[sane-devel] Reflecta ProScan 7200

[m. allan noah]

On Wed, Apr 27, 2011 at 4:00 PM, Michael Rickmann <mrickma at gwdg.de> wrote:
> Am 26.04.2011 23:41, schrieb m. allan noah:
>>
>> On Tue, Apr 26, 2011 at 5:17 PM, Michael Rickmann<mrickma at gwdg.de>  wrote:
>>>
>>> Hi Jan,
>>>
>>> Am 24.04.2011 00:58, schrieb Vleeshouwers, J.M.:
>>>>
>>>> Hi Michael,
>>>>
>>>> A short update on a couple of settings (mode normal/quality,
>>>> auto-exposure, auto-gamma, and ICE).
>>>> For details see:
>>>> http://www.stadspartijeindhoven.nl/jv/SettingsAnalysis.ods I'm not
>>>> completely ready with all settings yet, but If you
>>>> have suggestions for additional tests, let me know.
>>>
>>> Thanks a lot, I am constantly looking up things in your tables instead of
>>> doing test scans under Windows. I have been busy teaching the pie backend
>>> 16-bit colours and larger read sizes than a single line. That kept me
>>> busy,
>>> so I have not done much progress with regard to the interpretation of
>>> snoops. But from the practical point of view, I wonder whether GAMMA can
>>> be
>>> sent to the scanner or has to be handled by software - my native scans
>>> are
>>> far to dark - it nags - and a preset GAMMA of 2.2 as Windows-Silverfast
>>> uses
>>> would be just ideal. So far I have seen no indication that the Win progs
>>> send any related information over USB. And GAMMA as sent by the pie
>>> backend
>>> is not accepted by my scanner: IO-error.
>>
>> extract the image data from a windows snoop, and see if it is dark too.
>>
>> allan
>
> Thank you, allan! The snooped image from Windows-Cyberview looks nearly
> identical to the Xsane one with software gamma set to 1.0 (all OPT_GAMMAs
> set to SANE_CAP_INACTIVE in the backend), have a look at 300q-snoop-cy.pnm
> and 300q-g10-xs.pnm at
> http://wwwuser.gwdg.de/~mrickma/sane-proscan-7200/status-270411/ . When
> looking at 300q-22g-xs.pnm (sofware gamma set to 2.2 in Xsane) it pretty
> well fits the Windows-Cyberview one in 300q-cy.jpg.
> My question is now, whether there is an option for SANE backends to tell the
> frontend that it is unable to do gamma by hardware but would like to use a
> preset gamma as standard. Are there any other backends which do/need that?
> Regards
> Michael

Many scanners cannot do gamma or even brightness/contrast in hardware.
This gives you two choices:

1. disable the gamma option, the frontend won't attempt to call it.
2. simulate the gamma inside the backend, using a lookup table or some such.

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