Much of the power of scanimage comes
from the fact that it can control any SANE backend. Thus,
the exact set of command-line options depends on the capabilities
of the selected device. To see the options for a
device named dev, invoke scanimage using:
scanimage --help --device-name dev
The documentation for the device-specific options printed by --help is best explained with a few examples:
The option --brightness expects an option value in the range from -100 to 100 percent. The value in square brackets indicates that the current option value is 0 percent.
The option --default-enhancements has no option value. It should be thought of as having an immediate effect at the point of the command line at which it appears. For example, since this option resets the --brightness option, the option-pair --brightness 50 --default-enhancements would have no effect and the options would be set to defaults.
The option --mode accepts an argument that must be one of the strings ``Lineart'', ``Gray'', or ``Color''. The value in the square bracket indicates that the option is currently set to ``Gray''. For convenience, it is legal to abbreviate the string values as long as they remain unique. It is case-insensitive. For example, option setting --mode col is identical to --mode Color.
The option --custom-gamma expects either a ``no'' option value, or a ``yes'' option value. The value in square-brackets indicates that the option is not currently active. Attempting to set the option would result in an error message. The set of available options typically depends on the settings of other options. For example, the --custom-gamma table might be active only when a grayscale or color scan mode has been requested.
Note that the --help option is processed only after
all other options have been processed. This makes
it possible to see the option settings for a particular
mode by specifying the appropriate mode-options along with the
--help option. For example,
the command line:
scanimage --help --mode color
would print the option settings that are in effect when the color-mode is selected.
The option --gamma-table expects zero or more values in the range 0 to 255. For example, a legal value for this option would be ``3,4,5,6,7,8,9,10,11,12''. Since it is cumbersome to specify long vectors in this form, the same can be expressed by the abbreviated form ``[0]3-[9]12''. This means that the first vector element is set to 0, the 9-th element is set to 12 and the values in between are interpolated linearly. It is possible to specify multiple such linear segments. For example, ``[0]3-[2]3-[6]7,[7]10-[9]6'' is equivalent to ``3,3,3,4,5,6,7,10,8,6''.
The option takes an arbitrary string value (which happens to be a filename). The value in brackets shows that the option is currently set to the filename /tmp/input.ppm.