[sane-devel] Pixma lamp control

[Ralph Little]

Hi,


On Sat, Nov 1, 2025, 03:04 <jp at byjp.me> wrote:

> Hello,
>
> I'm interested in driving SANE to scan twice in succession (one with the
> lamp on, one with the lamp off), so I can scan against a lightbox (with
> *its* lamp off, and on, respectively) to manufacture an alpha layer for
> my scanned image.
>
> (I’m scanning postcards; some have unusually shaped edges, and with
> examples of every colour touching the edge of the card — my attempts at
> automating masking with alpha mattes work only some of the time)
>
> I have a Pixma scanner (CanoScan LiDE 400), for which SANE doesn't declare
> any lamp-related options (with scanimage -A). I’m a software & firmware
> engineer, so I’m comfortable getting into the detail, but I wanted to learn
> from the community first:
>

The Lide 400 uses the pixma backend which uses a high level protocol to
request scans. If you intend to manipulate the scan lamp then you would
need to access the hardware directly in which case you would probably not
be using SANE. There is a huge variety of ways in which scanners are
controlled. The multifunction devices by Canon, Xerox, HP, etc all use very
higher level protocols and hardware is handled internally by the device's
firmware so there isn't usually any provision for you to manipulate the
device at a low level. To go that route you need to go for a device that is
controlled more finely such as the Genesys scanner-on-a-chip models. See
the Genesys backend to see what models are currently supported. Other
backends also support devices that are controlled at the lower level where
lamp control may be possible.

Cheers,
Ralph
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