> Question 1 - How to do duplex scanning.
>
> If SANE doesn't support that, I could introduce a new parameter that
> controls whether the front or rear side is to be scanned, and each
> page would have to be run through the scanner twice. A waste, but
> possible.
> I've grepped for "duplex" in the existing backends (1.0.4) but found
> nothing.
None of the backends in 1.0.4 can do duplex scanning AFAICT
Handling duplex in the front-ends is probably a bit much, certainly
not something that can supported through the SANE 1.0 standard without
incompatible tweaks.
You might consider buffering the alternate side in SANE driver, which
will typically be on a decent-sized PC or server. A whole page is a
lot of data to buffer, especially in color, but these days that might
be a lot more practical than re-scanning everything.
When scanning the first page, half the data goes in this large buffer,
then when the frontend asks for another page it comes out of the
buffer very quickly. The buffer can be discarded when the frontend
calls ..._close() so it won't take up RAM all the time.
Of course you still need a "duplex?" setting, because users don't want
to scan both sides of a single-sided document :)
> Question 2 - How to do the color thing.
>
> incomplete data at the beginning and the end of the data stream. If I
> request an image of, say, 100 pixels in height, will the scanner then
> give me 100 of which only 84 are fully usable, or will it give me 116?
This sounds like something very specific to your scanner. I hope you can
figure out how to get the right results to the frontend.
Nick.
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This archive was generated by hypermail 2b29 : Tue Feb 27 2001 - 09:25:32 PST