and only do shading
correction after sane_start is called the first time. The scanner will still
work without those values and there's also a "Calibrate before next scan" -
option to enforce calibration. The problem is, that this is a global setting
which affects all users.
> > small problem:
> > Is there a well-known location, where a backend should/could save some
> > data? I'd like to save some calibration data (shading,exposure ...), but
> > I'm not sure how to do this.
> > Should this go to $HOME/.sane ? Does this work with saned?