[sane-devel] Scan Correction Program! :)

[m. allan noah]

sniffer: http://www.pcausa.com/Utilities/UsbSnoop/default.htm

see also http://www.sane-project.org/contrib.html and
pirsoft-dsl-dropzone.de/scanner-technical.pdf for more info

allan

On Mon, May 12, 2008 at 8:14 AM, Ekkehard Morgenstern
<ekkehard at ekkehardmorgenstern.de> wrote:
>
>  Thank you! :)
>
>  How do I log USB communication in Windows?
>
>  I might try to implement what you said sometime. I love controlling
>  devices! :)
>
>  I also have to analyze the source code of the backend. Its implementor
>  already used reverse engineering data, perhaps code that I'd need is
>  already there.
>
>  I've never done driver development on Windows, Linux or BSDs, but I'm
>  certainly interested in it! :)
>
>  And since SANE operates on top of normal OS services, this would be like
>  an initiation rite for me! ;)
>
>
>
>  On Mon, 2008-05-12 at 07:51 -0400, m. allan noah wrote:
>  > The results might be caused by poor (or no) CIS calibration being done
>  > by the backend. You could try getting a trace of the device in action
>  > with the windows driver, and investigate adding the calibration steps
>  > to the backend.
>  >
>  > generally this involves doing several small scans of a white area
>  > under the shell of the scanner, with and without the lamp on. this is
>  > usually pretty easy to identify in the logs. interpreting it is a
>  > different matter... :)
>  >
>  > allan
>  >
>  > On 5/12/08, Ekkehard Morgenstern <ekkehard at ekkehardmorgenstern.de> wrote:
>  > >
>  > >  It's the ma1509 backend.
>  > >
>  > >  I've already seen that there's a possibility to provide gamma correction
>  > >  tables and such to SANE from within a backend. How does it work?
>  > >
>  > >  I'm not sure whether the poor results of my scanner are the result of
>  > >  hardware aging, or if it's just because the backend seems to pass on the
>  > >  data from the scanner chipset unchanged.
>  > >
>  > >  It's an LED scanner, so there must be a set of photo diodes or photo
>  > >  transistors somewhere. It appears as if the scanner sends the data in
>  > >  raw form, unadapted to the characteristics of the semiconductors.
>  > >
>  > >  Distribution of RGB values across their channels suggest that the data
>  > >  should be scaled or transformed somehow. I spent a whole night this
>  > >  weekend trying to figure out some formula that would solve the problem,
>  > >  but I didn't find a solution.
>  > >
>  > >  Instead, I wrote this program to simply compute the difference between a
>  > >  blank page and the color white. The program generates one line of
>  > >  averaged out scaling data, which is stored in the file "white.shape".
>  > >  I'm not sure whether the data can be made constant. If it were to be
>  > >  included in the backend driver, it has to be fairly constant over all
>  > >  scanners of that type.
>  > >
>  > >  After all, the Windows driver must do the same thing somehow! ;)
>  > >
>  > >
>  > >
>  > >  On Sun, 2008-05-11 at 15:42 -0400, m. allan noah wrote:
>  > >
>  > >  > Ekkehard- another choice might be to do this sort of calibration
>  > >  > inside the driver in sane, but that would require becoming familiar
>  > >  > with the code of the sane backend which drives the scanner....
>  > >  >
>  > >
>  > >
>  > >
>  >
>  >
>
>



-- 
"The truth is an offense, but not a sin"