[sane-devel] How to read from a sensor including its margins?

[Ralph Little]

Hi Paul,

On Wed, May 19, 2021 at 8:40 AM Paul Wolneykien <manowar at altlinux.org>
wrote:

>
>   Hi, SANE developers!
>
>   I want to know is it technically possible to read all available
> sampling data from a CIS sensor, including its the margins --- i.e.
> the areas that are normally covered by the left and right bars of
> the scanner's front frame?
>
>   Look at the picture, please: https://ecloud.global/s/H9JE8mXftwS8znK.
> As we can see, the CIS sensor seems to be wider than the lamp, does it?
> May be I'm just isn't right about that...
>
>   As my Canon LiDE 220 scanner is driven by the "genesys" backend
> I've tried to set SANE_DEBUG_GENESYS_IMAGE=1 env var, and found that
> the resulting low-level images do not contain any extra pixels. Does
> anybody know is it possible to get data for that extra-width areas?
>
>     TIA,
>       Paul.
>
> Polivas would be the best person to answer this question, but I believe
that some of the genesys controllers have registers that specify the left
and right extents of the sensor to include in data. You might be able to
modify the genesys backend to inject updates to those registers to extend
the extents somewhat.  It would be a little bit more involved than that
though because the backend also limits the data sent back based on the
perceived width of the device so you would have to fiddle with the defined
specifications of the device.

I don't seem to have a datasheet on the GL124 device that is supposedly in
it so I cannot help you with that. It might not be available. I know that
not all of them are.

Cheers,
Ralph
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