[sane-standard] More device properties

[Olaf Meeuwissen]

abel deuring <adeuring at gmx.net> writes:

> Hi all,
>
> Étienne Bersac wrote:
>
>> Thanks for you comments. There are very useful.
>> 
>>>   - alignment of original to scan origin or not (centered feeds)
>> 
>> That's an important point. SANE should provide a "adf padding" option or
>> similar.
>
> Some hints how the alignment of the paper width in the feeder
> affects the scan window settings may be useful, but I think this is
> too simple.
>
> I see several "scanner parameters" that can affect the scan window
> settings:
>
> (1) the paper can be centered/left aligned/right aligned in the
>     feeder
> (2) some scanners know about the parameters "page width" and "page
>     length"
> (3) the origin of the scan window coordinates is fixed, or it is at
>     the "corner" of the selected page size.
>
> Another question is, if a frontend really needs to know about all
> these details: If a user does not properly adjust the paper width of
> the  feeder, the scan results will anyway be a bit messy. And if we
> assume that the feeder is properly aligned, I think that (1) is no
> longer important.

In the most extreme case a frontend doesn't need to know anything:
just scan at the default settings.  The thing is that some users want
to do things that require access to the very last little bit of
configurability.  That doesn't automatically imply that every little
option should be in the standard, of course.

>>>   - limiting scan area to page size
>> 
>> This can be done via {tl,br}-{x,y}. Isn't it ?
>
> right.

True, but I was thinking of an advanced boolean option where user
could turn this behaviour off if they want to.

>>>   - rotation of original
>> 
>> Imo, this is post processing, device/sane/backend should not care this.
>
> right.

On second thought, this option is not limited to ADF.  However, if the
hardware can do rotation of the image data, there should be an option.
I know of several scanners that can do mirroring in hardware.  Why
have the backend or frontend do this if the hardware can?

>>>   - "ADF preview" (feed first page, do a preview scan, leave it on the
>>>     scan area so the user can fiddle with whatever other options before
>>>     starting a scan of a 100 page document.  You may even want to allow
>>>     for repeating the preview with the same page.)
>> 
>> That makes sense.
>
> ...only for some, if any, ADF scanners. Those ADF/flatbed scanners I
> know work a bit different in ADF mode: They do _not_ place the paper
> on the glass pane and then move the scan head across the pane;
> instead they acquire the scan data while the _paper_ is moving,
> while the scan head stays at a fixed position. This is faster, since
> the paper must be moved anyway in ADF mode, so first placing the
> paper on the glass pane and then scanning it in "flatbed mode"
> simply requires additional time.

I have experience with both types.  The higher end EPSON scanners (A3,
business market) pull the page onto the bed.  If you scan A4 oriented
so that two pages fit on the bed you get the situation where the first
page results in a single page on the bed and all following pages will
have _two_ pages on the bed.  Ideally, you would only scan the page
that was just put on the bed and ignore the rest.  Of course, media
size detection is a prerequisite to get this done.

Anyway, the idea is that if some ADF unit puts pages on the bed
instead of pulling them over the scan head then for those units
previewing might make sense.

>> So, I propose the following options add:
>> 
>>       * simplex/duplex document
>>               * name: "adf-duplex"
>>               * title: "Duplex/simplex"
>>               * desc: "Wether the document in the ADF is duplex or
>>                 simplex."
>>               * type: string enum
>>               * values: none/long-edge/short-edge
>
> I think the options currently used by the Fujitsu and Avision
> backends (and perhaps others) are sufficient: source = flatbed | ADF
> front | ADF back | ADF duplex.

Hmm, I'm more in favour of limiting source to flatbed and ADF and have
extra options on the ADF source.  Anyone dealing with scanners that
have multiple ADF units?  I have some with "multiple" TPU units.  They
have two areas on the flatbed to scan transparencies.  The user has to
indicate which one should be used.

> [snip]

Hope this helps,
-- 
Olaf Meeuwissen                          EPSON AVASYS Corporation, SE1
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