SANE-umax backend

This backend dynamically enabeles the options that are supported by the scanner in dependence of the scanning-mode and other options. Here is an example of the frontend XSane:


The options Gamma, brightness, contrast and negative in the main window come from xsane that calculates a gamma table using this values. These values are corelated to highlight, midlight and shadow sliders in the Histogram window.

Scan modes:

Mode Remark
Lineart 1 bit/pixel black/white mode
Halftone 1 bit/pixel dithered black/white mode
Grayscale 8 / 9 / 10 / 12 / 14 / 16 bits/pixel gray mode
Color 24 / 27 / 30 / 36 / 42 / 48 bits/pixel RGB mode

Scan sources:

Scan sources
Transparency adapter (UTA)
Automatic document feeder (ADF)

Standard options:


Standard options Remark
Analog gamma correction Define the value for analog gamma correction. *
Value between 1.0 and 2.0 .
(Analog gamma correction doesn't reduce the number of used colors)
Highlight Define the intensity that shall be considered white. *
Shadow Define the intensity that shall be considered black. *
Contrast Define the contrast of the image - only available in halftone-mode.
Brightness Define the brightness of the image - only available in halftone-mode.
Threshold Define the minimum intensity to get a white point- only available in lineart-mode.
Use custom gamma table Use free definable scanner internal digital gamma table.
If you enable this option, the gamma correction is done inside the scanner. If you have a scanner with more than 8/24 bits/pixel, the image is scanned with the maximum available bit depth. The gamma correction does transform the image form the internal bit depth to the selected output bit depth (see below).
The frontends do handle the usage of the gamma table different. If you use xsane, you should enable this option to use the maximum available bit depth (otherwise xsane does the conversion with the selected output bit depth).
(Side-effect: digital gamma correction may reduce the number of used colors -especally if the used bit depth is low.)
Quality calibration Use quality white calibration. *
Double optical resolution Use lens 2 on high end scanners, this reduces the scanwidth and increases the maximum scanresolution. *
Negative scan Inverts color intensity - for scanning negatives.
Bit depth Image depth in bits/sample the scanner sends to the computer, normally 8 in grayscale and color mode. Some scanners support more than 8bits/sample, but only few file formats support it. If your scanner supports more than 8bis/sample you already get an improvement if you set the bit detpth to 8 and enable the option use custom gamma table (see above) because the scanner internal gamma correction is done with the maximum available bit depth!!!
*** There is normally no reason to use more than 8 bits/sample! ***
Lamp warmup Enable extended lamp-warmup. *

* only available for some scanners

Author: Oliver Rauch