Hi, 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. Bye, Henning
