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Hi,<br>
There are other backends that support transparency but the genesys
chips are pretty much a world of their own. On the upside, the GL646
is pretty well documented.<br>
I believe the main ways in which the transparency support would be
invoked would be via the source and options related to capture type.
I don't see any specific image capture type-related options in the
backend but some would have to be added I suspect (e.g. for
selecting between positive and negative, IR etc).<br>
<br>
The main challenge with genesys-based devices is that every model is
different to every other in implementation. The Genesys chips are
very flexible and offer all sorts of driving options and they need
to be set up for the particular hardware that they are matched with.
The main way to tackle this task is to observe Windows driver
behaviour through capturing traffic and looking at the register
values that are set. It's a little more involved but that is the
main gist.<br>
<br>
I have had some dealings myself with looking at a GL646 device
before although it was a fairly superficial look at motor stepping
tables but I may be able to look at it in the future sometime.<br>
One thing you *can* do (if you have the inclination) is to make some
USB captures on Windows and post them to an issue at our GitLab
issue tracker
(<a class="moz-txt-link-freetext" href="https://gitlab.com/sane-project/backends/-/work_items">https://gitlab.com/sane-project/backends/-/work_items</a>), if you
don't intend to do the implementation yourself. That way someone
could pick up the issue at some point. Ideally a developer needs the
hardware at hand, but a rough stab could be made by looking at the
traffic.<br>
<br>
Cheers,<br>
Ralph<br>
<br>
<div class="moz-cite-prefix">On 2026-07-31 10:01,
<a class="moz-txt-link-abbreviated" href="mailto:7xsuazlhhtls@gmail.com">7xsuazlhhtls@gmail.com</a> wrote:<br>
</div>
<blockquote type="cite"
cite="mid:2d3d1219-1365-4b09-a4ea-feeb08e72f10@gmail.com">
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<p>Ralph,</p>
<p>Thanks for the reply.<br>
<br>
I looked at the Genesys Datasheet for the chip (GL646USB) that
is used in the HP4850. I see the register that appears to
control the slide scanning lamp.</p>
<p>Is there another backend that has support for a similar
feature? Possibly I could use that as a template to better
understand how support for this feature might be implemented in
the genesys backend.</p>
<p>Thanks again,</p>
<p>Jon</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 7/31/26 11:21 AM, Ralph Little
wrote:<br>
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<blockquote type="cite"
cite="mid:7c8c105f-1b7d-4461-8a20-e6cb83788192@gmail.com">
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Hi,<br>
According to our Supported Scanners list (<a
class="moz-txt-link-freetext"
href="http://www.sane-project.org/sane-supported-devices.html"
moz-do-not-send="true">http://www.sane-project.org/sane-supported-devices.html</a>)
the genesys backend doesn't yet support the slide scanning
feature of this device. It requires additional code to drive the
extra hardware involved.<br>
We don't have an active maintainer for the genesys backend at
the moment unfortunately, so I don't know when someone would be
able to get to this task in the future. :(<br>
<br>
Regards,<br>
Ralph<br>
<br>
<div class="moz-cite-prefix">On 2026-07-30 20:58, <a
class="moz-txt-link-abbreviated moz-txt-link-freetext"
href="mailto:7xsuazlhhtls@gmail.com" moz-do-not-send="true">7xsuazlhhtls@gmail.com</a>
wrote:<br>
</div>
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cite="mid:d0f9e851-d9f4-44fd-b3c2-eb6699345df3@gmail.com">
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<p><code>I recently acquired an HP Scanjet 4850 scanner. The
document scanning works with no problems. This particular
scanner has a negative/slide scanning component built in
to the lid of the device. This includes a separate lamp
to illuminate the film for scanning. The lamp in the lid
comes when I run a hardware self test procedure but I have
not discovered any way to have the lamp come on when
scanning using sane.<br>
<br>
Is this capability supported?<br>
<br>
info about my setup ---<br>
<br>
HP Scanjet 4850<br>
<br>
$ scanimage -V<br>
scanimage (sane-backends) 1.4.0; backend version 1.4.0<br>
<br>
genesys backend<br>
<br>
Fedora Linux 44 (Workstation Edition)<br>
Linux 7.1.5-200.fc44.x86_64</code></p>
</blockquote>
<br>
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