[sane-devel] --gamma-table: totally baffled

Ferenc ferenc@avz.xs4all.nl
Sun, 9 Sep 2001 23:23:17 +0200


First, thank you all for coding this great piece of software. It allows 
me to build a web-interface to my Mustek 12000SP scanner.

This brings me to my problem: dark scans. It would seem a gamma-
correction of about 2 would solve this. I wish to do this in the 
scanimage commandline options, i.e. the option --gamma-table. This 
seems to be the only option to solve this problem, as brightness only 
pertains to lineart scans. I do color scans.

You see, this option utterly and completely baffles me. I have no 
idea whatsoever about the numbers I should put there. Of course 
I've searched mostang.com and googled for an explanation. I've 
read Poynton's excellent Gamma-faq but even that does not begin to 
give a hint. At one time, I copied the complete mostang mailing-list 
archive to my harddisk and let grep sweat it out, but I seem to be the 
only one not understanding (or using) --gamma-table.

From the sane-sharp manpage I gather one should enter 255 
Status: O

values. Do these numbers describe a curve or something? Do 
people seriously enter 255 values after --gamma-table?!

Please enlighten me!