[sane-devel] Can I change resolution offerings for Epson V200 Photo scanner?

[Olaf Meeuwissen]

Michael Nagel <ubuntu at nailor.devzero.de> writes:

> Here a copy of my message that I also posted to https://bugs.launchpad.net/simple-scan/+bug/891586
>
> ********************************
>
> The 3 minute freeze: http://lists.alioth.debian.org/pipermail/sane-devel/2012-February/029481.html
>
> The thing is that SANE provides two ways to set the resolution:
>
> A: "resolution" set to some value
> B: "x-resolution" and "y-resolution" are set to some value
>
> Simple Scan supports only method A.
> xsane and scanimage support A and B.
>
> Ususally this is not a problem, but the values for A are very limited
> with your scanner, see the next list.

That is to be expected as it is the intersection of the x-resolution and
y-resolution lists.

> [snip]
>
> Additionally, the list of resolutions displayed in Simple Scan is not
> the list of resolutions supported by the hardware. The list is static,
> and you can select whatever you want. When scanning the next available
> resolution is chosen. In your case the choice is limited to
> 300/2400/4800 as Simple Scan only supports only method A.
>
>>From my point of view there are two things to do:
> 1) Simple Scan should support method B.

Indeed it should.  As a matter of fact, the SANE API doesn't even
guarantee that you can use method A :-)  See section 4.5.2 of the
specification for details.

> 2) Someone with knowledge of the backend/driver should check if these
> lists are correct, especially if the list for method A is really that
> short.

That list is correct.

As a third and complementary approach, Simple Scan can scale the image
to the resolution that the user selected.  Image Scan! for Linux does
that.  Right now, Simple Scan gives the user the false impression that a
certain resolution is used to get and create an image.  All it really
does is let the user select a lower bound on the resolution.  And it
does that without clearly saying so.  The user will expect an image with
the UI selected resolution (no matter what was used to get it).  If the
selected resolution is wildly different (and smaller) than that used to
acquire the image, users may get impatient because it takes such a long
time but that's another issue.

Hope this helps,
-- 
Olaf Meeuwissen, LPIC-2           FLOSS Engineer -- AVASYS CORPORATION
FSF Associate Member #1962               Help support software freedom
                 http://www.fsf.org/jf?referrer=1962