[sane-devel] SANE2 and filmscanners

Henning Meier-Geinitz henning@meier-geinitz.de
Tue, 24 Dec 2002 15:28:53 +0100


On Mon, Dec 23, 2002 at 04:42:35PM +0000, Jonathan Buzzard wrote:
[multipass option]
> I was thinking of a option like say SANE_NUMBER_PASSES which is an option
> list. The reason for this is that most hardware based multi-pass scanning
> offers only powers of two passes, so 2,4,8,16. I presume the reason is that
> divide by 2 (or powers of 2) is much easier in hardware as it is just simple
> shifts.

I think we can just define that it's a SANE_INT with
size=sizeof(SANE_INT). The backend author can then select the type of
constraint (range or wordlist).

> > > Batch scanning is the other. Here you might have a film or slide holder
> > > that has several separate images (or even an APS adaptor) and you
> > > just want to click a button to scan the lot. You need some way to
> > > communicate to the front end just how many images there are to scan etc. 
> >
> > Why? Just return SANE_STATUS_NO_DOCS when finished.
> True but closely related to this is the fact that scanning a single frame
> is a slow process; 10 minutes a frame is not unrealistic. Therefore
> if I only want one frame scanning the lot is a massive pain. If I have
> an APS film it will be horrendous if I just want frame 38 say. So you
> also need a way to select individual frames from what ever is loaded.
> On my scanner I have a holder for negatives, which has up to six frames,
> a holder for slides which has four and an APS adaptor which can take
> an APS film cartridge. From memory depending on which you insert into
> the scanner Vuescan offers an appropriate list to scan from.
> The backend needs some way to communicate to the front end a range
> of possible pictures to scan from, and this needs to be able to change
> while the front end is running. i.e. I might start off a session scanning
> a strip of negatives then switch to slides or APS.

I don't think that's a big problem. Just define an option like
"image-number" (SANE_TYPE_INT) and apply a range. The frontend can
then select which image to scan.

> Basically all I am doing is looking at Vuescan and thinking what do we
> need in the SANE standard to allow someone to write a free clone. One
> other thought that has crossed my mind as I am scanning in my brothers
> wedding photographs are options to do with exposure. I am not an expert
> but Vuescan is presenting me with options to "Lock exposure",
> for a "Long exposure pass" and set manual RGB/Infrared exposure.
> I would say from reading the Vuescan help that the "Long exposure pass"
> and Lock exposure option is a front end thing that is done with scanners
> that allow you to set manual exposure. In the mean time there needs
> to be some way of asking for a change in the exposure time of the CCD,
> in the standard. I am not sure how this is communicated to the scanner,
> but VueScan allows you to multiply the exposure time by a scale factor.
> So it might be 1.5 times normal etc. With the possibility that is can
> be separate for the RGB and Infrared channels (if the scanner supports
> this of course).

Well, I'll read proposals for this, but I don't have the necessary
clue to do it myself, so go ahead :-)

Keep in mind, that adding well-known options can be done even when
the SANE-2 standard is published, so it's not that urgent.