gamma4scanimage Man page

gamma4scanimage SANE Scanner Access Now Easy gamma4scanimage


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 is 1.0, if the value is
larger than 1.0 then the image gets 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 has to be in the range [0..maxin],
highlight has to be 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 bits gamma input then maxin has
to be set to 255, for 10 bits 1023, for 12 bits 4095, for 14 bits
16383. The default is 16383. To find out what value maxin has to be
call scanimage with a very large gamma table [0]0-[99999]255 then scan‐
image prints an error message with the needed size of the gamma table.

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

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




Oliver Rauch


10 Jul 2008 gamma4scanimage