[sane-devel] Xsane notes

[Henning Meier-Geinitz]

Hi,

On Wed, Nov 06, 2002 at 08:05:51PM +0200, Juhana Sadeharju wrote:
> Feature suggestion:
> Are the gamma/look-up tables (of some scanners) as wide as the
> internal precision?

In hardware, yes. E.g. The Mustek SCSI Pro and Scanexpress models use
12 bits of gamma per color. It's not implemented in software, however
(see messages posted earlier).

> If a scanner has greater internal precision
> but only 8-bit output precision, then I guess the look-up tables
> could be used for dynamic compression for the 8-bit transfer.

That's how it works. Only that the mustek backend doesn't export the
12 bit gamma table to the fontends.

> The full precision would then be recovered in driver or in
> application.

How? You have a table that reduces 4096 different values to 256. How
do you want to revert that procedure? On the other hand, some scanners
provide 12 (or 16) bit output directly.

But maybe I didn't understand you correctly.

> One would have to scan a preview, compute the
> look-up tables, and do the final scan with the computed look-up
> tables. If also enchangements are done, they are also incorporated
>  to the look-up tables.

That's an issue for the backends I guess.

> Bug: Gamma etc. settings were autoadjusted after acquiring the preview
> even I had unchecked "Autoenchange gamma" and "Autocorrect colors"
> Setup-options.

I have never seen this for my scanners. But I'm using xsane 0.88 so
maybe it was an issue with earlier versions.

> Bug: In "Save" scanning mode, with Type "PNM", with filename "123.pnm",
> the saved file is named as "123.pnm.pnm" instead of the correct "123.pnm".

Doesn't happen here with 0.88.

> I would also point out that gqview, a good image viewer, cannot
> load the pnm files produced by xsane.
> The following image is show incorrectly as of the size 14x96.

Then I guess gqview has a bug. When I try gqview with xsane pnms, it
crashes (segmentation fault). As all the other viewers show the image
correctly, I think it's gqviews fault.

If I remove the comments from the pnm file, gqview can show it. The
comments are allowed in the pnm spec.

Bye,
  Henning