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"
