[sane-devel] Well known option consensus

[m. allan noah]

On 1/21/07, abel deuring <adeuring at gmx.net> wrote:
> Étienne Bersac wrote:
>
> >   \section{Papersize}
> >
> >   When using an Automatic Document Feeder, the user generally cannot
> >   preview. If the page being scanned is smaller than the maximum size
> >   supported by the hardware/backend, the frontend cannot determine
> >   the location of the document on the scan surface, and cannot limit
> >   the values of the scan area (tl-x/y and br-x/y) to match.
> >
> >   If the backend implements options for the frontend user to set the
> >   paper size, the backend should limit the range of the scan area to
> >   that defined by the paper. The scan area is then relative to paper
> >   origin, not scan surface origin.
> >
> >   \begin{options}
> >     \option{paper-width}{\FIXED}{\MM}{Paper width.}
> >     \option{paper-height}{\FIXED}{\MM}{Paper height.}
> >   \end{options}
>
>
> Now things become really tricky ;) Some Fujitsu ADF scanners (and
> probably also devices from other manufacturers) have a so-called
> "overscan mode". In overscan mode, the scan window is larger than
> the page size; for pixels outside tha page area, you get a
> background colour (you can even select between white and black
> background). This allows to detect and correct skewed scans and to
> check the page size by "analyzing" the image.
>
> So, stating that the scan window should not be larger than the page
> size is not such a good idea...
>
> It might be better if the backend tells the frontend, if scan window
> coordinates are relative to the entire scan area or to the selected
> page size.
>

abel- i tried this a few weeks ago with my 4120C2, and found that i also had to
increase the paper size (lie to the scanner) to get it not to throw an error.

can you check in your personal modification that you actually can set
the br-x wider than paper-width? even if this is so, i bet you cannot
set it very much higher. i think i can deal with this in backend- when
overscan is set, i am going to add 16mm to your scan area dimensions
anyway...

allan

> Abel
>
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