[sane-devel] Backend calibration data storage...

[Gerhard Jaeger]

On Mittwoch, 20. August 2003 00:33, Matthew Duggan wrote:
[SNIPSNAP]
> Hi,
>
> For the canon_pp backend we received two types of calibration
> information: a gamma curve, the format of which we didn't quite
> understand (but it works good if you just feed it back to the scanner
> later), and light & dark current readings for the LIDE LED/sensor
> combo.

Good hint, 'll check the code

>
> Without the light/dark current value, the scanners produce nasty streaky
> images.  Without the gamma curve the scanners produce blue ugly or
> yellow images, depending on the model.
>
> The backend saves both pieces of calibration information in a configurable
> location which defaults to ~/.sane/canon_pp-calibration-portname if no
> setting is given.  The setting can be changed on a per-port basis in
> canon_pp.conf.  I don't mind changing that if need be, but I think we
> should try and be consistant with this.  I decided that making a
> configurable calibration file was most useful because it allowed a
> multi-user system to take advantage of only having to calibrate once.

Good idea...

>
> The driver should be robust in loading this file and fall-back to
> calibrating in memory, although it's a rather slow process so users
> will want to avoid it if possible.

Well, the fall-back will be the current default behaviour: recalibration with
each scan ;-)

Thanks for all the replies...
  Gerhard