[sane-devel] newbie

[Ralph Little]

Hi,

On 2021-01-25 6:24 a.m., Matt Zagrabelny via sane-devel wrote:
> Greetings SANE folks,
>
> I'm looking to get into scanning in the GNU/Linux world - I do not yet
> own a scanner. I know the SANE compatibility matrix exists [0], but I
> am hoping for some anecdotal recommendations.
>
> What scanners are people using and how happy are you with your scanner
> and your SANE front-end?

The users of SANE are a pretty mixed bag. The current state of play is
that many new scanning devices are moving to a small number of related
protocols that are not open but are somewhat standard lead by moves by
Apple.
This is good news for Linux scanning although it would be cool if the
standards were fully open.
These protocols are supported by the sane-escl and sane-airscan backends.

Also, we do have a fairly large number of users that are using the
rather excellent and compact LiDE scanners from Canon. These are mainly
supported by the genesys backend (although some are not Genesys based)
which has recently been rewritten and for which there remain some
wrinkles to iron out.

The other massive body of users are for Canon's multifunction PIXMA
devices which are cheap and for the most part support some form of their
BJNP or MFNP protocols, although they are now moving to Apple's
protocols for new machines (at least for network scanning at any rate).
There is a huge number of these devices out there and most are
supported. Some are problematic though due to differences in their
implementations (some return JPEG instead of raw image data for instance).

>
> Also, I read a short blog post [1] about the author's scanner yielding
> different results under Windows and GNU/Linux. The author claims that
> the Windows driver can have better color accuracy. Does anyone have
> any commentary about such notions?
>
There are a number of issues to bear in mind:

1. Many scanners are supported due to reverse engineering since their
protocols are secret, and each implementation of that protocol may have
subtle variations in the target hardware. This is a time-consuming and
often imprecise (and incomplete) process.

2. Often a lot of supported features are actually in the driver or
supplied support software and not a feature of the device itself. The
SANE project is largely involved in supporting the hardware. These
additional features are therefore not revealed by the hardware support
provided by SANE, although some backend authors try to extend that by
implementing some features in the backend. It is a mixed bag. Some of
this may be related to the problems in the referenced article. I'm not sure.

3. Support for some scanners are through their untested familial
relationship to scanners that HAVE been tested. I have discovered a
number of scanners that purport to be supported but were clearly not
tested to any great degree in practice. So we sometimes have queries
about "supported" scanners that are clearly not supported at all.

4. As an extension to 3. above, we do find that some scanners that were
supported are broken due to past refactoring work. It is a recurring
problem that SANE authors don't often have access to the full gamut of
supported hardware to perform regression testing. Of note, we have a
recurring JPEG issue in the xerox_mfp backend, Genesys devices supported
by the genesys backend, and recently an issue in the avision backend
which is now fixed.

5. Some manufacturers DO support Linux (notably HP although not their
earlier flatbed scanners and fairly completely and their drivers are
open source.) They are not supported by the SANE project but the third
party drivers use the SANE API.

> Thanks for helping me get my feet wet.

There is always a need for contributors for doc, reverse engineering,
maintenance etc.
You should pick a topic that interests you and for which you believe you
have sufficient skill.

In order to get into the coding side, I would certainly suggest getting
something cheap (or free if Thrift stores/Craigslist/Gumtree etc are
available to you). You would be surprised what you can pick up for next
to nothing if you are patient.

If you have specific questions as to how to get up to speed, you can ask
them here and someone will chime in.
>
> Cheers,
>
> -m
>
> [0] http://www.sane-project.org/sane-supported-devices.html
> [1] https://www.digitaltidying.com/dont-use-linux-to-scan-photographs/