---
name: "gamma4scanimage"
section: "1"
platform: "linux"
package: "sane"
version: "1.4.0-4"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gamma4scanimage"
---

# gamma4scanimage(1)

create a gamma table for scanimage

## NAME

gamma4scanimage - create a gamma table for scanimage

## SYNOPSIS

**gamma4scanimage** *gamma* \[*shadow* \[*highlight* \[*maxin* \[*maxout*\]\]\]\]

## DESCRIPTION

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)](/scanimage/1.md) with a very large gamma table \[0\]0-\[99999\]255 and [**scanimage**(1)](/scanimage/1.md) 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.

## EXAMPLE

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

## SEE ALSO

[**sane**(7)](/sane/7.md), [**scanimage**(1)](/scanimage/1.md)

## AUTHOR

Oliver Rauch

## EMAIL-CONTACT

*Oliver.Rauch@Rauch-Domain.DE*