Man1 - gamma4scanimage.1

gamma4scanimage - create a gamma table for scanimage

gamma4scanimage gamma [/shadow/ [/highlight/ [/maxin/ [/maxout/]]]]

The tool gamma4scanimage creates a gamma table in the format expected by scanimage. You can define a gamma, a shadow and a highlight value. You also can specify the size (maxin) and maximum output value (maxout) of the gamma table.

gamma is a floating point value, neutral value being 1.0. If the value is larger than 1.0 then the image is brighter.

shadow defines the minimum input value that is necessary to create an output value larger than zero. shadow has to be in the range [0..*maxin*]. Its default value is 0.

highlight defines the maximum input value that produces an output value smaller than maxout. highlight must be in the range [0..*maxin*] and larger than shadow. Its default value is the same as maxin (16383 if not set).

maxin defines the size of the gamma table. The size depends on the scanner/backend. If the scanner uses 8 bit gamma input then maxin must be set to 255, 1023 for 10 bits, 4095 for 12 bits, and 16383 for 14 bits. The default is 16383. To find out what value maxin has to be, call *scanimage*(1) with a very large gamma table [0]0-[99999]255 and *scanimage*(1) will print an error message with the needed gamma table size.

maxout defines the maximum output value. Take a look at the output of scanimage -h to find out what maxout must be. The default value is 255.

scanimage –custom-gamma=yes –gamma-table `gamma4scanimage 1.8 0 11500 16383 255` >image.pnm

*sane*(7), *scanimage*(1)

Oliver Rauch

Oliver.Rauch@Rauch-Domain.DE