[sane-devel] Several comments on Canon N670U support

[Jaeger, Gerhard]

On Saturday, 5. October 2002 20:42, Theodore Kilgore wrote:
[SNIP]
> I assume the typo in Plustek-USB.txt got fixed.

Yeap ;-)

> I also assume that someone is looking for the "off" switch for the light.
> To clarify further what I said about this, let me add that, by visual
> inspection, the head appears to return correctly to its "park" position
> after a scan, but the light remains lit.

It was a backend bug, rather old one I think, but should work now.

> OK, so what in the **** is a "gamma curve"? And I assume you mean I should
> use it in GIMP after scanning?

This is a transformation that is done scanner internal or by some 
image manipulation programs. The incomming color values are used
as index within a table. The result is given back as new pixel value.
This is done internally by a lot of scanners and the table can be loaded.
(Look up table!). A gamma value of 1 means a linear transformation.
You might use xscanimage and play around with the settings. You can 
also specifiy the default values for the backend in the .conf file...

>  > > > 5. I didn't try the buttons. Do they work, too?
> >
> > No and currently not planned as it is quite not clear how SANE
> > will support this...
>
> Fine by me, actually. I can't quite see why the buttons were put on in the
> first place, taking into consideration what they are supposed to do. Their
> functions seemed to me to be very Windows-specific. Things like "scan this
> and attach it to the e-mail I am composing right now." Seems silly to us
> Linux people, doesn't it? However, we should remember that there are other
> people out there who like such features in Windows, or at least are used
> to them.
>
> Come to think of it, I do have a suggestion about such matters:
>
> If the effect of the button pushes could somehow be trapped by some
> program similar to "dumpkeys," and (for example) then mapped to start a
> specific command by some file like keytable.map then it would be quite
> easy to write script frontends which would be triggered when such a
> "signal" is received and then start up the right program (for example,
> xsane), and then do with the output what the user would reasonably
> expect... As an analogy, I just love to run mc, and on several machines I
> fixed it so that F12 is mapped to a command to start Midnight commander,
> until I finally overcame my laziness about typing mc and hitting <ENTER>.
>
> The first thing would be to have available a daemon which would trap those
> specific signals coming in over the USB port, WITHOUT having already
> started a SANE program, because the idea would be then to start SANE to do
> some specific task. Gerhard, this is not a job for either of us, I
> suspect. Certainly I am not trying to get you to drop everything and
> work on it. But perhaps somebody else will read this and think about it.
>

Well I already started to implement such a daemon, but only for the
parallel-port devices. The driver uses the proc fs to tell the outer world
about the button state. I'm not sure how to implement such a thing. I thought
that USB devices are able to send message on their own, but how to program
this I don't know. I think SANE 2.0 adresses this problem too...

Thanks for the feedback
  Gerhard