[sane-devel] How to adjust colours?

[Rodolfo Medina]

On Sonntag, 1. Juli 2007, Rodolfo Medina wrote:

>> I'm scanning a colour photo and want to diminish the red, but the
>> --red-gamma-table option is inactive.  What to do?
>> 
>> I have Debian Etch and a Canon CanoScan LIDE 25.



Gerhard Jaeger <gerhard at gjaeger.de> writes:

> Try
> scanimage --custom-gamma=yes --help   
>
> and --red-gamma-table should be active



I did as you suggest, then I did:

 $ scanimage --mode Color --custom-gamma=yes --red-gamma-table 50 -x 210 -y 290 > photo.pnm

, and the --red-gamma-table option was active now.  But, maybe because I don't
know how to use it, I can't get what I want: any value for --red-gamma-table
only turns grey into red and red into grey, more and more from 0 to 255.  I
also tried with the --gamma-table option, but that remains inactive:

 $ scanimage --mode Color --custom-gamma=yes --gamma-table 100 -x 210 -y 290 > photo.pnm
scanimage: attempted to set inactive option gamma-table

. Please, any help?
Thanks,
Rodolfo