[sane-devel] plustek backend - "lamp-switch" option

Alexander Hofmann alexander.hofmann at new-h.de
Thu Apr 18 20:32:51 UTC 2013


Am 16.04.2013 08:24, schrieb Gerhard Jäger:
> Hi,
> On Sunday 14 April 2013 16:03:49 Alexander Hofmann wrote:
> [...]
>> Does that mean that the scanner supports scanning with the lamps off?
>> (e.g. to scan negatives)?
> no. Switching the lamps while scanning is performed by the backend.
Indeed, I located the code (calls to usb_LampOn in plustek-usb.c)...

>> If so, how should I use that option?
> This option is available to provide a way for a possible frontend
> like XSane for switching on or off the lamp manually for example
> before doing a scan. Could be interesting when skipping the warmup
> option - which is in fact only useful for CCD based scanner that
> hav a CCFL lamp.
Ok, so not what I was searching for. Switching lamps off and on during
scans/calibration steps when using CCFL tubes might not be the best idea

> Regarding writing a backend, this one could be a starting point
> http://www.sane-project.org/backend-writing.txt
That one helped me out: I was able to add a new option, "dark-scan" to
the plustek backend, that causes the driver to switch of the lampes the
moment the scan begins. It works like a charm - digitizing old S/W
negatives works, and so does scanning pictures projected by "scanner
cameras". As the scanner is recording red, green and blue channels one
by one, color's not possible of course, except with using filters and
scanning the image thrice, witch might produce some interesting results
when using IR, I've yet to check that.

If there's interest in the change, I could try to provide a patch,
although I'm not very familiar of using git...

Thanks for the help,


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