I take back my comments about the dust removal being overeager. On closer
inspection these really are all specks of dust, just extremely tiny ones and,
in my case, the blur induced by the removal is actually more visible than the
dust that caused it.
On Sun, 13.08.17 19:12, Julian Hauser wrote:
Hello Klaus,
On Fri, 11.08.17 09:05, Klaus Kaempf wrote:
Hi Julian,
* Julian Hauser <jul...@julianhauser.com> [Aug 10. 2017 22:58]:
Hello everyone,
I'm using the Reflecta 10T scanner using the pieusb backend. It mostly works very well, thanks! One
thing I have noticed though is that if I enable the infrared scratch and dust removal option
"Clean image" in Xsane, the detected defects get painted over with a blurred dot. On film
negatives, which have a grainy structure, the results are clearly visible. I've uploaded an example
here: https://mis.julianhauser.com/index.php/s/MhSuFltcm0CLIMs. It would be very nice if the
corrections repaired the result taking into account the structure of the neighbouring areas (as for
example the "healing tool" in GIMP does).
Does the "overpainting" happen in the firmware of the scanner or is
that part of sane?
it's part of sane, resp. the pieusb backend. See
https://anonscm.debian.org/cgit/sane/sane-backends.git/tree/backend/pieusb_specific.c#n1321
where various sane_ir_* functions are called.
I've had a look at the functions that are responsible for the dust removal but
I have to admit I don't even understand the basic approach taken. Is the author
of those functions on the list? It would be nice if someone could explain me
roughly what is happening and where a change would have to be made.
I've also noticed that the scratch and dust removal seems to be a bit
overeager. If you look at the example image I linked to in the first email you
can see that the scan is littered with blurred circles. I scanned some photos
with scratch removal on and then off, and it is clear that most of the
corrections aren't of anything visible to the naked eye.
Two more things I've noticed with the scanner is that images always
come out reversed left-to-right
All images (color, greyscale, b&w) ? In all resolutions ?
All the ones I could test are reversed (but that is only various resolutions in
colour mode currently). Given that the same happened with the Reflecta
CrystalScan 7200 that I had earlier, I would say it's a general issue.
and greyscale scans make xsane crash. These things don't bother me much
as they are easily fixed with a script after scanning. I can send crash
logs if someone is interested in debugging this however.
Please do ! ;-)
Here's the log of an attempt to scan with xsane using greyscale:
https://pastebin.com/upMTt9HJ. I've realised that lineart and halftone do not
work either.
Thanks,
Julian
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