Strange quality using hpaio sane backend with a C4180

Discussion:

2007-10-04 16:59:00 UTC

Hi.

Since upgrading to HPLIP v1.7.7 I can finally use my HP C4180
scanner/printer device for scanning, but the outcome is rather ugly.

In order to give the developers the possibility, to "see" what I'm
talking about, I've prepared some image samples:

http://www.das-werkstatt.com/c4180/

These noisy-artifacts around the edges seem rather strange and
unnatural, so I thought I'd post this issue here.
Maybe someone could tell me if that's normal or not - or if that could
be fixed somehow (settings?).

Thanks,
PB

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Zbigniew Luszpinski

2007-10-04 18:22:51 UTC

Permalink

Post by PB
Since upgrading to HPLIP v1.7.7 I can finally use my HP C4180
scanner/printer device for scanning, but the outcome is rather ugly.

The current version is 2.7.9.

Post by PB
In order to give the developers the possibility, to "see" what I'm
http://www.das-werkstatt.com/c4180/
These noisy-artifacts around the edges seem rather strange and
unnatural, so I thought I'd post this issue here.
Maybe someone could tell me if that's normal or not - or if that could
be fixed somehow (settings?).

The scanimage gives sharper picture than WindowsXP. I prefer the one from
Linux and find it as better quality. If you want to have Windows "quality"
load gimp, then increase saturation and use blur effect on scanned picture.
This way you will get the same picture as in Windows.

zbiggy

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Suffield, David

2007-10-05 19:51:09 UTC

Permalink

Nice analyses on the image quality. :)

Our hpaio sane backend performs no up-stream image enhancements, so what
you see is uncompressed RGB or jpeg directly from the scanner.

The windows scanning solution does performs up-stream image enhancements
which may or may not be desirable.

In order to provide a simple open source scanning solution that can be
generalized for many HP devices, we prefer to leave image enhancements
to other open source tools like Gimp.

-dave

-----Original Message-----
Sent: Thursday, October 04, 2007 9:59 AM
Subject: [HPLIP-Devel] Strange quality using hpaio sane
backend with a C4180
Hi.
Since upgrading to HPLIP v1.7.7 I can finally use my HP C4180
scanner/printer device for scanning, but the outcome is rather ugly.
In order to give the developers the possibility, to "see"
http://www.das-werkstatt.com/c4180/
These noisy-artifacts around the edges seem rather strange
and unnatural, so I thought I'd post this issue here.
Maybe someone could tell me if that's normal or not - or if
that could be fixed somehow (settings?).
Thanks,
PB
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2007-10-06 12:56:35 UTC

Permalink

Thanks for your reply Dave!

hm... that's what I thought at first, since the windows-version is so
incredibly blurred.

However, I can't put my finger on it, but the characteristics of this
edge-noise just seem strange to me...

The edges of objects seem to be too distorted to fix by some
plain-vanilla GIMP filters (blur + sharpening afterwards?), since they
introduce a lot of aliasing effects - but if you say that the image is
"technically spoken" correct, I'll try to find a useful postprocessing
effect chain in GIMP to apply.

Thanks,
PB

Post by Suffield, David
Nice analyses on the image quality. :)
Our hpaio sane backend performs no up-stream image enhancements, so what
you see is uncompressed RGB or jpeg directly from the scanner.
The windows scanning solution does performs up-stream image enhancements
which may or may not be desirable.
In order to provide a simple open source scanning solution that can be
generalized for many HP devices, we prefer to leave image enhancements
to other open source tools like Gimp.
-dave

P.B.

2007-10-07 09:19:36 UTC

Permalink

@Dirk:
Thanks, I'll check out Median filters to see how they work out.

@All:
Meanwhile, I've did some post-processing tests in GIMP and found out
that a sequence of "Despeckle" and "Blur" work wonders!

Since this might be an issue for more than just the C4180 scanners, I
will post my results on the web - and maybe be able to provide some
script for automatically running scans through the GIMP for
post-processing. What do you think?

Although I totally agree to keep the post-procesing and the scanning
backend separate, I still think that a lot of users would be happy with
a "ready to use" image immediately after scanning. : )

Yours,
Pb

Hi
I think there's some sort of median filter that's being applied to the image in
order to neutralise eventual "dead pixels". The result of a median filter is
this sort of blurring.
Dirk

Post by PB
Thanks for your reply Dave!
hm... that's what I thought at first, since the windows-version is so
incredibly blurred.
However, I can't put my finger on it, but the characteristics of this
edge-noise just seem strange to me...
The edges of objects seem to be too distorted to fix by some
plain-vanilla GIMP filters (blur + sharpening afterwards?), since they
introduce a lot of aliasing effects - but if you say that the image is
"technically spoken" correct, I'll try to find a useful postprocessing
effect chain in GIMP to apply.
Thanks,
PB