[sane-devel] unpaper default parameters

Peter Fales psfales@fales-lorenz.net
Fri, 11 Mar 2005 10:01:37 -0600

The images I'm working with are faxes, so they are typically 1680x2200
pbm (1 bit per pixel) image files.

I wasn't specifying --layout, but adding "--layout single" didn't seem to
help.   Since my pixels are all black or white, I don't think changing
the thresholds would be expcted to make much difference.

Peter Fales
Peter "at" fales-lorenz.net

On Fri, Mar 11, 2005 at 04:07:17PM +0100, Jens Gulden wrote:
> Hello,
> Peter Fales wrote:
> >I get white pages as output on my i686 machine unless I use 
> >--no-border-scan.   I haven't analyzed why - and I'm not sure whether
> >running unpaper with all default arguments is even expected to work.
> You're right, the default parameters are NOT expected to always work
> out-of-the-box. It depends on the input image whether they make sence or
> not. All of my own tests have been made on grayscale paper scans with
> "good" contrast, directly originating from scanadf, size 1648 x 2337 pixels.
> Could it be that your scans are too bright, so that the automatic
> border-scan treats all pixels as non-black pixels? What happens if you
> use different values for --black-threshold or --white-threshold? What if
> you set a --border-scan-threshold even lower than the default of 5?
> Are you specifying the --layout parameter, setting it either to 'single'
> or 'double'? (Most of the automatic processing makes sence with a
> specified --layout only.)
> Please anybody let me know which default values would make more sence
> for unpaper.
> Jens
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