Frederik Ramm wrote:
> What's more, my scanner supports a few settings with funny names I
> cannot make sense of. Maybe somebody knows what they are, or what they
> might be. It would be interesting for me if it is worthwile to make
> them available through the backend.
>
> * Initial Slice: Specifies the initial binary threshold value when in
> floating slice mode.
> * Up value: Specifies the +UP count value used in floating slice mode.
> (Valid settings: 0-3, default: 1)
> * Down value: ... as above
> * Lower Limit Slice: Specifies the lower limit slice used in floating
> slice mode (0-15, default: 6)
Hmmm.. "floating slice"... This sounds familiar... Our big Fujitsu
document scanner has (two) "dynamic threshold" modes. Perhaps the FS
mode is something like DT.
DT is a line art mode, where the scanner automatically adapts the
threshold between "white" and "black" parts. This is particularly
useful, when You have a gradient color in the background. The DT mode
however made use of several parameters, and the tuning of these
parameters is an art of it's own.
There was a "simplified DT" mode with a straighter parameter set.
Enhancement mode was a kind of spacial high pass filtering. Thus, edges
are amplified.
The main reason for implementing this - and some very nifty nonlinear
filters for OCR - within the scanner is speed: You get a perfectly
preprocessed G4-compressed line art from the scanner within a second or
two, and it needs no CPU on Your machine.
After all, if scanning speed and CPU cycles are irrelevant, there is
absolutely nothing, that You cannot do within the driver. Most
manufacturers seem to size the scanner API down with this "vision" in
mind...
Hope it helps...
-- Marian Eichholz
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