.TH gamma4scanimage 1 "10 Jul 2008" "" "SANE Scanner Access Now Easy"
.IX gamma4scanimage
.SH NAME
gamma4scanimage \- create a gamma table for scanimage
.SH SYNOPSIS
.B gamma4scanimage
.I gamma
.RI [ shadow
.RI [ highlight
.RI [ maxin
.RI [ maxout ]]]]

.SH DESCRIPTION
The tool
.B gamma4scanimage
creates a gamma table in the format expected by scanimage. You can define a
.BR gamma,
a
.BR shadow
and a
.BR highlight
value. You also can specify the size
.RB ( maxin )
and maximum output value
.RB ( maxout )
of the gamma table.
.PP
.BR gamma
is a floating point value, neutral value being 1.0. If the value is larger than
1.0 then the image is brighter.
.PP
.BR shadow
defines the minimum input value that is necessary to create an output value
larger than zero.  shadow has to be in the range
.RB "[0.." "maxin" "]."
Its default value is 0.
.PP
.BR highlight
defines the maximum input value that produces an output value smaller than
maxout.  highlight must be in the range
.RB "[0.." "maxin" "]"
and
larger than shadow. Its default value is the same as
.B maxin
(16383 if not set).
.PP
.B maxin
defines the size of the gamma table. The size depends on the scanner/backend.
If the scanner uses 8 bit gamma input then
.B 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
.B maxin
has to be, call
.BR scanimage (1)
with a very large gamma table
[0]0-[99999]255 and
.BR scanimage (1)
will print an error message with the needed gamma table size.
.PP
.B maxout
defines the maximum output value. Take a look at the output of
.I scanimage \-h
to find out what
.B maxout
must be. The default value is 255.
.PP
.SH EXAMPLE
scanimage \-\-custom\-gamma=yes \-\-gamma\-table
`gamma4scanimage 1.8 0 11500 16383 255`
>image.pnm

.SH SEE ALSO
.BR sane (7),
.BR scanimage (1)

.SH AUTHOR
Oliver Rauch

.SH EMAIL-CONTACT
.I Oliver.Rauch@Rauch-Domain.DE