[sane-devel] duplexing question

[m. allan noah]

Jazz said:

> This requires the front end to make two calls to sane_start for each duplex page scanned.
> In Xsane, the user must click on "SCAN" button twice, or set the "Number of Pages to Scan"
> counter to 2. Then the first time the user clicks the SCAN button, the scanner will feed one
> page through the ADF and scan both sides at that time. The frontend will then read the
> first side's data and save that as out.0001.pnm and then on the second sane_start it
> will simply continue reading image data for side 2 from the scanner's memory,
> and then save that as out.0002.pnm.
>
> Seems slightly awkward, unless there's a way to have the OPT_DUPLEX option somehow
> automatically set the "Number of Pages to Scan" counter. Have I misunderstood something,
> or is this how the other backends duplex with Xsane?

yeap- thats how it works. there is no way for the hardware to tell how
many sheets are inside, so there is not much point in a method for the
backend to tell the frontend that more pages are coming. its up to the
user who selects 'duplex' to understand that he's gonna get multiple
images.

I'm willing to bet that most folks with higher end duplex hardware are
not using xsane to drive the machine, other tools like scanimage and
scanadf are more tuned for that job.

allan

>
> Thanks.
>
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