[sane-devel] pixma backend: -x/y auto advertised but not available / how to crop?

[m. allan noah]

That 'auto' string is put there by scanimage, when it finds an option
with the SANE_CAP_AUTOMATIC capability set. Unfortunately, scanimage
has some special handling for the x/y/t/l parameters. It appears that
-l and -t will properly parse the 'auto' string, but -x and -y will
not. This is a bug in scanimage, specifically in parse_vector().

If the pixma devices are unable to detect paper width in hardware, the
SANE_CAP_AUTOMATIC cap should be removed from those options. Or, the
pixma backend could be extended to use sanei_magic library, which
other backends use to add features like deskew and crop.

Outside of modifying sane-backends, you might look at the program
unpaper for post-processing the images.

allan

On Thu, Apr 27, 2017 at 5:05 PM, Manuel Reiter <manuel at reiter.pm> wrote:
> Nobody? I found this old discussion which seems to suggest the pixma devices don't support auto-detection:
>
> http://lists.alioth.debian.org/pipermail/sane-devel/2009-December/025674.html
>
> If that's indeed the case, may I suggest updating the pixma backend so that it doesn't advertise capabilities that don't exist?
>
> Also, I'd still appreciate suggestion for a scriptable approach to achieve this functionality.
>
> Thanks,
>
>   Manuel
>
> Am 11.04.2017 um 16:44 schrieb Manuel Reiter:
>
>> I'm using saned with a Pixma MP610 all-in-one on a Raspberry Pi 3 running an up-to-date Rasbian Jessie. scanimage --help shows me the following options for Geometry:
>>
>> [...]
>> Options specific to device `net:localhost:pixma:04A91725_414EE7':
>> [...]
>>  Geometry:
>>    -l auto|0..216.069mm [0]
>>        Top-left x position of scan area.
>>    -t auto|0..297.011mm [0]
>>        Top-left y position of scan area.
>>    -x auto|0..216.069mm [216.069]
>>        Width of scan-area.
>>    -y auto|0..297.011mm [297.011]
>>        Height of scan-area.
>> [...]
>>
>> However, trying to actually use "-x auto" results in an error:
>>
>> ------snip
>> reiter at hive:~ $ scanimage -d net:localhost:pixma --mode Color \
>> --resolution 300 -l auto -t auto -x auto -y auto > /dev/null
>> scanimage: option --x: bad option value (rest of option: auto)
>> ------snip
>>
>> Is this a bug or an error on my part?
>>
>> I intend to use this scanner for a document management system and expect to scan quite a number of non-full-size documents. If x/y auto is indeed not available, what would be a good way to automatically crop my scans? The included (Mac) Software actually does a decent job so it seems to be possible.
>>
>> Thanks in advance for your answers!
>>
>> Cheers,
>>
>>  Manuel
>>
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