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

[Olaf Meeuwissen]

2cv67 <2cv67 at free.fr> writes:

> Hi! I am new here & out of my depth, so please excuse dumbness...
>
> I am using an Epson Perfection V200 scanner in Lubuntu 11.10 & also in
> Ubuntu 10.04.
>
> Using Epson's Avasys iScan (2.28.1-3ltdl7 etc) then I get offered a
> huge range of dpi's, all of which seem to work as far as I checked.
> 50/72/96/150/200/240/300/360/400/600/720/800/1200/1600/2400/3200/4800/6400/9600dpi...

These resolutions are courtesy of iscan and almost completely unrelated
to the resolutions that the device is capable of.

> I mainly use this application, but it has some practical &
> philosophical negatives so I would like to be able to use a 'proper'
> Linux app if possible.

Care to explain about those negatives?

> When I try to use XSane, then I get offered different X & Y dpi's
> which mostly don't match: X=75/300/600/1200/2400/4800
> Y=100/200/300/400/600/800/1200/1800/2400/3600/4800/6600/9600

These are the resolutions the device is capable of and you should be
able to scan at any combination.  So 300dpi in the X direction and 400
dpi in the Y direction.

> This means I really only have 300/600/1200/2400/4800 as usable values.

Only if you insist on using the same resolution in *both* directions.
If you use different resolutions for the X and Y directions, you really
should make sure they are incorporated in the image's metadata.  If you
don't, chances are you get weirdly elongated images in one direction.

> I don't need a vast range of dpi's, but for everyday use I really want
> a couple of values below 300, preferably 150 & 100.

With iscan you have 150 and 96, but internally it will use 300dpi, IIRC,
and then scale the image down to the selected resolution.

> I also tried Simple Scan, which seemed like the perfect answer for the
> rest of the family, but again have a major dpi problem.  Simple Scan
> offers me a good-looking selection of 75/150/300/600/1200/2400dpi.

These are courtesy of Simple Scan and completely unrelated to what the
device is capable of.

> But 75/150/300/600/1200 all result in scanning at 300dpi & trying 2400
> results in a memory error.

The memory error at 2400dpi is probably an issue with Simple Scan, as
iscan has been tested to work fine at even higher resolutions (but you
can not scan the whole flatbed area).

> I raised a bug for Simple Scan & Michael Nagel there is being very
> helpful but it looks like the root cause is probably the odd selection
> of dpi's coming out of Sane.
> https://bugs.launchpad.net/simple-scan/+bug/891586

Hmm, looks like Simple Scan just doesn't scale the acquired image to the
resolutions that it advertises.  It certainly should not assume that all
scanners are able to scan at those resolutions, nor that resolutions in
the X and Y directions are always the same.

> My Ubuntu Forum thread from 2010 with more details:
> http://ubuntuforums.org/showthread.php?t=1577867
>
> So - my questions are:
> 1. Is that weird set of X & Y dpi's what I should be seeing for this
> scanner?

Yes.

> 2. Can I do anything to get other values - preferably with same X & Y,
> particularly 75/100/150 ?

You're best bet is probably post-processing of the image with something
like `convert` for command-line based work (part of the imagemagick and
graphicsmagick packages) for example, or the GIMP if you prefer a GUI.

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